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{{short description |Animals of the phylum Porifera}}
{{About |the phylum of aquatic animal |the porous cleaning tool |Sponge (tool) |other uses |Sponge (disambiguation)}}
{{pp-vandalism |small=yes}}
{{Good article}}
{{Automatic taxobox
|name=Sponges
|taxon=Porifera
|fossil_range=[[Ediacaran]]-present;<ref>{{cite journal |last1=Brasier |first1=Martin |last2=Green |first2=Owen |last3=Shields |first3=Graham |date=April 1997 |title=Ediacarian sponge spicule clusters from southwestern Mongolia and the origins of the Cambrian fauna |url=https://www.researchgate.net/publication/240669632 |format=PDF |journal=Geology |volume=25 |issue=4 |pages=303–306 |doi=10.1130/0091-7613(1997)025<0303:ESSCFS>2.3.CO;2 |bibcode=1997Geo....25..303B }}</ref> probable [[Cryogenian]] record,<ref>{{cite journal |last1=Gold |first1=David |last2=Grabenstatter |first2=Jonathan |last3=de Mendoza |first3=Alex |last4=Riesgo |first4=Ana |last5=Ruiz-Trillo |first5=Iñaki |last6=Summons |first6=Roger |title=Sterol and genomic analyses validate the sponge biomarker hypothesis |journal=PNAS |date=22 February 2016 |volume=113 |issue=10 |pages=2684–2689 |doi=10.1073/pnas.1512614113 |doi-access=free |pmid=26903629 |pmc=4790988 |bibcode=2016PNAS..113.2684G }}</ref> {{Long fossil range |earliest=650 |544 |0}}
|image=Aplysina archeri (Stove-pipe Sponge-pink variation).jpg
|image_caption=A [[Aplysina archeri|stove-pipe sponge]]
|authority=[[Robert Edmund Grant |Grant]], 1836
|subdivision_ranks=Classes
|subdivision=* [[Calcarea]]
* [[Demospongiae]]
* [[Hexactinellida]]
* [[Homoscleromorpha]]
* †[[Archaeocyatha]]
* †"[[Heteractinida]]" <small>([[paraphyletic]])</small>
* †[[Stromatoporoidea]]
* †[[Cribricyatha]]
* †[[Olgunidae]]{{small|(family)}}
 |synonyms=[[Parazoa]]/Ahistozoa (''sans'' [[Placozoa]])<ref>{{Cite journal |journal=Ethnolinguistic |last=Pajdzińska |first=A. |title=Animals die more shallowly: they aren't deceased, they're dead. Animals in the polish linguistic worldview and in contemporary life sciences |doi=10.17951/et.2017.29.135 |date=2018 |volume=29 |pages=147–161 |doi-access=free}}</ref>
}}

'''Sponges''' or '''sea sponges''' are primarily [[marine invertebrates]] of the [[animal]] [[phylum]] '''Porifera'''<ref>{{cite web |url=https://www.marinespecies.org/aphia.php?p=taxdetails&id=558 |title=Porifera |date=2024 |website= World Register of Marine Species |publisher=Flanders Marine Institute |access-date=8 May 2024}}</ref> ({{IPAc-en|p|ə|ˈ|r|ɪ|f|ər|ə|,|_|p|ɔː|-}}; meaning 'pore bearer'),<ref>{{Cite Merriam-Webster |porifera |accessdate=2024-05-12}}</ref> a [[Basal (phylogenetics) |basal]] [[clade]] and a [[sister taxon]] of the [[Eumetazoa |diploblasts]].<ref name="Feuda_2017">{{cite journal |last1=Feuda |first1=Roberto |last2=Dohrmann |first2=Martin |last3=Pett |first3=Walker |last4=Philippe |first4=Hervé |last5=Rota-Stabelli |first5=Omar |last6=Lartillot |first6=Nicolas |last7=Wörheide |first7=Gert |last8=Pisani |first8=Davide |title=Improved Modeling of Compositional Heterogeneity Supports Sponges as Sister to All Other Animals |journal=Current Biology |volume=27 |issue=24 |pages=3864–3870.e4 |date=December 2017 |pmid=29199080 |doi=10.1016/j.cub.2017.11.008 |doi-access=free |bibcode=2017CBio...27E3864F }}</ref> They are [[sessility (motility) |sessile]] [[filter feeder]]s that are bound to the [[seabed]], and are one of the most ancient members of [[macrobenthos]], with many historical species being important [[sponge reef |reef]]-building organisms.

Sponges are [[multicellular organism]]s consisting of jelly-like [[mesohyl]] sandwiched between two thin layers of [[cell (biology) |cells]], and usually have tube-like bodies full of pores and channels that allow water to circulate through them. They have unspecialized cells that can [[cellular differentiation |transform into other types]] and that often migrate between the main cell layers and the mesohyl in the process. They do not have complex [[nervous system |nervous]],<ref name="Moroz_2022">{{cite journal |last1=Moroz |first1=L.L. |last2=Romanova |first2=D.Y. |title=Alternative neural systems: What is a neuron? (Ctenophores, sponges and placozoans) |journal=Frontiers in Cell and Developmental Biology |volume=10 |pages=1071961 |date=23 December 2022 |pmid=36619868 |pmc=9816575 |doi=10.3389/fcell.2022.1071961 |doi-access=free }}</ref> [[digestive system |digestive]] or [[circulatory system]]s. Instead, most rely on maintaining a constant water flow through their bodies to obtain food and [[oxygen]] and to remove wastes, usually via [[flagella]] movements of the so-called "[[collar cell]]s".

Sponges are believed to have been the first [[outgroup (cladistics) |outgroup]] to branch off the [[evolutionary tree]] from the [[Urmetazoan |last common ancestor of all animals]],<ref name="Feuda_2017"/> with fossil evidence of primitive sponges such as ''[[Otavia]]'' from as early as the [[Tonian]] [[geologic period |period]] (around 800&nbsp;[[million years ago |Mya]]). The branch of [[zoology]] that studies sponges is spongiology.<ref>{{cite Merriam-Webster |Spongiology |access-date=27 December 2017}}</ref>{{toclimit |3}}

== Etymology ==
The term ''sponge'' derives from the [[Ancient Greek]] word {{wikt-lang|grc|σπόγγος}} {{grc-transl|σπόγγος}}.<ref>{{Cite dictionary |title=σπόγγος |url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:alphabetic+letter=*s111:entry+group=61:entry=spo/ggos |last1=Liddell |first1=Henry George |last2=Scott |first2=Robert |dictionary=A Greek-English Lexicon |year=1940 |via=Perseus |access-date=5 September 2021 |archive-url=https://web.archive.org/web/20210905062852/https://www.perseus.tufts.edu/hopper/text?doc=Perseus:text:1999.04.0057:alphabetic+letter=*s111:entry+group=61:entry=spo/ggos |archive-date=5 September 2021 |url-status=live}}</ref> The [[scientific name]] ''Porifera'' is a [[neuter gender|neuter]] [[plural]] of the [[Modern Latin]] term ''porifer'', which comes from the [[root (linguistics)|root]]s ''porus'' meaning "pore, opening", and ''-fer'' meaning "bearing or carrying".

== Overview ==
[[File:Reef3859 - Flickr - NOAA Photo Library.jpg|thumb|right|Sponge [[biodiversity]] and [[morphotype]]s at the lip of a wall site in {{convert|60|ft|m|-1}} of water. Included are the yellow tube sponge, ''[[Aplysina fistularis]]'', the purple vase sponge, ''[[Niphates digitalis]]'', the red encrusting sponge, ''[[Spirastrella coccinea]]'', and the gray rope sponge, ''[[Callyspongia]]'' sp.]]

Sponges are similar to other animals in that they are [[Multicellular organism|multicellular]], [[heterotroph]]ic, lack [[cell wall]]s and produce [[sperm cell]]s. Unlike other animals, they lack true [[Tissue (biology)|tissues]]<ref name="Hooper">{{cite web |url= https://www.qm.qld.gov.au/microsites/biodiscovery/03sponges-and-corals/structure-of-sponges.html |title=Structure of Sponges |last= Hooper |first=J. |year=2018 |website=Queensland Museum |access-date=27 September 2019 |archive-url=https://web.archive.org/web/20190926205031/https://www.qm.qld.gov.au/microsites/biodiscovery/03sponges-and-corals/structure-of-sponges.html |archive-date=26 September 2019 |url-status=dead }}</ref> and [[Organ (anatomy)|organs]].<ref>{{cite journal |last1=Thacker |first1=Robert W. |last2=Díaz |first2=Maria Cristina |last3=Kerner |first3=Adeline |last4=Vignes-Lebbe |first4=Régine |last5=Segerdell |first5=Erik |last6=Haendel |first6=Melissa A. |last7=Mungall |first7=Christopher J. |title=The Porifera Ontology (PORO): enhancing sponge systematics with an anatomy ontology |journal=Journal of Biomedical Semantics |volume=5 |issue=1 |pages=39 |date=8 September 2014 |pmid=25276334 |pmc=4177528 |doi=10.1186/2041-1480-5-39 |doi-access=free }}</ref> Some of them are radially symmetrical, but most are asymmetrical. The shapes of their bodies are adapted for maximal efficiency of water flow through the central cavity, where the water deposits nutrients and then leaves through a hole called the [[osculum]]. The [[unicellular|single-celled]] [[choanoflagellate]]s resemble the [[choanocyte]] cells of sponges which are used to drive their water flow systems and capture most of their food. This along with phylogenetic studies of ribosomal molecules have been used as morphological evidence to suggest sponges are the sister group to the rest of animals.<ref name="Collins_1998">{{cite journal |last=Collins |first=A.G. |title=Evaluating multiple alternative hypotheses for the origin of Bilateria: an analysis of 18S rRNA molecular evidence |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=95 |issue=26 |pages=15458–63 |date=December 1998 |pmid=9860990 |pmc=28064 |doi=10.1073/pnas.95.26.15458 |bibcode=1998PNAS...9515458C |doi-access=free }}</ref> A great majority are marine (salt-water) species, ranging in habitat from tidal zones to depths exceeding {{convert|8,800|m|mi|abbr=on}}, though there are freshwater species. All adult sponges are [[Sessility (motility)|sessile]], meaning that they attach to an underwater surface and remain fixed in place (i.e., do not travel). While in their [[larvae|larval stage]] of life, they are [[motility|motile]].

Many sponges have internal skeletons of spicules (skeletal-like fragments of [[calcium carbonate]] or [[silicon dioxide]]), and/or [[spongin]] (a modified type of collagen protein).<ref name="Hooper"/> An internal gelatinous [[matrix (biology)|matrix]] called mesohyl functions as an [[endoskeleton]], and it is the only skeleton in soft sponges that encrust such hard surfaces as rocks. More commonly, the mesohyl is stiffened by [[Biomineralization|mineral]] [[sponge spicule|spicules]], by spongin fibers, or both. Most sponges (over 90% of all known species) are [[demosponge]]s, which have the widest range of habitats (including all freshwater ones); they use spongin, [[silica]] spicules, or both, and some species have calcium carbonate [[exoskeleton]]s. [[Calcareous sponge|Calcarean]]s have calcium carbonate spicules and, in some species, calcium carbonate exoskeletons; they are restricted to relatively shallow marine waters where production of calcium carbonate is easiest.<ref name="Bergquist_1978"/>{{rp|179}} The fragile [[glass sponge|hexactinellids or glass sponge]]s use "[[scaffolding]]" of silica spicules and are restricted to polar regions or ocean depths where predators are rare. Fossils of all of these types have been found in rocks dated from {{ma|580}}. In addition [[Archaeocyathid]]s, whose fossils are common in rocks from {{ma|530|490}}, are now regarded as a type of sponge. The smallest class of extant sponges are [[Homosclerophorida|homoscleromorphs]], which either have calcium carbonate spicules like the calcereans or are aspiculate, and found in shaded marine environments like caves and overhangs.

Although most of the approximately 5,000–10,000&nbsp;known species of sponges feed on [[bacteria]] and other microscopic food in the water, some host [[photosynthesis|photosynthesizing]] microorganisms as [[endosymbiont]]s, and these alliances often produce more food and oxygen than they consume. A few species of sponges that live in food-poor environments have evolved as [[carnivore]]s that prey mainly on small [[crustacean]]s.<ref>{{cite journal |last1=Vacelet |first1=J. |last2=Duport |first2=E. |title=Prey capture and digestion in the carnivorous sponge ''Asbestopluma hypogea'' (Porifera: Demospongiae)|year=2004|journal=[[Zoomorphology]]|volume=123|issue=4|pages=179–190|s2cid=24484610 |doi=10.1007/s00435-004-0100-0 }}</ref>

Most sponges reproduce [[sexual reproduction|sexually]], but they can also reproduce asexually. Sexually reproducing species release [[sperm]] cells into the water to fertilize [[ovum|ova]] released or retained by its mate or "mother"; the fertilized eggs develop into [[larva]]e which swim off in search of places to settle.<ref name="Bergquist_1978">{{Cite book |last=Bergquist |first=P. R. |year=1978 |title=Sponges |publisher=Hutchinson |location=London |isbn=978-0-520-03658-1}}</ref>{{rp|183–185}} Sponges are known for regenerating from fragments that are broken off, although this only works if the fragments include the right types of cells. Some species reproduce by budding. When environmental conditions become less hospitable to the sponges, for example as temperatures drop, many freshwater species and a few marine ones produce [[gemmule]]s, "survival pods" of unspecialized cells that remain dormant until conditions improve; they then either form completely new sponges or recolonize the skeletons of their parents.<ref name="Bergquist_1978"/>{{rp|120–127}}

[[File:Choanoflagellate and choanocyte.png|thumb|upright=1.8|Cells of the protist choanoflagellate clade closely resemble sponge choanocyte cells. Beating of choanocyte [[flagella]] draws water through the sponge so that nutrients can be extracted and waste removed.<ref>Clark, M.A.; Choi, J.; Douglas, M. (2018) [https://web.archive.org/web/20191011015411/https://d3bxy9euw4e147.cloudfront.net/oscms-prodcms/media/documents/Biology2e-OP.pdf ''Biology 2e''], page 776, ''OpenStax''. {{ISBN|978-1-947172-52-4}}.</ref>]]

The few species of demosponge that have entirely soft fibrous skeletons with no hard elements have been used by humans over thousands of years for several purposes, including as padding and as cleaning tools. By the 1950s, though, these had been [[overfishing|overfished]] so heavily that the industry almost collapsed, and most sponge-like materials are now synthetic. Sponges and their microscopic endosymbionts are now being researched as possible sources of medicines for treating a wide range of diseases. [[Dolphin]]s have been observed using sponges as tools while [[foraging]].<ref name="Krutzen_2005"/>

== Distinguishing features ==

{{Further|Cnidaria|Ctenophore}}

Sponges constitute the [[phylum]] Porifera, and have been defined as [[Sessility (motility)|sessile]] [[metazoa]]ns (multicelled immobile animals) that have water intake and outlet openings connected by chambers lined with [[choanocyte]]s, cells with whip-like flagella.<ref name="Bergquist_1978"/>{{rp|29}} However, a few carnivorous sponges have lost these water flow systems and the choanocytes.<ref name="Bergquist_1978"/>{{rp|39}}<ref name="Hooper_2002">{{cite book |author1=Hooper, J. N. A. |author2=Van Soest, R. W. M. |author3=Debrenne, F. |contribution=Phylum Porifera Grant, 1836|pages=9–14 |editor1=Hooper, J. N. A. |editor2=Van Soest, R. W. M. |title=Systema Porifera: A Guide to the Classification of Sponges |publisher=Kluwer Academic/Plenum |location=New York |url={{google books |plainurl=y |id=OQoxzqjQXWEC|page=220}}|year=2002 |isbn=978-0-306-47260-2}}</ref> All known living sponges can remold their bodies, as most types of their cells can move within their bodies and a few can change from one type to another.<ref name="Hooper_2002"/><ref name="Ruppert_2004">{{cite book |last1=Ruppert |first1=Edward E. |last2=Fox |first2=Richard S. |last3=Barnes |first3=Robert D. |title=Invertebrate Zoology |publisher=Brooks / [[COLE Publishing]] |edition=7th |isbn=978-0-03-025982-1 |year=2004 |url-access=registration |url=https://archive.org/details/isbn_9780030259821 |pages=76–97}}</ref>

Even if a few sponges are able to produce mucus – which acts as a microbial barrier in all other animals – no sponge with the ability to secrete a functional mucus layer has been recorded. Without such a mucus layer their living tissue is covered by a layer of microbial symbionts, which can contribute up to 40–50% of the sponge wet mass. This inability to prevent microbes from penetrating their porous tissue could be a major reason why they have never evolved a more complex anatomy.<ref>{{cite journal |last1=Bakshani |first1=Cassie R. |last2=Morales-Garcia |first2=Ana L. |last3=Althaus |first3=Mike |last4=Wilcox |first4=Matthew D. |last5=Pearson |first5=Jeffrey P. |last6=Bythell |first6=John C. |last7=Burgess |first7=J. Grant |title=Evolutionary conservation of the antimicrobial function of mucus: a first defence against infection |journal=npj Biofilms and Microbiomes |volume=4 |issue=1 |page=14 |date=2018-07-04 |pmid=30002868 |pmc=6031612 |doi=10.1038/s41522-018-0057-2 }}</ref>

Like [[cnidaria]]ns (jellyfish, etc.) and [[Ctenophora|ctenophores]] (comb jellies), and unlike all other known metazoans, sponges' bodies consist of a non-living jelly-like mass ([[mesohyl]]) sandwiched between two main layers of cells.<ref name="Bergquist_1998"/><ref name="Hinde_2001">{{cite book |last=Hinde |first=R. T. |year=1998 |chapter=The Cnidaria and Ctenophora|pages=28–57 |editor-last=Anderson |editor-first=D. T. |title=Invertebrate Zoology |publisher=[[Oxford University Press]] |isbn=978-0-19-551368-4}}</ref> Cnidarians and ctenophores have simple nervous systems, and their cell layers are bound by internal connections and by being mounted on a basement membrane (thin fibrous mat, also known as "[[basal lamina]]").<ref name="Hinde_2001"/> Sponges do not have a nervous system similar to that of vertebrates but may have one that is quite different.<ref name="Moroz_2022"/> Their middle jelly-like layers have large and varied populations of cells, and some types of cells in their outer layers may move into the middle layer and change their functions.<ref name="Ruppert_2004"/>

{|class="wikitable" <!-- width="45%" --> style="margin-left:4px"
|-
!  !! Sponges<ref name="Ruppert_2004"/><ref name="Bergquist_1998"/> !! [[Cnidarian]]s and [[ctenophore]]s<ref name="Hinde_2001"/>
|-
! Nervous system
|No/Yes ||Yes, simple
|-
! Cells in each layer bound together
|No, except that [[Homoscleromorpha]] have basement membranes.<ref name="Exposito_2002"/> ||Yes: inter-cell connections; basement membranes
|-
! Number of cells in middle "jelly" layer
|Many ||Few
|-
! Cells in outer layers can move inwards and change functions
|Yes ||No
|}

== Basic structure ==
<!--[[File:Tide pools sponge.jpg|A pink sponge in a [[tide pool]]|thumb]]
[[File:Aphrocallistes vastus.jpg|thumb|''Aphrocallistes vastus'' (cloud sponge) is a type of glass sponge. They are very fragile, as they are made out of tiny glass crystals ([[hydrated silica]] dioxide).<ref>{{cite web|url=http://www.biology.ualberta.ca/faculty/sally_leys/uploads/personal/Glass%20sponge%20ecology.htm|title=Studies in Life Sciences, University of Alberta: Glass Sponge Ecology|work=Department of Biological Sciences|access-date=2008-03-16|archive-url=https://web.archive.org/web/20120715083546/http://www.biology.ualberta.ca/faculty/sally_leys/uploads/personal/Glass%20sponge%20ecology.htm|archive-date=July 15, 2012|url-status=live}}</ref>]]-->

=== Cell types ===

{{anchor|Ostium (sponges)}}
{{Annotated image/Porifera cell types}}
A sponge's body is hollow and is held in shape by the [[mesohyl]], a jelly-like substance made mainly of [[collagen]] and reinforced by a dense network of fibers also made of collagen. 18 distinct cell types have been identified.<ref>{{cite journal |last1=Musser |first1=Jacob M. |last2=Schippers |first2=Klaske J. |last3=Nickel |first3=Michael |last4=Mizzon |first4=Giulia |last5=Kohn |first5=Andrea B. |last6=Pape |first6=Constantin |last7=Ronchi |first7=Paolo |last8=Papadopoulos |first8=Nikolaos |last9=Tarashansky |first9=Alexander J. |last10=Hammel |first10=Jörg U. |last11=Wolf |first11=Florian |last12=Liang |first12=Cong |last13=Hernández-Plaza |first13=Ana |last14=Cantalapiedra |first14=Carlos P. |last15=Achim |first15=Kaia |last16=Schieber |first16=Nicole L. |last17=Pan |first17=Leslie |last18=Ruperti |first18=Fabian |last19=Francis |first19=Warren R. |last20=Vargas |first20=Sergio |last21=Kling |first21=Svenja |last22=Renkert |first22=Maike |last23=Polikarpov |first23=Maxim |last24=Bourenkov |first24=Gleb |last25=Feuda |first25=Roberto |last26=Gaspar |first26=Imre |last27=Burkhardt |first27=Pawel |last28=Wang |first28=Bo |last29=Bork |first29=Peer |last30=Beck |first30=Martin |last31=Schneider |first31=Thomas R. |last32=Kreshuk |first32=Anna |last33=Wörheide |first33=Gert |last34=Huerta-Cepas |first34=Jaime |last35=Schwab |first35=Yannick |last36=Moroz |first36=Leonid L. |last37=Arendt |first37=Detlev |display-authors=6 |title=Profiling cellular diversity in sponges informs animal cell type and nervous system evolution |journal=Science |volume=374 |issue=6568 |pages=717–723 |date=November 2021 |pmid=34735222 |pmc=9233960 |doi=10.1126/science.abj2949 |bibcode=2021Sci...374..717M }}</ref> The inner surface is covered with [[choanocyte]]s, cells with cylindrical or conical collars surrounding one [[flagellum]] per choanocyte. The wave-like motion of the whip-like flagella drives water through the sponge's body. All sponges have '''ostia''', channels leading to the interior through the mesohyl, and in most sponges these are controlled by tube-like [[porocytes]] that form closable inlet valves. [[Pinacocyte]]s, plate-like cells, form a single-layered external skin over all other parts of the mesohyl that are not covered by choanocytes, and the pinacocytes also digest food particles that are too large to enter the ostia,<ref name="Ruppert_2004"/><ref name="Bergquist_1998"/> while those at the base of the animal are responsible for anchoring it.<ref name="Bergquist_1998"/>

Other types of cells live and move within the mesohyl:<ref name="Ruppert_2004"/><ref name="Bergquist_1998"/>
* [[Lophocyte]]s are [[amoeba]]-like cells that move slowly through the mesohyl and secrete collagen fibres.
* [[Collencyte]]s are another type of collagen-producing cell.
* [[Rhabdiferous]] cells secrete [[polysaccharide]]s that also form part of the mesohyl.
* [[Oocyte]]s and [[spermatocyte]]s are reproductive cells.
* [[Sclerocyte]]s secrete the mineralized [[sponge spicule|spicules]] ("little spines") that form the [[skeleton]]s of many sponges and in some species provide some defense against predators.
* In addition to or instead of sclerocytes, [[demosponge]]s have [[spongocyte]]s that secrete a form of collagen that [[polymer]]izes into [[spongin]], a thick fibrous material that stiffens the mesohyl.
* [[Myocyte]]s ("muscle cells") conduct signals and cause parts of the animal to contract.
* "Grey cells" act as sponges' equivalent of an [[immune system]].
* [[Archaeocytes]] (or [[amoebocytes]]) are [[amoeba]]-like cells that are [[totipotent]], in other words, each is capable of transformation into any other type of cell. They also have important roles in feeding and in clearing debris that block the ostia.

Many larval sponges possess neuron-less [[eye]]s that are based on [[cryptochrome]]s. They mediate phototaxic behavior.<ref>{{cite journal |last1=Rivera |first1=A.S. |last2=Ozturk |first2=N. |last3=Fahey |first3=B. |last4=Plachetzki |first4=D.C. |last5=Degnan |first5=B.M. |last6=Sancar |first6=A. |last7=Oakley |first7=T.H. |title=Blue-light-receptive cryptochrome is expressed in a sponge eye lacking neurons and opsin |journal=The Journal of Experimental Biology |volume=215 |issue=Pt 8 |pages=1278–86 |date=April 2012 |pmid=22442365 |pmc=3309880 |doi=10.1242/jeb.067140 |bibcode=2012JExpB.215.1278R }}</ref>

[[Glass sponge]]s present a distinctive variation on this basic plan. Their spicules, which are made of [[silica]], form a [[scaffolding]]-like framework between whose rods the living tissue is suspended like a [[Spider web|cobweb]] that contains most of the cell types.<ref name="Ruppert_2004"/> This tissue is a [[Hexactinellid#Syncytia|syncytium]] that in some ways behaves like many cells that share a single external [[Cell membrane|membrane]], and in others like a single cell with multiple [[cell nucleus|nuclei]].

=== Water flow and body structures ===

{{Annotated image |float={{{float|right}}} |caption=[[Porifera]] body structures<ref>{{cite book
|last1=Ruppert|first1=Edward E.|last2=Fox|first2=Richard S.|last3=Barnes|first3=Robert D. |title=Invertebrate Zoology |publisher=Brooks / Cole |edition=7th |isbn=978-0-03-025982-1 |date=2004 |page=78 |ref=none}}</ref> |image=Porifera body structures 01.png |width=280 |image-width=280 |height=205
|annotations=
{{Annotation|5|150|'''Asconoid'''}}
{{Annotation|105|150|'''Syconoid'''}}
{{Annotation|205|150|'''Leuconoid'''}}
{{Annotation|5|170|<span style{{=}}"background-color:yellow; border: solix 1px silver">&nbsp;&nbsp;&nbsp;</span> [[Pinacocyte]]s}}
{{Annotation|5|190|<span style{{=}}"background-color:red; border:solix 1px silver">&nbsp;&nbsp;&nbsp;</span> [[Choanocyte]]s}}
{{Annotation|145|170|<span style{{=}}"background-color:#c0c0c0; border:solix 1px silver">&nbsp;&nbsp;&nbsp;</span> [[Mesohyl]]}}
{{Annotation|145|190|<span style{{=}}"background-color:#00ffff; border: solix 1px silver">&nbsp;&nbsp;&nbsp;</span> Water flow}}
}}

Most sponges work rather like [[chimney]]s: they take in water at the bottom and eject it from the [[osculum]] at the top. Since ambient currents are faster at the top, the suction effect that they produce by [[Bernoulli's principle]] does some of the work for free. Sponges can control the water flow by various combinations of wholly or partially closing the osculum and ostia (the intake pores) and varying the beat of the flagella, and may shut it down if there is a lot of sand or silt in the water.<ref name="Ruppert_2004"/>

Although the layers of [[pinacocyte]]s and [[choanocyte]]s resemble the [[epithelia]] of more complex animals, they are not bound tightly by cell-to-cell connections or a basal lamina (thin fibrous sheet underneath). The flexibility of these layers and re-modeling of the mesohyl by lophocytes allow the animals to adjust their shapes throughout their lives to take maximum advantage of local water currents.<ref name="Ruppert_2004"/>{{rp|83}}

The simplest body structure in sponges is a tube or vase shape known as "asconoid", but this severely limits the size of the animal. The body structure is characterized by a stalk-like spongocoel surrounded by a single layer of choanocytes. If it is simply scaled up, the ratio of its volume to surface area increases, because surface increases as the square of length or width while volume increases proportionally to the cube. The amount of tissue that needs food and [[oxygen]] is determined by the volume, but the pumping capacity that supplies food and oxygen depends on the area covered by choanocytes. Asconoid sponges seldom exceed {{convert|1|mm|in|abbr=on}} in diameter.<ref name="Ruppert_2004"/>

[[File:Sea sponge diagram.svg|thumb|250px|left|Diagram of a syconoid sponge]]

Some sponges overcome this limitation by adopting the "syconoid" structure, in which the body wall is [[pleat]]ed. The inner pockets of the pleats are lined with choanocytes, which connect to the outer pockets of the pleats by ostia. This increase in the number of choanocytes and hence in pumping capacity enables syconoid sponges to grow up to a few centimeters in diameter.

{{anchor|leuconoid}}The "leuconoid" pattern boosts pumping capacity further by filling the interior almost completely with mesohyl that contains a network of chambers lined with choanocytes and connected to each other and to the water intakes and outlet by tubes. Leuconid sponges grow to over {{convert|1|m|ft|abbr=on}} in diameter, and the fact that growth in any direction increases the number of choanocyte chambers enables them to take a wider range of forms, for example, "encrusting" sponges whose shapes follow those of the surfaces to which they attach. All freshwater and most shallow-water marine sponges have leuconid bodies. The networks of water passages in [[glass sponge]]s are similar to the leuconid structure.<ref name="Ruppert_2004"/>

In all three types of structure, the cross-section area of the choanocyte-lined regions is much greater than that of the intake and outlet channels. This makes the flow slower near the choanocytes and thus makes it easier for them to trap food particles.<ref name="Ruppert_2004"/> For example, in ''[[Leuconia]]'', a small leuconoid sponge about {{convert|10|cm|in}} tall and {{convert|1|cm|in}} in diameter, water enters each of more than 80,000 intake canals at 6&nbsp;cm per ''minute''. However, because ''Leuconia'' has more than 2&nbsp;million flagellated chambers whose combined diameter is much greater than that of the canals, water flow through chambers slows to 3.6&nbsp;cm per ''hour'', making it easy for choanocytes to capture food. All the water is expelled through a single [[osculum]] at about 8.5&nbsp;cm per ''second'', fast enough to carry waste products some distance away.<ref>{{cite book |author1=Hickman, C.P. |author2=Roberts, L.S. |author3=Larson, A. |year=2001 |title=Integrated Principles of Zoology |edition=11th |publisher=[[McGraw-Hill]] |location=New York |isbn=978-0-07-290961-6 |page=247}}</ref>

[[File:Porifera calcifying 01.png|thumb|Sponge with calcium carbonate skeleton.<ref name="Ruppert_2004"/>
{{legend-col
|{{legend|yellow|[[Pinacocyte]]}}
|{{legend|red|[[Choanocyte]]}}
|{{legend|lime|[[Archeocyte]]s and other cells in [[mesohyl]]}}
|{{legend|#d6d6d6|Mesohyl}}
|{{legend|#5d5d5d|Spicules}}
|{{legend|#ff8000|[[Calcium carbonate]]}}
|{{legend|#804000|Seabed / rock}}
|{{legend|#00ffff|Water flow}}
}}
]]

=== Skeleton ===

In zoology, a [[skeleton]] is any fairly rigid structure of an animal, irrespective of whether it has joints and irrespective of whether it is [[biomineralization|biomineralized]]. The mesohyl functions as an [[endoskeleton]] in most sponges, and is the only skeleton in soft sponges that encrust hard surfaces such as rocks. More commonly the mesohyl is stiffened by mineral [[sponge spicule|spicules]], by spongin fibers or both. Spicules, which are present in most but not all species,<ref>{{Cite web |url=http://species-identification.org/species.php?species_group=sponges&id=259 |title=Marine Species Identification Portal: Halisarca dujardini|website=species-identification.org |access-date=2019-08-02 |archive-date=2020-10-17 |archive-url=https://web.archive.org/web/20201017130847/http://species-identification.org/species.php?species_group=sponges&id=259 |url-status=dead}}</ref> may be made of [[silica]] or calcium carbonate, and vary in shape from simple rods to three-dimensional "stars" with up to six rays. Spicules are produced by [[sclerocyte]] cells,<ref name="Ruppert_2004"/> and may be separate, connected by joints, or fused.<ref name="Hooper_2002"/>

Some sponges also secrete [[exoskeleton]]s that lie completely outside their organic components. For example, [[sclerosponge]]s ("hard sponges") have massive calcium carbonate exoskeletons over which the organic matter forms a thin layer with [[choanocyte]] chambers in pits in the mineral. These exoskeletons are secreted by the [[pinacocyte]]s that form the animals' skins.<ref name="Ruppert_2004"/>

== Vital functions ==

[[File:Spongia officinalis.jpg|thumb|right|''[[Spongia officinalis]]'', "the kitchen sponge", is dark grey when alive.]]

=== Movement ===

Although adult sponges are fundamentally [[Sessility (zoology)|sessile]] animals, some marine and freshwater species can move across the sea bed at speeds of {{convert|1|-|4|mm|in|abbr=on}} per day, as a result of [[amoeba]]-like movements of [[pinacocyte]]s and other cells. A few species can contract their whole bodies, and many can close their [[osculum|oscula]] and [[wikt:ostium|ostia]]. Juveniles drift or swim freely, while adults are stationary.<ref name="Ruppert_2004"/>

=== Respiration, feeding and excretion ===

[[File:Venus Flower Basket.jpg|thumb|''[[Euplectella aspergillum]]'', a [[glass sponge]] known as "Venus's flower basket"]]

Sponges do not have distinct [[circulatory]], [[respiratory]], [[digestion|digestive]], and [[excretory]] systems – instead, the water flow system supports all these functions. They [[filter feeding|filter]] food particles out of the water flowing through them. Particles larger than 50&nbsp;micrometers cannot enter the [[wikt:ostium|ostia]] and [[pinacocyte]]s consume them by [[phagocytosis]] (engulfing and intracellular digestion). Particles from 0.5&nbsp;μm to 50&nbsp;μm are trapped in the ostia, which taper from the outer to inner ends. These particles are consumed by pinacocytes or by [[archaeocyte]]s which partially extrude themselves through the walls of the ostia. Bacteria-sized particles, below 0.5&nbsp;micrometers, pass through the ostia and are caught and consumed by [[choanocyte]]s.<ref name="Ruppert_2004"/> Since the smallest particles are by far the most common, choanocytes typically capture 80% of a sponge's food supply.<ref name="Bergquist_2001">{{cite book |contribution=Porifera (Sponges) |last=Bergquist |first=P.R. |title=Encyclopedia of Life Sciences |year=2001 |publisher= John Wiley & Sons |doi=10.1038/npg.els.0001582 |isbn=978-0-470-01617-6}}</ref> Archaeocytes transport food packaged in [[Vesicle (biology)|vesicles]] from cells that directly digest food to those that do not. At least one species of sponge has internal fibers that function as tracks for use by nutrient-carrying archaeocytes,<ref name="Ruppert_2004"/> and these tracks also move inert objects.<ref name="Bergquist_1998"/>

It used to be claimed that [[glass sponge]]s could live on nutrients dissolved in sea water and were very averse to silt.<ref name="Krautter_1998">{{cite journal |last=Krautter |first=M. |title=Ecology of siliceous sponges: Application to the environmental interpretation of the Upper Jurassic sponge facies (Oxfordian) from Spain |journal=[[Journal of Iberian Geology|Cuadernos de Geología Ibérica]] |pages=223–239 |year=1998 |volume=24 |url=http://www.ucm.es/BUCM/revistas/geo/16986180/articulos/JIGE9898110223A.PDF |archive-url=https://web.archive.org/web/20090319205858/http://www.ucm.es/BUCM/revistas/geo/16986180/articulos/JIGE9898110223A.PDF |archive-date=March 19, 2009 |access-date=2008-10-10 |url-status=dead }}</ref> However, a study in 2007 found no evidence of this and concluded that they extract bacteria and other micro-organisms from water very efficiently (about 79%) and process suspended sediment grains to extract such prey.<ref>{{cite journal |doi=10.4319/lo.2007.52.1.0428 |author1=Yahel, G. |author2=Whitney, F. |author3=Reiswig, H.M. |author4=Eerkes-Medrano, D.I. |author5=Leys, S.P. |year=2007 |title=In situ feeding and metabolism of glass sponges (Hexactinellida, Porifera) studied in a deep temperate fjord with a remotely operated submersible |journal=[[Limnology and Oceanography]] |volume=52|issue=1|pages=428–440|citeseerx=10.1.1.597.9627|bibcode=2007LimOc..52..428Y|s2cid=86297053 }}</ref> Collar bodies digest food and distribute it wrapped in vesicles that are transported by [[dynein]] "motor" molecules along bundles of [[microtubule]]s that run throughout the [[syncytium]].<ref name="Ruppert_2004"/>

Sponges' cells absorb oxygen by [[diffusion]] from water into cells as water flows through body, into which [[carbon dioxide]] and other soluble waste products such as [[ammonia]] also diffuse. Archeocytes remove mineral particles that threaten to block the ostia, transport them through the mesohyl and generally dump them into the outgoing water current, although some species incorporate them into their skeletons.<ref name="Ruppert_2004"/>

=== Carnivorous sponges ===

[[File:Chondrocladia lampadiglobus.jpg|thumb|The carnivorous ping-pong tree sponge, ''[[Chondrocladia]] lampadiglobus''<ref>{{cite journal |last1=Van Soest |first1=Rob W. M. |last2=Boury-Esnault |first2=Nicole |last3=Vacelet |first3=Jean |last4=Dohrmann |first4=Martin |last5=Erpenbeck |first5=Dirk |last6=De Voogd |first6=Nicole J. |last7=Santodomingo |first7=Nadiezhda |last8=Vanhoorne |first8=Bart |last9=Kelly |first9=Michelle |last10=Hooper |first10=John N. A. |title=Global diversity of sponges (Porifera) |journal=PLOS ONE |volume=7 |issue=4 |pages=e35105 |year=2012 |pmid=22558119 |pmc=3338747 |doi=10.1371/journal.pone.0035105 |doi-access=free |bibcode=2012PLoSO...735105V |author-link9=Michelle Kelly (marine scientist) }}</ref>]]

In waters where the supply of food particles is very poor, some species prey on [[crustacea]]ns and other small animals. As of 2014, a total of 137 species had been discovered.<ref>{{cite news|date=April 19, 2014 |url=http://www.cbc.ca/news/canada/british-columbia/4-new-species-of-killer-sponges-discovered-off-pacific-coast-1.2615509 |title=4 new species of 'killer' sponges discovered off Pacific coast |work=[[CBC News]] |access-date=2014-09-04 |url-status=live |archive-url=https://web.archive.org/web/20140419143139/http://www.cbc.ca/news/canada/british-columbia/4-new-species-of-killer-sponges-discovered-off-pacific-coast-1.2615509 |archive-date=April 19, 2014 }}</ref> Most belong to the [[family (biology)|family]] [[Cladorhizidae]], but a few members of the [[Guitarridae]] and [[Esperiopsidae]] are also carnivores.<ref name="Vacelet_2008"/> In most cases, little is known about how they actually capture prey, although some species are thought to use either sticky threads or hooked [[sponge spicule|spicules]].<ref name="Vacelet_2008"/><ref>{{cite journal|last= Watling |first=L. |title=Predation on copepods by an Alaskan cladorhizid sponge |journal=[[Journal of the Marine Biological Association of the United Kingdom]] |year= 2007|volume=87 |pages=1721–1726 |doi=10.1017/S0025315407058560|issue=6 |bibcode=2007JMBUK..87.1721W |s2cid=86588792}}</ref> Most carnivorous sponges live in deep waters, up to {{convert|8840|m|mi|abbr=on}},<ref name="Vacelet_1995">{{cite journal |last1= Vacelet |first1=J. |last2=Boury-Esnault |first2=N. |title=Carnivorous sponges|journal=Nature|volume=373|pages=333–335|year=1995|doi=10.1038/373333a0|issue=6512|bibcode=1995Natur.373..333V|s2cid=4320216|doi-access=free}}</ref> and the development of deep-ocean exploration techniques is expected to lead to the discovery of several more.<ref name="Ruppert_2004"/><ref name="Vacelet_2008">{{cite journal |last1=Vacelet |first1=J. |title=A new genus of carnivorous sponges (Porifera: Poecilosclerida, Cladorhizidae) from the deep N-E Pacific, and remarks on the genus ''Neocladia''|journal=[[Zootaxa]]|url=http://www.mapress.com/zootaxa/2008/f/z01752p065f.pdf |archive-url=https://web.archive.org/web/20080906190452/http://www.mapress.com/zootaxa/2008/f/z01752p065f.pdf |archive-date=2008-09-06 |url-status=live|volume=1752|pages=57–65|year=2008|access-date=2008-10-31|doi=10.11646/zootaxa.1752.1.3}}</ref> However, one species has been found in [[Mediterranean]] caves at depths of {{convert|17|-|23|m|ft|abbr=on}}, alongside the more usual [[filter-feeding]] sponges. The cave-dwelling predators capture crustaceans under {{convert|1|mm|in|abbr=on}} long by entangling them with fine threads, digest them by enveloping them with further threads over the course of a few days, and then return to their normal shape; there is no evidence that they use [[venom]].<ref name="Vacelet_1995"/>

Most known carnivorous sponges have completely lost the water flow system and [[choanocyte]]s. However, the [[genus]] ''[[Chondrocladia]]'' uses a highly modified water flow system to inflate balloon-like structures that are used for capturing prey.<ref name="Vacelet_2008"/><ref name="Vacele_2008">{{cite journal |last1= Vacelet |first1=J. |last2=Kelly |first2=Michelle |author-link2=Michelle Kelly (marine scientist) |title=New species from the deep Pacific suggest that carnivorous sponges date back to the Early Jurassic|journal=Nature Precedings|year=2008|doi= 10.1038/npre.2008.2327.1|doi-access=free}}</ref>

=== Endosymbionts ===

Freshwater sponges often host [[green algae]] as [[endosymbiont]]s within [[archaeocyte]]s and other cells and benefit from nutrients produced by the algae. Many marine species host other [[photosynthesis|photosynthesizing]] organisms, most commonly [[cyanobacteria]] but in some cases [[dinoflagellate]]s. Symbiotic cyanobacteria may form a third of the total mass of living tissue in some sponges, and some sponges gain 48% to 80% of their energy supply from these micro-organisms.<ref name="Ruppert_2004"/> In 2008, a [[University of Stuttgart]] team reported that spicules made of [[silica]] conduct light into the [[mesohyl]], where the photosynthesizing endosymbionts live.<ref>{{cite journal |last1=Brümmer |first1=Franz |last2=Pfannkuchen |first2=Martin |last3=Baltz |first3=Alexander |last4=Hauser |first4=Thomas |last5=Thiel |first5=Vera |title=Light inside sponges |journal=[[Journal of Experimental Marine Biology and Ecology]] |volume=367 |issue=2 |pages=61–64 |doi=10.1016/j.jembe.2008.06.036 |year=2008|bibcode=2008JEMBE.367...61B }}
* {{cite news |last=Walker |first=Matt |date=10 November 2008 |title=Nature's 'fibre optics' experts |work=BBC News |url=http://news.bbc.co.uk/2/hi/science/nature/7720836.stm |access-date=11 November 2008 |archive-date=17 December 2008 |archive-url=https://web.archive.org/web/20081217045607/http://news.bbc.co.uk/2/hi/science/nature/7720836.stm |url-status=live }}</ref> Sponges that host photosynthesizing organisms are most common in waters with relatively poor supplies of food particles and often have leafy shapes that maximize the amount of sunlight they collect.<ref name="Bergquist_1998"/>

A recently discovered carnivorous sponge that lives near [[hydrothermal vent]]s hosts [[Methanotrophic|methane-eating]] bacteria and digests some of them.<ref name="Bergquist_1998"/>

=== "Immune" system ===

Sponges do not have the complex [[immune system]]s of most other animals. However, they reject [[Medical grafting|grafts]] from other species but accept them from other members of their own species. In a few marine species, gray cells play the leading role in rejection of foreign material. When invaded, they produce a chemical that stops movement of other cells in the affected area, thus preventing the intruder from using the sponge's internal transport systems. If the intrusion persists, the grey cells concentrate in the area and release toxins that kill all cells in the area. The "immune" system can stay in this activated state for up to three weeks.<ref name="Bergquist_1998"/>

=== Reproduction ===

==== Asexual ====

[[File:Spongilla lacustris.jpg|thumb|right|The freshwater sponge ''[[Spongilla lacustris]]'']]

Sponges have three [[asexual reproduction|asexual]] methods of reproduction: after fragmentation, by [[budding]], and by producing [[gemmule]]s. Fragments of sponges may be detached by currents or waves. They use the mobility of their [[pinacocyte]]s and [[choanocyte]]s and reshaping of the [[mesohyl]] to re-attach themselves to a suitable surface and then rebuild themselves as small but functional sponges over the course of several days. The same capabilities enable sponges that have been squeezed through a fine cloth to regenerate.<ref name="Ruppert_2004"/>{{rp|239}} A sponge fragment can only regenerate if it contains both [[collencyte]]s to produce [[mesohyl]] and [[archeocyte]]s to produce all the other cell types.<ref name="Bergquist_2001"/> A very few species reproduce by budding.<ref name="Ruppert_2004"/>{{rp|90–94}}

Gemmules are "survival pods" which a few marine sponges and many freshwater species produce by the thousands when dying and which some, mainly freshwater species, regularly produce in autumn. [[Spongocyte]]s make gemmules by wrapping shells of spongin, often reinforced with spicules, round clusters of [[archeocyte]]s that are full of nutrients.<ref name="Ruppert_2004"/>{{rp|87–88}} Freshwater gemmules may also include photosynthesizing symbionts.<ref name="Smith_2001">{{cite book|author1=Smith, D. G. |author2=Pennak, R. W. |title=Pennak's Freshwater Invertebrates of the United States: Porifera to Crustacea |publisher=[[John Wiley and Sons]]|year=2001 |isbn=978-0-471-35837-4 |pages=47–50 |edition=4 |url={{google books|plainurl=y|id=GqIctb8IqPoC|page=48}}}}</ref> The gemmules then become dormant, and in this state can survive cold, drying out, lack of oxygen and extreme variations in [[salinity]].<ref name="Ruppert_2004"/> Freshwater gemmules often do not revive until the temperature drops, stays cold for a few months and then reaches a near-"normal" level.<ref name="Smith_2001"/> When a gemmule germinates, the archeocytes round the outside of the cluster transform into [[pinacocyte]]s, a membrane over a pore in the shell bursts, the cluster of cells slowly emerges, and most of the remaining archeocytes transform into other cell types needed to make a functioning sponge. Gemmules from the same species but different individuals can join forces to form one sponge.<ref name="Ruppert_2004"/>{{rp|89–90}} Some gemmules are retained within the parent sponge, and in spring it can be difficult to tell whether an old sponge has revived or been "recolonized" by its own gemmules.<ref name="Smith_2001"/>

==== Sexual ====

Most sponges are [[hermaphrodite]]s (function as both sexes simultaneously), although sponges have no [[gonad]]s (reproductive organs). Sperm are produced by [[choanocyte]]s or entire choanocyte chambers that sink into the [[mesohyl]] and form spermatic [[cyst]]s while eggs are formed by transformation of [[archeocyte]]s, or of choanocytes in some species. Each egg generally acquires a [[yolk]] by consuming "nurse cells". During spawning, sperm burst out of their cysts and are expelled via the [[osculum]]. If they contact another sponge of the same species, the water flow carries them to choanocytes that engulf them but, instead of digesting them, metamorphose to an [[ameboid]] form and carry the sperm through the mesohyl to eggs, which in most cases engulf the carrier and its cargo.<ref name="Ruppert_2004"/>{{rp|77}}

A few species release fertilized eggs into the water, but most retain the eggs until they hatch. By retaining the eggs, the parents can transfer symbiotic microorganisms directly to their offspring through [[vertical transmission]], while the species who release their eggs into the water has to acquire symbionts horizontally (a combination of both is probably most common, where larvae with vertically transmitted symbionts also acquire others horizontally).<ref>{{cite journal |last1=Díez-Vives |first1=Cristina |last2=Koutsouveli |first2=Vasiliki |last3=Conejero |first3=Maria |last4=Riesgo |first4=Ana |title=Global patterns in symbiont selection and transmission strategies in sponges |journal=Frontiers in Ecology and Evolution |volume=10 |date=26 October 2022 |issn=2296-701X |doi=10.3389/fevo.2022.1015592 |doi-access=free}}</ref><ref>{{cite journal |last1=Carrier |first1=Tyler J. |last2=Maldonado |first2=Manuel |last3=Schmittmann |first3=Lara |last4=Pita |first4=Lucía |last5=Bosch |first5=Thomas C. G. |last6=Hentschel |first6=Ute |title=Symbiont transmission in marine sponges: reproduction, development, and metamorphosis |journal=BMC Biology |volume=20 |issue=1 |pages=100 |date=May 2022 |pmid=35524305 |pmc=9077847 |doi=10.1186/s12915-022-01291-6 |doi-access=free }}</ref> There are four types of larvae, but all are lecithotrophic (non-feeding) balls of cells with an outer layer of cells whose [[flagella]] or [[cilia]] enable the larvae to move. After swimming for a few days the larvae sink and crawl until they find a place to settle. Most of the cells transform into archeocytes and then into the types appropriate for their locations in a miniature adult sponge.<ref name="Ruppert_2004"/>{{rp|77}}<ref>{{cite journal |last1=Riesgo |first1=Ana |last2=Taboada |first2=Sergio |last3=Sánchez-Vila |first3=Laura |last4=Solà |first4=Joan |last5=Bertran |first5=Andrea |last6=Avila |first6=Conxita |title=Some Like It Fat: Comparative Ultrastructure of the Embryo in Two Demosponges of the Genus Mycale (Order Poecilosclerida) from Antarctica and the Caribbean |journal=PLOS ONE |volume=10 |issue=3 |date=18 March 2015 |issn=1932-6203 |pmid=25785444 |pmc=4365022 |doi=10.1371/journal.pone.0118805 |doi-access=free |page=e0118805|bibcode=2015PLoSO..1018805R }}</ref>

[[Glass sponge]] embryos start by dividing into separate cells, but once 32&nbsp;cells have formed they rapidly transform into larvae that externally are [[ovoid]] with a band of [[cilia]] round the middle that they use for movement, but internally have the typical glass sponge structure of spicules with a cobweb-like main [[syncitium]] draped around and between them and [[choanosyncytia]] with multiple collar bodies in the center. The larvae then leave their parents' bodies.<ref>{{cite journal |last=Leys |first=S. P. |title=Embryogenesis in the glass sponge Oopsacas minuta: Formation of syncytia by fusion of blastomeres |journal=Integrative and Comparative Biology |volume=46 |issue=2 |date=16 February 2006 |issn=1540-7063 |doi=10.1093/icb/icj016 |pages=104–117|pmid=21672727 }}</ref>

===Meiosis===

The cytological progression of porifera [[oogenesis]] and [[spermatogenesis]] ([[gametogenesis]]) is very similar to that of other metazoa.<ref name="Koutsouveli_2020">{{cite journal |last1=Koutsouveli |first1=Vasiliki |last2=Cárdenas |first2=Paco |last3=Santodomingo |first3=Nadiezhda |last4=Marina |first4=Anabel |last5=Morato |first5=Esperanza |last6=Rapp |first6=Hans Tore |last7=Riesgo |first7=Ana |title=The Molecular Machinery of Gametogenesis in Geodia Demosponges (Porifera): Evolutionary Origins of a Conserved Toolkit across Animals |journal=Molecular Biology and Evolution |volume=37 |issue=12 |date=16 December 2020 |issn=0737-4038 |pmid=32929503 |pmc=7743902 |doi=10.1093/molbev/msaa183 |pages=3485–3506}}</ref> Most of the genes from the classic set of [[meiosis|meiotic]] genes, including genes for DNA recombination and double-strand break repair, that are conserved in [[eukaryote]]s are expressed in the sponges (e.g. ''[[Geodia hentscheli]]'' and ''Geodia phlegraei'').<ref name="Koutsouveli_2020"/> Since porifera are considered to be the earliest divergent animals, these findings indicate that the basic toolkit of meiosis including capabilities for recombination and DNA repair were present early in eukaryote evolution.<ref name="Koutsouveli_2020"/>

==== Life cycle ====
[[File:Bathymetrical range of selected sponge species.jpg|thumb|upright=1.5|right|Bathymetrical range of some sponge species.<ref>{{cite journal |last=Łukowiak |first=M. |title=Utilizing sponge spicules in taxonomic, ecological and environmental reconstructions: a review |journal=PeerJ |volume=8 |pages=e10601 |date=18 December 2020 |pmid=33384908 |pmc=7751429 |doi=10.7717/peerj.10601 |doi-access=free }}</ref> Demosponge ''[[Samus anonymus]]'' (up to 50&nbsp;m), [[hexactinellid]] ''Scleroplegma lanterna'' (~100–600&nbsp;m), hexactinellid ''Aulocalyx irregularis'' (~550–915&nbsp;m), lithistid demosponge ''Neoaulaxinia persicum'' (~500–1700&nbsp;m)]]

Sponges in [[temperate]] regions live for at most a few years, but some [[Tropics|tropical]] species and perhaps some deep-ocean ones may live for 200&nbsp;years or more. Some calcified [[demosponge]]s grow by only {{convert|0.2|mm|in|abbr=on}} per year and, if that rate is constant, specimens {{convert|1|m|ft|abbr=on}} wide must be about 5,000&nbsp;years old. Some sponges start sexual reproduction when only a few weeks old, while others wait until they are several years old.<ref name="Ruppert_2004"/>

=== Coordination of activities ===

Adult sponges lack [[neuron]]s or any other kind of [[nervous tissue]]. However, most species have the ability to perform movements that are coordinated all over their bodies, mainly contractions of the [[pinacocyte]]s, squeezing the water channels and thus expelling excess sediment and other substances that may cause blockages. Some species can contract the [[osculum]] independently of the rest of the body. Sponges may also contract in order to reduce the area that is vulnerable to attack by predators. In cases where two sponges are fused, for example if there is a large but still unseparated bud, these contraction waves slowly become coordinated in both of the "[[Siamese twins]]". The coordinating mechanism is unknown, but may involve chemicals similar to [[neurotransmitter]]s.<ref>{{cite journal |last=Nickel |first=M. |title=Kinetics and rhythm of body contractions in the sponge Tethya wilhelma (Porifera: Demospongiae) |journal=The Journal of Experimental Biology |volume=207 |issue=Pt 26 |pages=4515–24 |date=December 2004 |pmid=15579547 |doi=10.1242/jeb.01289 |doi-access=free |bibcode=2004JExpB.207.4515N }}</ref> However, [[glass sponge]]s rapidly transmit electrical impulses through all parts of the [[syncytium]], and use this to halt the motion of their [[flagella]] if the incoming water contains toxins or excessive sediment.<ref name="Ruppert_2004"/> [[Myocyte]]s are thought to be responsible for closing the osculum and for transmitting signals between different parts of the body.<ref name="Bergquist_1998"/>

Sponges contain [[gene]]s very similar to those that contain the "recipe" for the post-[[synapse|synaptic]] density, an important signal-receiving structure in the neurons of all other animals. However, in sponges these genes are only activated in "flask cells" that appear only in larvae and may provide some sensory capability while the larvae are swimming. This raises questions about whether flask cells represent the predecessors of true neurons or are evidence that sponges' ancestors had true neurons but lost them as they adapted to a sessile lifestyle.<ref>{{cite journal |last1=Sakarya |first1=Onur |last2=Armstrong |first2=Kathryn A. |last3=Adamska |first3=Maja |last4=Adamski |first4=Marcin |last5=Wang |first5=I-Fan |last6=Tidor |first6=Bruce |last7=Degnan |first7=Bernard M. |last8=Oakley |first8=Todd H. |last9=Kosik |first9=Kenneth S. |title=A Post-Synaptic Scaffold at the Origin of the Animal Kingdom |journal=PLOS ONE |volume=2 |issue=6 |date=6 June 2007 |issn=1932-6203 |pmid=17551586 |pmc=1876816 |doi=10.1371/journal.pone.0000506 |doi-access=free |page=e506|bibcode=2007PLoSO...2..506S }}</ref>
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Sponges have several cell types:
* [[Archaeocytes]] (or [[amoebocytes]]) have many functions; they are [[totipotent]] cells which can transform into [[sclerocytes]], [[spongocytes]], or [[collencytes]]. They also have a role in nutrient transport and sexual reproduction.
* Cells are arranged in a gelatinous non-cellular [[Matrix (biology)|matrix]] called mesohyll
Sponges have three body types: [[asconoid]], [[syconoid]], and [[leuconoid]].
* [[Choanocyte]]s (also known as "collar cells") function as the sponge's [[digestive system]], and are remarkably similar to the [[protist]]an [[choanoflagellate]]s. The collars are composed of many [[Microvillus|microvilli]] and are used to filter particles out of the water. The beating of the choanocytes' [[flagellum|flagella]] creates the sponge's water current.
* [[Collencytes]] secrete [[collagen]].
* [[Myocytes (sponge)|Myocytes]] are modified pinacocytes which control the size of the osculum and pore openings and thus the water flow.
* [[Pinacocytes]] which form the [[pinacoderm]], the outer epidermal layer of cells. This is the closest approach to true tissue in sponges
* [[Porocytes]] are tubular cells that make up the sponge's pores.
* [[Sclerocytes]] secrete [[calcareous]] siliceous spicules which reside in the mesohyl.
* [[Spongocytes]] secrete [[spongin]], [[collagen]]-like fibers which make up the mesohyl.
* [[Sponge spicule|Spicules]] are stiffened rods or spikes made of [[calcium carbonate]] or [[Silicon dioxide|silica]] which are used for structure and [[antipredator adaptation|defense]].
-->

== Ecology ==

=== Habitats ===

{{See also|Sponge ground|Sponge reef}}

[[File:Euplectella aspergillum (cropped).jpg|thumb|''[[Euplectella aspergillum]]'' is a [[deep ocean]] [[glass sponge]], seen here at a depth of {{convert|2,572|m}} off the coast of [[California]]]]

Sponges are worldwide in their distribution, living in a wide range of ocean habitats, from the polar regions to the tropics.<ref name="Bergquist_2001"/> Most live in quiet, clear waters, because sediment stirred up by waves or currents would block their pores, making it difficult for them to feed and breathe.<ref name="Krautter_1998"/> The greatest numbers of sponges are usually found on firm surfaces such as rocks, but some sponges can attach themselves to soft sediment by means of a root-like base.<ref>{{cite journal |last1=Weaver |first1=James C. |last2=Aizenberg |first2=Joanna |last3=Fantner |first3=Georg E. |last4=Kisailus |first4=David |last5=Woesz |first5=Alexander |last6=Allen |first6=Peter |last7=Fields |first7=Kirk |last8=Porter |first8=Michael J. |last9=Zok |first9=Frank W. |last10=Hansma |first10=Paul K. |last11=Fratzl |first11=Peter |last12=Morse |first12=Daniel E. |title=Hierarchical assembly of the siliceous skeletal lattice of the hexactinellid sponge Euplectella aspergillum |journal=Journal of Structural Biology |volume=158 |issue=1 |date=2007 |doi=10.1016/j.jsb.2006.10.027 |pages=93–106|pmid=17175169 }}</ref>

Sponges are more abundant but less diverse in temperate waters than in tropical waters, possibly because organisms that prey on sponges are more abundant in tropical waters.<ref>{{cite journal |last1= Ruzicka |first1=R |last2=Gleason |first2=D.F. |title=Latitudinal variation in spongivorous fishes and the effectiveness of sponge chemical defenses |journal=Oecologia |volume=154 |issue=4 |pages=785–94 |date=January 2008 |pmid=17960425 |doi=10.1007/s00442-007-0874-0 |url=http://www.bio.georgiasouthern.edu/Bio-home/Gleason/Ruzicka&Gleasonfulltext.pdf |archive-url=https://web.archive.org/web/20081006123601/http://www.bio.georgiasouthern.edu/Bio-home/Gleason/Ruzicka%26Gleasonfulltext.pdf |url-status=dead |bibcode=2008Oecol.154..785R |s2cid=1495896 |archive-date=2008-10-06 }}</ref> [[Glass sponge]]s are the most common in polar waters and in the depths of temperate and tropical seas, as their very porous construction enables them to extract food from these resource-poor waters with the minimum of effort. [[Demosponge]]s and [[Calcarea|calcareous sponges]] are abundant and diverse in shallower non-polar waters.<ref>{{cite book |last1=Gage |first1=J.D. |last2=Tyler |first2=P.A. |title=Deep-sea Biology: A Natural History of Organisms at the Deep-Sea Floor|publisher=[[Cambridge University Press]] |pages=91–93 |year=1996|isbn=978-0-521-33665-9|url={{google books |plainurl=y |id=kHZO5igKhsAC}}}}</ref>

The different [[Class (biology)|classes]] of sponge live in different ranges of habitat:
{{Clear}}
:{|class="wikitable"
|-
! [[Class (biology)|Class]] !! Water type<ref name="Bergquist_1998"/> !! Depth<ref name="Bergquist_1998"/> !! Type of surface<ref name="Bergquist_1998"/>
|-
! [[Calcarea]]
|Marine ||less than {{convert|100|m|ft|abbr=on}} ||Hard
|-
! [[Glass sponge]]s
|Marine ||Deep ||Soft or firm [[sediment]]
|-
! [[Demosponge]]s
|Marine, brackish; and about 150 freshwater species<ref name="Ruppert_2004"/> ||Inter-tidal to abyssal;<ref name="Bergquist_1998"/> a carnivorous demosponge has been found at {{convert|8840|m|mi|abbr=on}}<ref name="Vacelet_1995"/> ||Any
|}

=== As primary producers ===

Sponges with [[photosynthesis|photosynthesizing]] [[endosymbiont]]s produce up to three times more [[oxygen]] than they consume, as well as more organic matter than they consume. Such contributions to their habitats' resources are significant along Australia's [[Great Barrier Reef]] but relatively minor in the Caribbean.<ref name="Bergquist_2001"/>

=== Defenses ===

[[File:BoredEncrustedShell.JPG|thumb|right|Holes made by clionaid sponge (producing the trace ''[[Entobia]]'') after the death of a modern bivalve shell of species ''[[Mercenaria mercenaria]]'', from [[North Carolina]]]]

Many sponges shed [[Sponge spicule|spicules]], forming a dense carpet several meters deep that keeps away [[echinoderm]]s which would otherwise prey on the sponges.<ref name="Bergquist_2001"/> They also produce toxins that prevent other sessile organisms such as [[bryozoa]]ns or [[sea squirt]]s from growing on or near them, making sponges very effective competitors for living space. One of many examples includes [[ageliferin]], which has antibacterial action and causes biofilms to dissolve.

A few species, including the [[Caribbean]] fire sponge ''[[Tedania]] ignis'', cause a severe rash in humans who handle them.<ref name="Ruppert_2004"/> Turtles and some fish feed mainly on sponges. It is often said that sponges produce [[chemical defense]]s against such predators.<ref name="Ruppert_2004"/> However, experiments have been unable to establish a relationship between the toxicity of chemicals produced by sponges and how they taste to fish, which would diminish the usefulness of chemical defenses as deterrents. Predation by fish may even help to spread sponges by detaching fragments.<ref name="Bergquist_1998"/> However, some studies have shown fish showing a preference for non-chemically-defended sponges,<ref>{{Cite journal |last1=Dunlap |first1=M. |last2=Pawlik |first2=J. R. |date=1996|title=Video-monitored predation by Caribbean reef fishes on an array of mangrove and reef sponges|journal=Marine Biology|volume=126|issue=1 |pages=117–123|doi=10.1007/bf00571383 |bibcode=1996MarBi.126..117D |s2cid=84799900|issn=0025-3162}}</ref> and another study found that high levels of coral predation did predict the presence of chemically defended species.<ref>{{cite journal |last1=Loh |first1=T. L. |last2=Pawlik |first2=J. R. |title=Chemical defenses and resource trade-offs structure sponge communities on Caribbean coral reefs |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=111 |issue=11 |pages=4151–6 |date=March 2014 |pmid=24567392 |pmc=3964098 |doi=10.1073/pnas.1321626111 |bibcode=2014PNAS..111.4151L |doi-access=free }}</ref>

[[Glass sponge]]s produce no toxic chemicals, and live in very deep water where predators are rare.<ref name="Krautter_1998"/>

=== Predation ===
{{further|Spongivore}}

[[File:Generalised food web for sponge reefs.jpg|thumb|upright=2.2|Generalised food web for sponge reefs<ref name= Archer2020>{{cite journal |last1=Archer |first1=Stephanie K. |last2=Kahn |first2=Amanda S. |last3=Thiess |first3=Mary |last4=Law |first4=Lauren |last5=Leys |first5=Sally P. |last6=Johannessen |first6=Sophia C. |last7=Layman |first7=Craig A. |last8=Burke |first8=Lily |last9=Dunham |first9=Anya |title=Foundation Species Abundance Influences Food Web Topology on Glass Sponge Reefs |journal=Frontiers in Marine Science |publisher=Frontiers Media SA |volume=7 |date=24 September 2020 |issn=2296-7745 |doi=10.3389/fmars.2020.549478|doi-access=free |bibcode=2020FrMaS...749478A }} [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}.</ref>]]

Spongeflies, also known as spongillaflies ([[Neuroptera]], [[Sisyridae]]), are specialist predators of freshwater sponges. The female lays her eggs on vegetation overhanging water. The larvae hatch and drop into the water where they seek out sponges to feed on. They use their elongated mouthparts to pierce the sponge and suck the fluids within. The larvae of some species cling to the surface of the sponge while others take refuge in the sponge's internal cavities. The fully grown larvae leave the water and spin a cocoon in which to pupate.<ref>{{cite book |last=Piper |first=Ross |author-link1=Ross Piper |year=2007 |title=Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals |publisher=[[Greenwood Publishing Group]] |isbn=978-0-313-33922-6 |url-access=registration |url=https://archive.org/details/extraordinaryani0000pipe |page=148}}</ref>

=== Bioerosion ===

The Caribbean chicken-liver sponge ''[[Chondrilla nucula]]'' secretes toxins that kill coral [[polyp (zoology)|polyps]], allowing the sponges to grow over the coral skeletons.<ref name="Ruppert_2004"/> Others, especially in the family [[Clionaidae]], use corrosive substances secreted by their archeocytes to tunnel into rocks, corals and the shells of dead [[mollusk]]s.<ref name="Ruppert_2004"/> Sponges may remove up to {{convert|1|m|ft|abbr=on}} per year from reefs, creating visible notches just below low-tide level.<ref name="Bergquist_2001"/>

=== Diseases ===

Caribbean sponges of the genus ''[[Aplysina]]'' suffer from [[Aplysina red band syndrome]]. This causes ''Aplysina'' to develop one or more rust-colored bands, sometimes with adjacent bands of [[necrosis|necrotic]] tissue. These lesions may completely encircle branches of the sponge. The disease appears to be [[Contagious disease|contagious]] and impacts approximately ten percent of ''A. cauliformis'' on Bahamian reefs.<ref name="Gochfeld_2012">{{cite journal|last=Gochfeld |first=D.J. |display-authors=etal |title=Population Dynamics of a Sponge Disease on Caribbean Reefs |journal=Diving for Science 2012 |editor1=Steller, D. |editor2=Lobel, L. |publisher=Proceedings of the American Academy of Underwater Sciences 31st Symposium |year=2012|url=http://archive.rubicon-foundation.org/10327 |archive-url=https://web.archive.org/web/20150904045439/http://archive.rubicon-foundation.org/xmlui/handle/123456789/10327 |archive-date=2015-09-04 |url-status=usurped}}</ref> The rust-colored bands are caused by a [[cyanobacterium]], but it is unknown whether this organism actually causes the disease.<ref name="Gochfeld_2012"/><ref>{{cite journal |last1=Olson |first1=J.B. |last2=Gochfeld |first2=D.J. |last3=Slattery |first3=M. |title=Aplysina red band syndrome: a new threat to Caribbean sponges |journal=Diseases of Aquatic Organisms |volume=71 |issue=2 |pages=163–8 |date=July 2006 |pmid=16956064 |doi=10.3354/dao071163 |doi-access=free }} {{lay source |template=cite web |last=Clarke |first=M. |date=2006-10-17 |title=New disease threatens sponges |website=Practical Fishkeeping |url=http://www.practicalfishkeeping.co.uk/pfk/pages/item.php?news=1113 |archive-url=https://web.archive.org/web/20070926235654/http://www.practicalfishkeeping.co.uk/pfk/pages/item.php?news=1113 |archive-date=2007-09-26}}</ref>

=== Collaboration with other organisms ===

In addition to hosting photosynthesizing endosymbionts,<ref name="Ruppert_2004"/> sponges are noted for their wide range of collaborations with other organisms. The relatively large encrusting sponge ''[[Lissodendoryx]] colombiensis'' is most common on rocky surfaces, but has extended its range into [[seagrass meadow]]s by letting itself be surrounded or overgrown by seagrass sponges, which are distasteful to the local [[starfish]] and therefore protect ''Lissodendoryx'' against them; in return, the seagrass sponges get higher positions away from the sea-floor sediment.<ref>{{cite journal|last=Wulff |first=J. L. |title=Collaboration among sponge species increases sponge diversity and abundance in a seagrass meadow|journal=[[Marine Ecology Progress Series|Marine Ecology]] |volume=29|issue=2|date=June 2008 |pages=193–204 |doi=10.1111/j.1439-0485.2008.00224.x |bibcode=2008MarEc..29..193W |doi-access=free}}</ref>

[[Shrimp]]s of the genus ''[[Synalpheus]]'' form colonies in sponges, and each shrimp species inhabits a different sponge species, making ''Synalpheus'' one of the most diverse [[crustacea]]n genera. Specifically, [[Synalpheus regalis]] utilizes the sponge not only as a food source, but also as a defense against other shrimp and predators.<ref>{{cite journal |last= Duffy |first=J. E. |year=1996 |title=Species boundaries, specialization, and the radiation of sponge-dwelling alpheid shrimp |journal=[[Biological Journal of the Linnean Society]] |volume=58 |issue=3 |pages=307–324 |doi=10.1111/j.1095-8312.1996.tb01437.x |doi-access=free }}</ref> As many as 16,000 individuals inhabit a single [[loggerhead sponge]], feeding off the larger particles that collect on the sponge as it filters the ocean to feed itself.<ref>{{cite book |last= Murphy |first=R.C. |title= Coral Reefs: Cities Under The Seas |year=2002|isbn=978-0-87850-138-0|publisher=[[The Darwin Press]], Inc. |page=51}}</ref> Other crustaceans such as hermit crabs commonly have a specific species of sponge, ''[[Pseudospongosorites]]'', grow on them as both the sponge and crab occupy gastropod shells until the crab and sponge outgrow the shell, eventually resulting in the crab using the sponge's body as protection instead of the shell until the crab finds a suitable replacement shell.<ref>{{cite journal |last=Sandford |first=F. |title=Population dynamics and epibiont associations of hermit crabs (Crustacea: Decapoda: Paguroidea) on Dog Island, Florida |journal=Memoirs of Museum Victoria |year=2003|volume=60 |issue=1 |pages=45–52 |doi=10.24199/j.mmv.2003.60.6 |s2cid=86167606 |issn=1447-2554 |url=https://museumsvictoria.com.au/media/4034/60_1_sandford.pdf |archive-url=https://web.archive.org/web/20180719145946/https://museumsvictoria.com.au/media/4034/60_1_sandford.pdf |archive-date=2018-07-19 |url-status=live |access-date=2022-01-24 }}</ref>

=== Sponge loop ===
[[File:Sponge loop pathway.png|thumb|upright=1.8|right|Sponge loop hypothesis. Steps of the sponge loop pathway: (1)&nbsp;corals and algae release exudates as [[dissolved organic matter]] (DOM), (2)&nbsp;sponges take up DOM, (3)&nbsp;sponges release detrital [[particulate organic matter]] (POM), (4)&nbsp;sponge detritus (POM) is taken up by sponge-associated and free-living [[detritivore]]s.<ref name="Rix_2018">{{cite journal |last1=Rix |first1=L. |last2=de Goeij |first2=J.M. |last3=van Oevelen |first3=D. |last4=Struck |first4=U. |last5=Al-Horani |first5=F.A. |last6=Wild |first6=C. |last7=Naumann |first7=M.S. |title=Reef sponges facilitate the transfer of coral-derived organic matter to their associated fauna via the sponge loop |journal=Marine Ecology Progress Series |volume=589 |date=23 February 2018 |issn=0171-8630 |doi=10.3354/meps12443 |pages=85–96|bibcode=2018MEPS..589...85R }} [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}</ref><ref name="Rix_2017"/><ref name="pmid24092742">{{cite journal |last1=de Goeij |first1=Jasper M. |last2=van Oevelen |first2=Dick |last3=Vermeij |first3=Mark J. A. |last4=Osinga |first4=Ronald |last5=Middelburg |first5=Jack J. |last6=de Goeij |first6=Anton F. P. M. |last7=Admiraal |first7=Wim |title=Surviving in a Marine Desert: The Sponge Loop Retains Resources Within Coral Reefs |journal=Science |volume=342 |issue=6154 |date=4 October 2013 |issn=0036-8075 |doi=10.1126/science.1241981 |pages=108–110|pmid=24092742 |bibcode=2013Sci...342..108D }}</ref>]]

Most sponges are [[detritivore]]s which filter [[Particulate organic matter|organic debris particles]] and [[Marine microorganisms|microscopic life forms]] from ocean water. In particular, sponges occupy an important role as detritivores in [[coral reef food web]]s by recycling detritus to higher [[trophic level]]s.<ref name="Rix_2018"/>

The hypothesis has been made that coral reef sponges facilitate the transfer of coral-derived organic matter to their associated detritivores via the production of sponge detritus, as shown in the diagram. Several sponge species are able to convert coral-derived DOM into sponge detritus,<ref>Rix L, de Goeij JM, Mueller CE, Struck U and others (2016) "Coral mucus fuels the sponge loop in warm- and coldwater coral reef ecosystems". ''Sci Rep'', '''6''': 18715.</ref><ref name="Rix_2017">{{cite journal |last1=Rix |first1=Laura |last2=de Goeij |first2=Jasper M. |last3=van Oevelen |first3=Dick |last4=Struck |first4=Ulrich |last5=Al-Horani |first5=Fuad A. |last6=Wild |first6=Christian |last7=Naumann |first7=Malik S. |date=March 2017 |title=Differential recycling of coral and algal dissolved organic matter via the sponge loop |journal=Functional Ecology |volume=31 |issue=3 |pages=778−789 |doi=10.1111/1365-2435.12758 |bibcode=2017FuEco..31..778R }}</ref> and transfer organic matter produced by corals further up the reef food web. Corals release organic matter as both dissolved and particulate mucus,<ref>{{cite journal |last= Crossland |first=C.J. |date=July 1987 |title=In situ release of mucus and DOC-lipid from the corals Acropora variabilis and Stylophora pistillata in different light regimes. |journal=Coral Reefs |volume=6 |issue=1 |pages=35−42 |doi=10.1007/BF00302210 |bibcode=1987CorRe...6...35C }}</ref><ref name="Wild_2004">{{cite journal |last1=Wild |first1=Christian |last2=Huettel |first2=Markus |last3=Klueter |first3=Anke |last4=Kremb |first4=Stephan G. |last5=Rasheed |first5=Mohammed Y. M. |last6=Jørgensen |first6=Bo B. |title=Coral mucus functions as an energy carrier and particle trap in the reef ecosystem |journal=Nature |volume=428 |issue=6978 |date=2004 |issn=0028-0836 |doi=10.1038/nature02344 |pages=66–70|pmid=14999280 |bibcode=2004Natur.428...66W }}</ref><ref>{{cite journal |last1=Tanaka |first1=Yasuaki |last2=Miyajima |first2=Toshihiro |last3=Umezawa |first3=Yu |last4=Hayashibara |first4=Takeshi |last5=Ogawa |first5=Hiroshi |last6=Koike |first6=Isao |title=Net release of dissolved organic matter by the scleractinian coral Acropora pulchra |journal=Journal of Experimental Marine Biology and Ecology |volume=377 |issue=2 |date=2009 |doi=10.1016/j.jembe.2009.06.023 |pages=101–106|bibcode=2009JEMBE.377..101T }}</ref><ref>{{cite journal |last1=Naumann |first1=M. S. |last2=Haas |first2=A. |last3=Struck |first3=U. |last4=Mayr |first4=C. |last5=el-Zibdah |first5=M. |last6=Wild |first6=C. |date=September 2010 |title=Organic matter release by dominant hermatypic corals of the Northern Red Sea. |journal=Coral Reefs |volume=29 |issue=3 |pages=649−659 |doi=10.1007/s00338-010-0612-7 |bibcode=2010CorRe..29..649N }}</ref> as well as cellular material such as expelled ''[[Symbiodinium]]''.<ref name="Hoegh-Guldberg_1987">{{cite journal |last1=Hoegh-Guldberg |first1=O. |last2=McCloskey |first2=L. R. |last3=Muscatine |first3=L. |date=April 1987 |title=Expulsion of zooxanthellae by symbiotic cnidarians from the Red Sea. |journal=Coral Reefs |volume=5 |issue=4 |pages=201−204 |doi=10.1007/BF00300964 |bibcode=1987CorRe...5..201H }}</ref><ref name="pmid11147708">{{cite journal |last1=Baghdasarian |first1=G |last2=Muscatine |first2=L |title=Preferential expulsion of dividing algal cells as a mechanism for regulating algal-cnidarian symbiosis |journal=The Biological Bulletin |volume=199 |issue=3 |date=2000 |issn=0006-3185 |doi=10.2307/1543184 |pages=278–286|jstor=1543184 |pmid=11147708 |url=https://www.biodiversitylibrary.org/part/10578 }}</ref><ref name="Rix_2018"/>

Organic matter could be transferred from corals to sponges by all these pathways, but DOM likely makes up the largest fraction, as the majority (56 to 80%) of coral mucus dissolves in the water column,<ref name="Wild_2004"/> and coral loss of fixed carbon due to expulsion of ''Symbiodinium'' is typically negligible (0.01%)<ref name="Hoegh-Guldberg_1987"/> compared with mucus release (up to ~40%).<ref>{{cite journal |last1=Crossland |first1=C. J. |last2=Barnes |first2=D. J. |last3=Borowitzka |first3=M. A. |title=Diurnal lipid and mucus production in the staghorn coral Acropora acuminata |journal=Marine Biology |volume=60 |issue=2–3 |date=1980 |issn=0025-3162 |doi=10.1007/BF00389151 |pages=81–90|bibcode=1980MarBi..60...81C }}</ref><ref name="pmid22442377">{{cite journal |last1=Tremblay |first1=Pascale |last2=Grover |first2=Renaud |last3=Maguer |first3=Jean François |last4=Legendre |first4=Louis |last5=Ferrier-Pagès |first5=Christine |title=Autotrophic carbon budget in coral tissue: a new 13C-based model of photosynthate translocation |journal=Journal of Experimental Biology |volume=215 |issue=8 |date=15 April 2012 |issn=1477-9145 |doi=10.1242/jeb.065201 |pages=1384–1393|pmid=22442377 |bibcode=2012JExpB.215.1384T }}</ref> Coral-derived organic matter could also be indirectly transferred to sponges via bacteria, which can also consume coral mucus.<ref>{{cite journal |last1=Ferrier-Pagès |first1=C |last2=Leclercq |first2=N |last3=Jaubert |first3=J |last4=Pelegrí |first4=Sp |title=Enhancement of pico- and nanoplankton growth by coral exudates |journal=Aquatic Microbial Ecology |volume=21 |date=2000 |issn=0948-3055 |doi=10.3354/ame021203 |pages=203–209}}</ref><ref>{{cite journal |last=Wild |first=C. |display-authors=etal |date=July 2010 |title=Organic matter release by Red Sea coral reef organisms—potential effects on microbial activity and in situ O<sub>2</sub> availability. |journal=Marine Ecology Progress Series |volume=411 |pages=61−71 |doi=10.3354/meps08653 |bibcode=2010MEPS..411...61W }}</ref><ref>{{cite journal |last1=Tanaka |first1=Yasuaki |last2=Ogawa |first2=Hiroshi |last3=Miyajima |first3=Toshihiro |title=Production and bacterial decomposition of dissolved organic matter in a fringing coral reef |journal=Journal of Oceanography |volume=67 |issue=4 |date=2011 |issn=0916-8370 |doi=10.1007/s10872-011-0046-z |pages=427–437|bibcode=2011JOce...67..427T }}</ref><ref name="Rix_2018"/>

=== Sponge microbiome ===
{{main|Sponge microbiomes}}
[[File:The sponge holobiont.webp|thumb|upright=1.8|right|The sponge holobiont as a nested ecosystem. Key functions carried out by the [[Sponge microbiomes|sponge microbiome]] (colored arrows) influence holobiont functioning and, through cascading effects, subsequently influence community structure and ecosystem functioning.<ref name="Pita_2018">{{cite journal |last1=Pita |first1=L. |last2=Rix |first2=L. |last3=Slaby |first3=B. M. |last4=Franke |first4=A. |last5=Hentschel |first5=U. |title=The sponge holobiont in a changing ocean: from microbes to ecosystems |journal=Microbiome |volume=6 |issue=1 |date=2018 |page=46 |issn=2049-2618 |pmid=29523192 |pmc=5845141 |doi=10.1186/s40168-018-0428-1 |doi-access=free}} [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}.</ref>]]

Besides a one to one [[symbiotic relationship]], it is possible for a host to become symbiotic with a [[microbial consortium]], resulting in a diverse [[Sponge microbiomes|sponge microbiome]]. Sponges are able to host a wide range of [[Marine microorganisms|microbial communities]] that can also be very specific. The microbial communities that form a symbiotic relationship with the sponge can amount to as much as 35% of the [[Biomass (ecology)|biomass]] of its host.<ref>{{cite journal |last1=Egan |first1=Suhelen |last2=Thomas |first2=Torsten |title=Editorial for: Microbial symbiosis of marine sessile hosts- diversity and function |journal=Frontiers in Microbiology |volume=6 |date=16 June 2015 |page=585 |issn=1664-302X |pmid=26136729 |pmc=4468920 |doi=10.3389/fmicb.2015.00585 |doi-access=free}}</ref>

The term for this specific symbiotic relationship, where a microbial consortia pairs with a host is called a [[Holobiont|holobiotic relationship]]. The sponge as well as the microbial community associated with it will produce a large range of secondary [[metabolite]]s that help protect it against predators through mechanisms such as [[chemical defense]].<ref name="Webster_2016">{{cite journal |last1=Webster |first1=N.S. |last2=Thomas |first2=T. |title=The Sponge Hologenome |journal=mBio |volume=7 |issue=2 |pages=e00135-16 |date=April 2016 |pmid=27103626 |doi=10.1128/mBio.00135-16 |pmc=4850255 }}</ref> The sponge holobiont is an example of the concept of nested ecosystems. Environmental factors act at multiple scales to alter microbiome, holobiont, community, and ecosystem scale processes. Thus, factors that alter microbiome functioning can lead to changes at the holobiont, community, or even ecosystem level and vice versa, illustrating the necessity of considering multiple scales when evaluating functioning in nested ecosystems.<ref name="Pita_2018" />

Some of these relationships include endosymbionts within bacteriocyte cells, and cyanobacteria or microalgae found below the pinacoderm cell layer where they are able to receive the highest amount of light, used for phototrophy. They can host over 50 different microbial phyla and candidate phyla, including Alphaprotoebacteria, [[Actinomycetota]], [[Chloroflexota]], [[Nitrospirota]], "[[Cyanobacteria]]", the taxa Gamma-, the candidate phylum [[Poribacteria]], and [[Thaumarchaea]].<ref name="Webster_2016"/>

== Systematics ==

=== Taxonomy ===

<!-- [[File:Sponge in papua new guinea.jpg|thumb|A sponge in [[Papua New Guinea]]]] -->
<!-- [[File:Biological classification L Pengo.svg|thumb|right|100px|Levels in the [[Linnean taxonomy]].]] -->


[[Carl Linnaeus]], who classified most kinds of sessile animals as belonging to the order [[Vermes in the 10th edition of Systema Naturae#Zoophyta|Zoophyta]] in the class [[Vermes]], mistakenly identified the genus ''[[Spongia]]'' as plants in the order [[Algae]].<ref name=worms>{{cite web |url=http://www.marinespecies.org/aphia.php?p=sourceget&id=44036 |title=Spongia Linnaeus, 1759 |publisher=[[World Register of Marine Species]] |access-date=18 July 2012 |archive-url=https://web.archive.org/web/20160327183441/http://www.marinespecies.org/aphia.php?p=sourceget&id=44036 |archive-date=27 March 2016 |url-status=live }}</ref>{{Explain |date=May 2024 |reason=Spongia 1st genus dedicated to sea sponges during time Linnaeus studied them? }} For a long time thereafter, sponges were assigned to subkingdom [[Parazoa]] ("beside the animals") separated from the [[Eumetazoa]] which formed the rest of the [[Kingdom (biology)|kingdom]] [[Animalia]].<ref name="Rowland_2001"/>

The phylum Porifera is further divided into [[Class (biology)|classes]] mainly according to the composition of their [[skeleton]]s:<ref name="Hooper_2002"/><ref name="Bergquist_2001"/>
* [[Hexactinellida]] (glass sponges) have silicate spicules, the largest of which have six rays and may be individual or fused.<ref name="Hooper_2002"/> The main components of their bodies are [[syncytia]] in which large numbers of cell share a single external [[Cell membrane|membrane]].<ref name="Bergquist_2001"/>
* [[Calcarea]] have skeletons made of [[calcite]], a form of [[calcium carbonate]], which may form separate spicules or large masses. All the cells have a single nucleus and membrane.<ref name="Bergquist_2001"/>
* Most [[Demospongiae]] have silicate spicules or [[spongin]] fibers or both within their soft tissues. However, a few also have massive external skeletons made of [[aragonite]], another form of calcium carbonate.<ref name="Hooper_2002"/><ref name="Bergquist_2001"/> All the cells have a single nucleus and membrane.<ref name="Bergquist_2001"/>
* [[Archeocyatha]] are known only as fossils from the [[Cambrian]] period.<ref name="Rowland_2001"/>

In the 1970s, sponges with massive calcium carbonate skeletons were assigned to a separate class, [[Sclerospongiae]], otherwise known as "coralline sponges".<ref>{{cite journal |last1=Hartman |first1=W.D. |last2=Goreau |first2=T.F. |year=1970|title=Jamaican coralline sponges: Their morphology, ecology and fossil relatives|journal=Symposium of the Zoological Society of London|volume=25|pages=205–243}} [http://mgg.rsmas.miami.edu/groups/sil/work1.htm (cited by MGG.rsmas.miami.edu).] {{Webarchive|url=https://web.archive.org/web/20180818135926/http://mgg.rsmas.miami.edu/groups/sil/work1.htm |date=2018-08-18 }}</ref> However, in the 1980s, it was found that these were all members of either the Calcarea or the Demospongiae.<ref>{{cite book |last=Vacelet |first=J. |year=1985 |contribution=Coralline sponges and the evolution of the Porifera |pages=1–13 |editor1=Conway Morris, S. |editor2=George, J.D. |editor3=Gibson, R. |editor4=Platt, H.M. |title=The Origins and Relationships of Lower Invertebrates |publisher=[[Oxford University Press]]|isbn=978-0-19-857181-0}}</ref>

So far scientific publications have identified about 9,000 poriferan species,<ref name="Bergquist_2001"/> of which about 400 are glass sponges, about 500 are calcareous species, and the rest are demosponges.<ref name="Ruppert_2004"/> However, some types of habitat, such as vertical rock and cave walls and galleries in rock and coral boulders, have been investigated very little, even in shallow seas, and may harbor many more species.<ref name="Bergquist_2001"/>

=== Classes ===

Sponges were traditionally distributed in three classes: calcareous sponges (Calcarea), glass sponges (Hexactinellida) and demosponges (Demospongiae). However, studies have now shown that the [[Homoscleromorpha]], a group thought to belong to the [[Demospongiae]], has a [[phylogenetics|genetic relationship]] well separated from other sponge classes.<ref name="Bergquist_1978"/>{{rp|153–154}} Therefore, they have recently been recognized as the fourth class of sponges.<ref name="Gazave2010">{{cite journal |last1=Gazave |first1=Eve |last2=Lapébie |first2=Pascal |last3=Renard |first3=Emmanuelle |last4=Vacelet |first4=Jean |last5=Rocher |first5=Caroline |last6=Ereskovsky |first6=Alexander V. |last7=Lavrov |first7=Dennis V. |last8=Borchiellini |first8=Carole |title=Molecular phylogeny restores the supra-generic subdivision of homoscleromorph sponges (Porifera, Homoscleromorpha) |journal=PLOS ONE |volume=5 |issue=12 |pages=e14290 |date=December 2010 |pmid=21179486 |pmc=3001884 |doi=10.1371/journal.pone.0014290 |bibcode=2010PLoSO...514290G |doi-access=free }}</ref><ref name="Gazave_2012">{{cite journal |last1=Gazave |first1=Eve |last2=Lapébie |first2=Pascal |last3=Ereskovsky |first3=Alexander V. |last4=Vacelet |first4=Jean |last5=Renard |first5=Emmanuelle |last6=Cárdenas |first6=Paco |last7=Borchiellini |first7=Carole |date=May 2012 |title=No longer Demospongiae: Homoscleromorpha formal nomination as a fourth class of Porifera |url=https://hal.archives-ouvertes.fr/hal-01456632/file/Gazave%20et_2012-%20class.pdf |journal=Hydrobiologia |volume=687 |issue=1 |pages=3–10 |doi=10.1007/s10750-011-0842-x |bibcode=2012HyBio.687....3G |s2cid=14468684 |access-date=2019-08-01 |archive-date=2019-08-01 |archive-url=https://web.archive.org/web/20190801192211/https://hal.archives-ouvertes.fr/hal-01456632/file/Gazave%2520et_2012-%2520class.pdf |url-status=live }}</ref>

<!-- [[File:Sponge in papua new guinea.jpg|thumb|A sponge in [[Papua New Guinea]]]] -->
Sponges are divided into [[Class (biology)|classes]] mainly according to the composition of their [[skeleton]]s:<ref name="Bergquist_1998"/> These are arranged in evolutionary order as shown below in ascending order of their evolution from top to bottom:

:{|class="wikitable"
! [[Class (biology)|Class]] !! Type of cells<ref name="Bergquist_1998">{{cite book |last=Bergquist |first=P.R. |year= 1998 |chapter=Porifera |pages=10–27 |editor=Anderson, D.T. |title=Invertebrate Zoology |publisher=Oxford University Press |isbn=978-0-19-551368-4}}</ref> !! [[Sponge spicule|Spicules]]<ref name="Bergquist_1998"/> !! [[Spongin]] fibers<ref name="Bergquist_1998"/> !! Massive exoskeleton<ref name="Bergquist_2001"/> !! Body form<ref name="Bergquist_1998"/>
|-
! [[Hexactinellida]]
|Always mostly [[syncytia]] ||[[Silica]]<br/>Individual or fused ||Never ||Never ||Leuconoid
|-
! [[Demospongiae]]
|Single nucleus, single external membrane ||Silica ||In many species ||In some species<br />Made of [[aragonite]], if present<ref name="Hooper_2002"/><ref name="Bergquist_2001"/>||Leuconoid
|-
! [[Calcarea]]
|Single nucleus, single external membrane||[[Calcite]]<br/>individual or large masses ||Never ||Common<br/>Made of calcite, if present||Asconoid, syconoid, leuconoid or solenoid<ref name="Cavalcanti_2012">{{cite journal |last1=Cavalcanti |first1=F.F. |last2=Klautau |first2=M. |year=2011 |title=Solenoid: a new aquiferous system to Porifera |journal=Zoomorphology |volume=130 |issue=4 |pages=255–260 |doi=10.1007/s00435-011-0139-7 |s2cid=21745242 }}</ref>
|-
! [[Homoscleromorpha]]
|Single nucleus, single external membrane||Silica ||In many species ||Never ||Sylleibid or leuconoid
|}

=== Phylogeny ===

The phylogeny of sponges has been debated heavily since the advent of [[phylogenetics]]. Originally thought to be the most basal animal phylum, there is now considerable evidence that [[Ctenophora]] may hold that title instead.<ref>{{cite book |last1=Giribet |first1=Gonzalo |last2=Edgecombe |first2=Gregory |title=The Invertebrate Tree of Life |date=3 March 2020 |publisher=Princeton University Press}}</ref><ref>{{cite journal |author1=Schultz, Darrin |display-authors=et al. |title=Ancient gene linkages support ctenophores as sister to other animals |journal=Nature |date=17 May 2023 |volume=618 |issue=7963 |pages=110–117 |doi=10.1038/s41586-023-05936-6|pmid=37198475 |pmc=10232365 |bibcode=2023Natur.618..110S }}</ref> Additionally, the [[monophyly]] of the phylum is now under question. Several studies have concluded that [[Eumetazoa|all other animals]] emerged from within the sponges, and usually recover that the [[calcareous sponge]]s and [[Homoscleromorpha]] are closer to other animals than to [[demosponge]]s.<ref name="Sperling09">{{cite journal |last1=Sperling |first1=Erik |last2=Peterson |first2=Kevin |last3=Pisani |first3=David |title=Phylogenetic-Signal Dissection of Nuclear Housekeeping Genes Supports the Paraphyly of Sponges and the Monophyly of Eumetazoa |journal=Oxford Academic |date=October 2009 |volume=26 |issue=10 |pages=2261–2274 |doi=10.1093/molbev/msp148 |pmid=19597161 |url=https://academic.oup.com/mbe/article/26/10/2261/1109936?searchresult=1}}</ref><ref>{{cite journal |last1=Borchiellini |title=Sponge paraphyly and the origin of Metazoa |journal=Oxford Academic |date=1 January 2001 |volume=14 |issue=1 |pages=171–179 |doi=10.1046/j.1420-9101.2001.00244.x |pmid=29280585 |url=https://academic.oup.com/jeb/article/14/1/171/7323199?searchresult=1}}</ref> The internal relationships of Porifera have proven to be less uncertain. A close relationship of Homoscleromorpha and Calcarea has been recovered in nearly all studies, whether or not they support sponge or eumetazoan monophyly.<ref name="Sperling09"></ref><ref name="Feuda_2017"></ref><ref name="Gazave_2012"></ref><ref name="Gazave2010"></ref> The position of [[glass sponge]]s is also fairly certain, with a majority of studies recovering them as the sister of the demosponges.<ref name="Gazave2010"></ref><ref name="Feuda_2017"></ref><ref name="Sperling09"></ref> Thus, the uncertainty at the base of the animal family tree is probably best represented by the below cladogram.

{{clade
|label1=Animalia
|1={{clade
   |label1=
   |1={{clade
      |label1=
      |1='''[[Hexactinellid]]a''' [[File:Glass-sponge, Euplectella aspergillum.jpg|70px]]
      |2='''[[Demospongiae]]''' [[File:Callyspongiatransparent.png||50px]]
      }}
   |2={{clade
      |label1=
      |1='''[[Calcarea]]''' [[File:Clathrina clathrus.jpg|55px]]
      |2='''[[Homoscleromorpha]]''' [[File:Oscarella lobularis - Schmidt, 1862.jpg|55px]]
      }}
   |3=[[Ctenophora]] [[File:Mnemiopsis leidyi 247259012.png|60px]]
   |4=[[ParaHoxozoa]] [[File:European wasp white bg.jpg|60px]]
   }}
}}

== Evolutionary history ==

=== Fossil record ===
{{see also|Huainan biota}}

[[File:Raphidonema faringdonense 070715a.jpg|thumb|left|''[[Raphidonema (sponge)|Raphidonema faringdonense]]'', a fossil sponge from the [[Cretaceous]] of England]]
{{Annotated image |float=right|caption=[[Archaeocyathid]] structure|image=Archaeocyatha.png|width=150|image-width=150|height=235|image-top=-5|annotations=
{{Annotation|4|11|'''1'''}}
{{Annotation|9|60|'''2'''}}
{{Annotation|17|87|'''3'''}}
{{Annotation|27|124|'''4'''}}
{{Annotation|141|14|'''5'''}}
{{Annotation|139|64|'''6'''}}
{{Annotation|117|124|'''7'''}}
{{Annotation|2|175|'''1''':&nbsp;Gap&nbsp; '''2''':&nbsp;Central&nbsp;cavity&nbsp; '''3'''&nbsp;Internal wall&nbsp; '''4''':&nbsp;Pore (''all'' walls have pores)&nbsp; '''5'''&nbsp;Septum&nbsp; '''6'''&nbsp;Outer wall&nbsp; '''7'''&nbsp;Holdfast}}
}}

[[File:Nevadacoelia wistae.jpg|left|thumb|''[[Nevadacoelia|Nevadacoelia wistae]]'', a fossil [[Anthaspidellidae|anthaspidellid]] [[demosponge]] from the early [[Ordovician]] of [[Nevada]] ]]

Although [[molecular clock]]s and [[biomarker]]s suggest sponges existed well before the [[Cambrian explosion]] of life, [[silica]] spicules like those of demosponges are absent from the fossil record until the Cambrian.<ref>{{cite journal |last1=Sperling |first1=E. A. |last2=Robinson |first2=J. M. |last3=Pisani |first3=D. |last4=Peterson |first4=K. J. |date=January 2010 |title=Where's the glass? Biomarkers, molecular clocks, and microRNAs suggest a 200&nbsp;Myr missing Precambrian fossil record of siliceous sponge spicules |journal=Geobiology |volume=8 |issue=1 |pages=24–36 |pmid=19929965 |doi=10.1111/j.1472-4669.2009.00225.x |bibcode=2010Gbio....8...24S |s2cid=41195363 }}</ref> An unsubstantiated 2002 report exists of spicules in rocks dated around {{ma|750}}.<ref>{{cite book|last1= Reitner |first1=J |last2=Wörheide |first2=G. |contribution=Non-lithistid fossil Demospongiae – origins of their palaeobiodiversity and highlights in history of preservation |editor1=Hooper, J.N. |editor2=Van Soest, R.W. |year=2002 |title=Systema Porifera: A Guide to the Classification of Sponges |publisher=Kluwer Academic Plenum |location=New York, NY |url=http://webdoc.sub.gwdg.de/pub/geo/geobiologie/2005/reitner/2002-porifera.pdf |archive-url=https://web.archive.org/web/20081216220745/http://webdoc.sub.gwdg.de/pub/geo/geobiologie/2005/reitner/2002-porifera.pdf |archive-date=2008-12-16 |url-status=live |access-date=November 4, 2008}}</ref> Well-preserved [[fossil]] sponges from about {{ma|580}} in the [[Ediacaran]] period have been found in the [[Doushantuo Formation]].<ref>{{cite journal|last1=Li|first1=Chia-Wei|last2=Chen|first2=Jun-Yuan|last3=Hua|first3=Tzu-En|title=Precambrian sponges with cellular structures|journal=Science|date=February 1998|volume=279|issue=5352|pages=879–882|doi=10.1126/science.279.5352.879|pmid=9452391|bibcode=1998Sci...279..879L}}</ref> These fossils, which include: spicules; [[pinacocyte]]s; [[porocyte]]s; [[archeocyte]]s; [[sclerocyte]]s; and the internal cavity, have been classified as demosponges. The Ediacaran record of sponges also contains two other genera: the stem-hexactinellid ''[[Helicolocellus]]'' from the [[Dengying Formation]]<ref>{{cite journal |last1=Wang |first1=Xiaopeng |last2=Liu |first2=Alexander G. |last3=Chen |first3=Zhe |last4=Wu |first4=Chengxi |last5=Liu |first5=Yarong |last6=Wan |first6=Bin |last7=Pang |first7=Ke |last8=Zhou |first8=Chuanming |last9=Yuan |first9=Xunlai |last10=Xiao |first10=Shuhai |title=A late-Ediacaran crown-group sponge animal |journal=Nature |date=27 June 2024 |volume=630 |issue=8018 |pages=905–911 |doi=10.1038/s41586-024-07520-y|pmid=38839967 |bibcode=2024Natur.630..905W }}</ref> and the possible stem-archaeocyathan ''[[Arimasia]]'' from the [[Nama Group]].<ref name=arimasia>{{cite journal |last1=Runnegar |first1=Bruce |last2=Gehling |first2=James G. |last3=Jensen |first3=Sören |last4=Saltzman |first4=Matthew R. |title=Ediacaran paleobiology and biostratigraphy of the Nama Group, Namibia, with emphasis on the erniettomorphs, tubular and trace fossils, and a new sponge, Arimasia germsi n. gen. n. sp. |journal=Journal of Paleontology |date=October 2024 |volume=98 |issue=S94 |pages=1–59 |doi=10.1017/jpa.2023.81|bibcode=2024JPal...98S...1R }}</ref> These genera are both from the "Nama assemblage" of Ediacaran biota, although whether this is due to a genuine lack beforehand or preservational bias is uncertain. Fossils of [[glass sponge]]s have been found from around {{ma|540}} in rocks in Australia, China, and Mongolia.<ref name="Müller_2007">{{cite journal |last=Müller |first=W. E. G. |author2=Jinhe Li |last3=Schröder |first3=H. C. |author4=Li Qiao |author5=Xiaohong Wang |year=2007 |title=The unique skeleton of siliceous sponges (Porifera; Hexactinellida and Demospongiae) that evolved first from the Urmetazoa during the Proterozoic: a review |journal=Biogeosciences |volume=4 |issue=2 |pages=219–232 |bibcode=2007BGeo....4..219M |doi=10.5194/bg-4-219-2007 |doi-access=free }}</ref> Early Cambrian sponges from Mexico belonging to the genus ''Kiwetinokia'' show evidence of fusion of several smaller spicules to form a single large spicule.<ref>{{cite journal |last= McMenamin |first=M.A. |year=2008 |title=Early Cambrian sponge spicules from the Cerro Clemente and Cerro Rajón, Sonora, México |journal=[[Geologica Acta]] |volume=6 |issue=4 |pages=363–367 }}</ref> [[Calcium carbonate]] spicules of [[Calcarea|calcareous sponges]] have been found in Early Cambrian rocks from about {{ma|530|523}} in Australia. Other probable demosponges have been found in the Early [[Cambrian]] [[Chengjiang fauna]], from {{ma|525|520}}.<ref name="Li_1998">{{cite journal |last1=Li |first1=Chia-Wei |last2=Chen |first2=Jun-Yuan |last3=Hua |first3=Tzu-En |date=February 1998 |title=Precambrian sponges with cellular structures |journal=Science |volume=279 |issue=5352 |pages=879–82 |pmid=9452391 |doi=10.1126/science.279.5352.879 |bibcode=1998Sci...279..879L |s2cid=38837724 }}</ref> Fossils found in the Canadian Northwest Territories dating to {{ma|890}} may be sponges; if this finding is confirmed, it suggests the first animals appeared before the [[Neoproterozoic_oxygenation_event|Neoproterozoic oxygenation event]].<ref name="Turner_2021">{{cite journal |last=Turner |first=E.C. |title=Possible poriferan body fossils in early Neoproterozoic microbial reefs |journal=Nature |volume=596 |issue=7870 |pages=87–91 |date=August 2021 |pmid=34321662 |pmc=8338550 |doi=10.1038/s41586-021-03773-z |doi-access=free |bibcode=2021Natur.596...87T }}</ref>
[[File:Sauerstoffgehalt-1000mj2.png|thumb|left|Oxygen content of the atmosphere over the last billion years. If confirmed, the discovery of fossilized sponges dating to 890&nbsp;million years ago would predate the Neoproterozoic Oxygenation Event.]]

Freshwater sponges appear to be much younger, as the earliest known fossils date from the Mid-[[Eocene]] period about {{ma|48|40}}.<ref name="Müller_2007"/> Although about 90% of modern sponges are [[demosponges]], fossilized remains of this type are less common than those of other types because their skeletons are composed of relatively soft spongin that does not fossilize well.<ref name="Kazmierczak_2004">{{cite web |title=Demospongia |publisher=[[University of California, Berkeley|U.C. Berkeley]] |department=[[University of California Museum of Paleontology]] |place=Berkeley, CA |url=http://www.ucmp.berkeley.edu/porifera/demospongia.html |access-date=2008-11-27 |url-status=live |archive-url=https://web.archive.org/web/20131018230738/http://www.ucmp.berkeley.edu/porifera/demospongia.html |archive-date=October 18, 2013}}</ref>
The earliest sponge symbionts are known from the [[Llandovery epoch|early Silurian]].<ref name="Vinn_2015">{{cite journal |last1=Vinn |first1=Olev |last2=Wilson |first2=Mark A. |last3=Toom |first3=Ursula |last4=Mõtus |first4=Mari-Ann |year=2015 |title=Earliest known rugosan-stromatoporoid symbiosis from the Llandovery of Estonia (Baltica) |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=31 |pages=1–5 |bibcode=2015PPP...431....1V |doi=10.1016/j.palaeo.2015.04.023 |url=https://www.researchgate.net/publication/275657612 |access-date=2015-06-18 |archive-date=2024-04-10 |archive-url=https://web.archive.org/web/20240410181408/https://www.researchgate.net/publication/275657612_Earliest_known_rugosan-stromatoporoid_symbiosis_from_the_Llandovery_of_Estonia_Baltica |url-status=live }}</ref>

A chemical tracer is [[24-Isopropylcholestane|24-isopropyl cholestane]], which is a stable derivative of 24-isopropyl [[cholesterol]], which is said to be produced by [[demosponge]]s but not by [[eumetazoa]]ns ("true animals", i.e. [[cnidaria]]ns and [[bilateria]]ns). Since [[choanoflagellate]]s are thought to be animals' closest single-celled relatives, a team of scientists examined the [[biochemistry]] and [[gene]]s of one [[choanoflagellate]] species. They concluded that this species could not produce 24-isopropyl cholesterol but that investigation of a wider range of choanoflagellates would be necessary in order to prove that the fossil 24-isopropyl cholestane could only have been produced by demosponges.<ref>{{cite journal |last1=Kodner |first1=Robin B. |last2=Summons |first2=Roger E. |last3=Pearson |first3=Ann |last4=King |first4=Nicole |last5=Knoll |first5=Andrew H. |date=July 2008 |title=Sterols in a unicellular relative of the metazoans |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=105 |issue=29 |pages=9897–9902 |pmid=18632573 |pmc=2481317 |doi=10.1073/pnas.0803975105 |bibcode=2008PNAS..105.9897K |doi-access=free }}</ref>
Although a previous publication reported traces of the chemical 24-isopropyl cholestane in ancient rocks dating to {{ma|1800}},<ref>{{cite journal |last1=Nichols |first1=S. |last2=Wörheide |first2=G. |date=April 2005 |title=Sponges: New views of old animals |journal=Integrative and Comparative Biology |volume=45 |issue=2 |pages=333–334 |pmid=21676777 |doi=10.1093/icb/45.2.333 |citeseerx=10.1.1.598.4999 }}</ref> recent research using a much more accurately dated rock series has revealed that these biomarkers only appear before the end of the [[Marinoan glaciation]] approximately {{ma|635}},<ref>{{cite journal |last1=Love |first1=Gordon D. |last2=Grosjean |first2=Emmanuelle |last3=Stalvies |first3=Charlotte |last4=Fike |first4=David A. |last5=Grotzinger |first5=John P. |last6=Bradley |first6=Alexander S. |last7=Kelly |first7=Amy E. |last8=Bhatia |first8=Maya |last9=Meredith |first9=William |last10=Snape |first10=Colin E. |last11=Bowring |first11=Samuel A. |last12=Condon |first12=Daniel J. |last13=Summons |first13=Roger E. |display-authors=6 |date=February 2009 |title=Fossil steroids record the appearance of Demospongiae during the Cryogenian period |journal=Nature |volume=457 |issue=7230 |pages=718–721 |pmid=19194449 |doi=10.1038/nature07673 |bibcode=2009Natur.457..718L |s2cid=4314662 |url=https://authors.library.caltech.edu/14867/2/Love2009p34510.1038nature07673_supp.pdf |access-date=2019-08-01 |archive-url=https://web.archive.org/web/20180724144041/https://authors.library.caltech.edu/14867/2/Love2009p34510.1038nature07673_supp.pdf |archive-date=2018-07-24 |url-status=dead }}</ref> and that "Biomarker analysis has yet to reveal any convincing evidence for ancient sponges pre-dating the first globally extensive Neoproterozoic glacial episode (the Sturtian, ~{{ma|713}} in Oman)". While it has been argued that this 'sponge biomarker' could have originated from marine algae, recent research suggests that the algae's ability to produce this biomarker evolved only in the [[Carboniferous]]; as such, the biomarker remains strongly supportive of the presence of demosponges in the Cryogenian.<ref name="Antcliffe_2013">{{cite journal |author=Antcliffe, J.B. |year=2013 |editor=Stouge, S. |title=Questioning the evidence of organic compounds called sponge biomarkers |journal=Palaeontology |volume=56 |issue=5 |pages=917–925 |doi=10.1111/pala.12030 |doi-access=free |bibcode=2013Palgy..56..917A }}</ref><ref>{{cite journal |author=Gold, D.A. |title=The slow rise of complex life as revealed through biomarker genetics |journal=Emerging Topics in Life Sciences |volume=2 |issue=2 |pages=191–199 |date=September 2018 |pmid=32412622 |doi=10.1042/ETLS20170150 |s2cid=90887224 }}</ref><ref>{{cite journal |last1=Gold |first1=David A. |last2=Grabenstatter |first2=Jonathan |last3=de Mendoza |first3=Alex |last4=Riesgo |first4=Ana |last5=Ruiz-Trillo |first5=Iñaki |last6=Summons |first6=Roger E. |date=March 2016 |title=Sterol and genomic analyses validate the sponge biomarker hypothesis |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=113 |issue=10 |pages=2684–2689 |pmid=26903629 |pmc=4790988 |doi=10.1073/pnas.1512614113 |bibcode=2016PNAS..113.2684G |doi-access=free }}</ref>

[[Archaeocyathid]]s, which some classify as a type of coralline sponge, are very common fossils in rocks from the Early [[Cambrian]] about {{ma|530|520}}, but apparently died out by the end of the Cambrian {{ma|490}}.<ref name="Li_1998"/>
It has been suggested that they were produced by: sponges; [[cnidaria]]ns; [[algae]]; [[foraminifera]]ns; a completely separate [[phylum]] of animals, Archaeocyatha; or even a completely separate [[Kingdom (biology)|kingdom]] of life, labeled Archaeata or Inferibionta. Since the 1990s, archaeocyathids have been regarded as a distinctive group of sponges.<ref name="Rowland_2001">{{cite journal |author1= Rowland, S.M. |author2=Stephens, T. |year=2001 |title=Archaeocyatha: A history of phylogenetic interpretation |journal=Journal of Paleontology |volume=75 |issue=6 |pages=1065–1078 |jstor=1307076 |doi=10.1666/0022-3360(2001)075<1065:AAHOPI>2.0.CO;2}}</ref>

{{clear left}}
{{Annotated image|float=left|caption=[[Halkieriid]] sclerite structure<ref name="Porter_2008"/> |image=Halkieriid sclerite structure 300.png |width=210 |height=96 |image-width=200 |image-left=0 |image-top=0
|annotations =
{{Annotation|141|44|{{=}} skin}}
{{Annotation|141|64|{{=}} [[aragonite]]}}
{{Annotation|141|84|{{=}} flesh}}
}}
It is difficult to fit [[chancelloriid]]s into classifications of sponges or more complex animals. An analysis in 1996 concluded that they were closely related to sponges on the grounds that the detailed structure of chancellorid sclerites ("armor plates") is similar to that of fibers of spongin, a [[collagen]] [[protein]], in modern keratose (horny) [[demosponge]]s such as ''[[Darwinella (sponge)|Darwinella]]''.<ref>{{cite journal |author1=Butterfield, N.J. |author2=Nicholas, C.J. |year=1996 |title=Burgess Shale-type preservation of both non-mineralizing and "shelly" Cambrian organisms from the Mackenzie Mountains, northwestern Canada |journal=Journal of Paleontology |volume=70 |issue=6 |pages=893–899 |jstor=1306492 |doi=10.1017/S0022336000038579 |bibcode=1996JPal...70..893B |s2cid=133427906 }}</ref> However, another analysis in 2002 concluded that chancelloriids are not sponges and may be intermediate between sponges and more complex animals, among other reasons because their skins were thicker and more tightly connected than those of sponges.<ref name="Janussen_2002">{{cite journal |last1=Janussen |first1=Dorte |last2=Steiner |first2=Michael |last3=Maoyan |first3=Zhu |year=2002 |title=New well-preserved scleritomes of Chancelloridae from the early Cambrian Yuanshan Formation (Chengjiang, China) and the middle Cambrian Wheeler Shale (Utah, USA) and paleobiological implications |journal=Journal of Paleontology |volume=76 |issue=4 |pages=596–606 |doi=10.1666/0022-3360(2002)076<0596:NWPSOC>2.0.CO;2|bibcode=2002JPal...76..596J |s2cid=129127213 }} free text at {{cite news |last=Janussen |first=D. |year=2002 |title=(full text without images) |journal=[[Journal of Paleontology]] |url=http://findarticles.com/p/articles/mi_qa3790/is_200207/ai_n9134583/pg_1?tag=artBody;col1 |access-date=2008-08-04 |archive-date=December 10, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20081210092130/http://findarticles.com/p/articles/mi_qa3790/is_200207/ai_n9134583/pg_1?tag=artBody%3Bcol1}}</ref> In 2008, a detailed analysis of chancelloriids' sclerites concluded that they were very similar to those of [[halkieriid]]s, mobile [[bilaterian]] animals that looked like [[slug]]s in [[chain mail]] and whose fossils are found in rocks from the very Early Cambrian to the Mid Cambrian. If this is correct, it would create a dilemma, as it is extremely unlikely that totally unrelated organisms could have developed such similar sclerites independently, but the huge difference in the structures of their bodies makes it hard to see how they could be closely related.<ref name="Porter_2008">{{cite journal |last=Porter |first=S.M. |year=2008 |title=Skeletal microstructure indicates Chancelloriids and Halkieriids are closely related |journal=[[Palaeontology (journal)|Palaeontology]] |volume=51 |issue=4 |pages=865–879 |doi=10.1111/j.1475-4983.2008.00792.x |bibcode=2008Palgy..51..865P |doi-access=free}}</ref>

=== Relationships to other animal groups ===

{{cladogram
 |title=Simplified family tree showing [[Calcarea|calcareous sponges]] as closest to more complex animals<ref name="Borchiellini_2001"/>
 |clades={{clade
     |label1=[[Opisthokonta]]
     |1={{clade
       |1=[[Fungi]]
       |2={{clade
        |1=[[Choanoflagellate]]s
        |label2=[[Metazoa]]
        |2={{clade
          |1=[[Glass sponge]]s
          |2={{clade
           |1=[[Demosponge]]s
           |2={{clade
             |1=[[Calcarea|Calcareous sponges]]
             |label2=[[Eumetazoa]]
             |2={{clade
              |1=[[Ctenophora|Comb jellies]]
              |2={{clade
                |1=[[Placozoa]]
                |2={{clade
                 |1=[[Cnidaria]]<br />(jellyfish, etc.)
                 |2=other [[metazoa]]ns
                 }}
                }}
              }}
             }}
           }}
          }}
        }}
       }}
     }}
}}
{{cladogram
 |title=Simplified family tree showing [[Homoscleromorpha]] as closest to more complex animals<ref name="Sperling_2007"/>
 |clades={{clade
     |label1=[[Eukaryotes]]
     |1={{clade
       |1=[[Plant]]s
       |2=[[Fungi]]
       |label3=[[Metazoa]]
       |3={{clade
        |1=Most [[demosponge]]s
        |2={{clade
          |1=[[Calcarea|Calcareous sponges]]
          |2={{clade
           |1=[[Homoscleromorpha]]
           |label2=[[Eumetazoa]]
           |2={{clade
             |1=[[Cnidaria]]<br />(jellyfish, etc.)
             |2=other [[metazoa]]ns
             }}
           }}
          }}
        }}
       }}
     }}
}}
In the 1990s, sponges were widely regarded as a [[monophyletic]] group, all of them having descended from a [[last universal common ancestor|common ancestor]] that was itself a sponge, and as the "sister-group" to all other [[animals|metazoans]] (multi-celled animals), which themselves form a monophyletic group. On the other hand, some 1990s analyses also revived the idea that animals' nearest evolutionary relatives are [[choanoflagellate]]s, single-celled organisms very similar to sponges' [[choanocytes]] – which would imply that most Metazoa evolved from very sponge-like ancestors and therefore that sponges may not be monophyletic, as the same sponge-like ancestors may have given rise both to modern sponges and to non-sponge members of Metazoa.<ref name="Borchiellini_2001">{{cite journal |last1=Borchiellini |first1=C. |last2=Manuel |first2=M. |last3=Alivon |first3=E. |last4=Boury-Esnault |first4=N. |last5=Vacelet |first5=J. |last6=Le Parco |first6=Y. |title=Sponge paraphyly and the origin of Metazoa |journal=Journal of Evolutionary Biology |volume=14 |issue=1 |pages=171–179 |date=January 2001 |pmid=29280585 |doi=10.1046/j.1420-9101.2001.00244.x |doi-access=free }}</ref>

Analyses since 2001 have concluded that [[Eumetazoa]] (more complex than sponges) are more closely related to particular groups of sponges than to other sponge groups. Such conclusions imply that sponges are not monophyletic, because the [[most recent common ancestor|last common ancestor]] of all sponges would also be a direct ancestor of the Eumetazoa, which are not sponges. A study in 2001 based on comparisons of [[ribosome]] [[DNA]] concluded that the most fundamental division within sponges was between [[glass sponge]]s and the rest, and that Eumetazoa are more closely related to [[Calcarea|calcareous sponges]] (those with calcium carbonate spicules) than to other types of sponge.<ref name="Borchiellini_2001"/> In 2007, one analysis based on comparisons of [[RNA]] and another based mainly on comparison of spicules concluded that demosponges and glass sponges are more closely related to each other than either is to the calcareous sponges, which in turn are more closely related to Eumetazoa.<ref name="Müller_2007"/><ref>{{cite journal |last1=Medina |first1=Mónica |last2=Collins |first2=Allen G. |last3=Silberman |first3=Jeffrey D. |last4=Sogin |first4=Mitchell L. |title=Evaluating hypotheses of basal animal phylogeny using complete sequences of large and small subunit rRNA |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=98 |issue=17 |pages=9707–12 |date=August 2001 |pmid=11504944 |pmc=55517 |bibcode=2001PNAS...98.9707M |doi=10.1073/pnas.171316998 |doi-access=free }}</ref>

Other anatomical and biochemical evidence links the Eumetazoa with [[Homoscleromorpha]], a sub-group of demosponges. A comparison in 2007 of [[cell nucleus|nuclear]] [[DNA]], excluding glass sponges and [[Ctenophora|comb jellies]], concluded that:
* [[Homoscleromorpha]] are most closely related to Eumetazoa;
* calcareous sponges are the next closest;
* the other demosponges are evolutionary "aunts" of these groups; and
* the [[chancelloriidae|chancelloriids]], bag-like animals whose fossils are found in [[Cambrian]] rocks, may be sponges.<ref name="Sperling_2007">{{cite journal |last1=Sperling |first1=E. A. |last2=Pisani |first2=D. |last3=Peterson |first3=K. J. |year=2007 |title=Poriferan paraphyly and its implications for Precambrian paleobiology |journal=Journal of the Geological Society of London |volume=286 |issue=1 |pages=355–368 |doi=10.1144/SP286.25 |bibcode=2007GSLSP.286..355S |s2cid=34175521 |url=http://www.dartmouth.edu/~peterson/Sperling,%20Pisani%20and%20Peterson.pdf |url-status=dead |access-date=2008-11-04 |archive-url=https://web.archive.org/web/20090509061759/http://www.dartmouth.edu/~peterson/Sperling,%20Pisani%20and%20Peterson.pdf |archive-date=May 9, 2009}}</ref>
The [[sperm]] of Homoscleromorpha share features with the sperm of Eumetazoa, that sperm of other sponges lack. In both Homoscleromorpha and Eumetazoa layers of cells are bound together by attachment to a carpet-like basal membrane composed mainly of "typ&nbsp;IV" [[collagen]], a form of collagen not found in other sponges – although the [[spongin]] fibers that reinforce the mesohyl of all demosponges is similar to "type&nbsp;IV" collagen.<ref name="Exposito_2002">{{cite journal |last1=Exposito |first1=Jean-Yves |last2=Cluzel |first2=Caroline |last3=Garrone |first3=Robert |last4=Lethias |first4=Claire |title=Evolution of collagens |journal=The Anatomical Record |volume=268 |issue=3 |pages=302–16 |date=November 2002 |pmid=12382326 |doi=10.1002/ar.10162 |doi-access=free }}</ref>

[[File:Bathocyroe fosteri.jpg|thumb|left|A [[ctenophora|comb jelly]] ]]
The analyses described above concluded that sponges are closest to the ancestors of all Metazoa, of all multi-celled animals including both sponges and more complex groups. However, another comparison in 2008 of 150&nbsp;genes in each of 21&nbsp;genera, ranging from fungi to humans but including only two species of sponge, suggested that [[ctenophora|comb jellies]] ([[ctenophora]]) are the most basal lineage of the Metazoa included in the sample.<ref name="Dunn_2008">{{cite journal |last1=Dunn |first1=Casey W. |last2=Hejnol |first2=Andreas |last3=Matus |first3=David Q. |last4=Pang |first4=Kevin |last5=Browne |first5=William E. |last6=Smith |first6=Stephen A. |last7=Seaver |first7=Elaine |last8=Rouse |first8=Greg W. |last9=Obst |first9=Matthias |last10=Edgecombe |first10=Gregory D. |last11=Sørensen |first11=Martin V. |last12=Haddock |first12=Steven H. D. |last13=Schmidt-Rhaesa |first13=Andreas |last14=Okusu |first14=Akiko |last15=Kristensen |first15=Reinhardt Møbjerg |last16=Wheeler |first16=Ward C. |last17=Martindale |first17=Mark Q. |last18=Giribet |first18=Gonzalo |display-authors=6 |title=Broad phylogenomic sampling improves resolution of the animal tree of life |journal=Nature |volume=452 |issue=7188 |pages=745–9 |date=April 2008 |pmid=18322464 |doi=10.1038/nature06614 |bibcode=2008Natur.452..745D |s2cid=4397099 }}</ref><ref name="Hejnol_2009">{{cite journal |last1=Hejnol |first1=Andreas |last2=Obst |first2=Matthias |last3=Stamatakis |first3=Alexandros |last4=Ott |first4=Michael |last5=Rouse |first5=Greg W. |last6=Edgecombe |first6=Gregory D. |last7=Martinez |first7=Pedro |last8=Baguñà |first8=Jaume |last9=Bailly |first9=Xavier |last10=Jondelius |first10=Ulf |last11=Wiens |first11=Matthias |last12=Müller |first12=Werner E. G. |last13=Seaver |first13=Elaine |last14=Wheeler |first14=Ward C. |last15=Martindale |first15=Mark Q. |last16=Giribet |first16=Gonzalo |last17=Dunn |first17=Casey W. |display-authors=6 |title=Assessing the root of bilaterian animals with scalable phylogenomic methods |journal=Proceedings. Biological Sciences |volume=276 |issue=1677 |pages=4261–70 |date=December 2009 |pmid=19759036 |pmc=2817096 |doi=10.1098/rspb.2009.0896 }}</ref><ref name="Ryan_2013">{{cite journal |last1=Ryan |first1=Joseph F. |last2=Pang |first2=Kevin |last3=Schnitzler |first3=Christine E. |last4=Nguyen |first4=Anh-Dao |last5=Moreland |first5=R. Travis |last6=Simmons |first6=David K. |last7=Koch |first7=Bernard J. |last8=Francis |first8=Warren R. |last9=Havlak |first9=Paul |author10=NISC Comparative Sequencing Program |last11=Smith |first11=Stephen A. |last12=Putnam |first12=Nicholas H. |last13=Haddock |first13=Steven H. D. |last14=Dunn |first14=Casey W. |last15=Wolfsberg |first15=Tyra G. |last16=Mullikin |first16=James C. |last17=Martindale |first17=Mark Q. |last18=Baxevanis |first18=Andreas D. |display-authors=6 |title=The genome of the ctenophore Mnemiopsis leidyi and its implications for cell type evolution |journal=Science |volume=342 |issue=6164 |page=1242592 |date=December 2013 |pmid=24337300 |pmc=3920664 |doi=10.1126/science.1242592 }}</ref><ref name="Moroz_2014">{{cite journal |last1=Moroz |first1=Leonid L. |last2=Kocot |first2=Kevin M. |last3=Citarella |first3=Mathew R. |last4=Dosung |first4=Sohn |last5=Norekian |first5=Tigran P. |last6=Povolotskaya |first6=Inna S. |last7=Grigorenko |first7=Anastasia P. |last8=Dailey |first8=Christopher |last9=Berezikov |first9=Eugene |last10=Buckley |first10=Katherine M. |last11=Ptitsyn |first11=Andrey |last12=Reshetov |first12=Denis |last13=Mukherjee |first13=Krishanu |last14=Moroz |first14=Tatiana P. |last15=Bobkova |first15=Yelena |last16=Yu |first16=Fahong |last17=Kapitonov |first17=Vladimir V. |last18=Jurka |first18=Jerzy |last19=Bobkov |first19=Yuri V. |last20=Swore |first20=Joshua J. |last21=Girardo |first21=David O. |last22=Fodor |first22=Alexander |last23=Gusev |first23=Fedor |last24=Sanford |first24=Rachel |last25=Bruders |first25=Rebecca |last26=Kittler |first26=Ellen |last27=Mills |first27=Claudia E. |last28=Rast |first28=Jonathan P. |last29=Derelle |first29=Romain |last30=Solovyev |first30=Victor V. |last31=Kondrashov |first31=Fyodor A. |last32=Swalla |first32=Billie J. |last33=Sweedler |first33=Jonathan V. |last34=Rogaev |first34=Evgeny I. |last35=Halanych |first35=Kenneth M. |last36=Kohn |first36=Andrea B. |display-authors=6 |title=The ctenophore genome and the evolutionary origins of neural systems |journal=Nature |volume=510 |issue=7503 |date=2014 |issn=0028-0836 |pmid=24847885 |pmc=4337882 |doi=10.1038/nature13400 |pages=109–114|bibcode=2014Natur.510..109M }}</ref> If this is correct, either modern comb jellies developed their complex structures independently of other Metazoa, or sponges' ancestors were more complex and all known sponges are drastically simplified forms. The study recommended further analyses using a wider range of sponges and other simple Metazoa such as [[Placozoa]].<ref name="Dunn_2008"/>

However, reanalysis of the data showed that the computer algorithms used for analysis were misled by the presence of specific ctenophore genes that were markedly different from those of other species, leaving sponges as either the sister group to all other animals, or an ancestral paraphyletic grade.<ref>{{cite journal |last1=Pisani |first1=Davide |last2=Pett |first2=Walker |last3=Dohrmann |first3=Martin |last4=Feuda |first4=Roberto |last5=Rota-Stabelli |first5=Omar |last6=Philippe |first6=Hervé |last7=Lartillot |first7=Nicolas |last8=Wörheide |first8=Gert |title=Genomic data do not support comb jellies as the sister group to all other animals |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=112 |issue=50 |pages=15402–15407 |date=December 2015 |pmid=26621703 |pmc=4687580 |doi=10.1073/pnas.1518127112 |doi-access=free |bibcode=2015PNAS..11215402P }}</ref><ref>{{Cite book |title=Spineless: the science of jellyfish and the art of growing a backbone |last= Berwald |first=Juli |publisher=Riverhead Books |year=2017|isbn=9780735211261}}{{page needed|date=October 2018}}</ref> 'Family trees' constructed using a combination of all available data – morphological, developmental and molecular – concluded that the sponges are in fact a monophyletic group, and with the [[cnidarian]]s form the sister group to the bilaterians.<ref name="Schierwater_2009">{{cite journal |last1=Schierwater |first1=Bernd |last2=Eitel |first2=Michael |last3=Jakob |first3=Wolfgang |last4=Osigus |first4=Hans-Jürgen |last5=Hadrys |first5=Heike |last6=Dellaporta |first6=Stephen L. |last7=Kolokotronis |first7=Sergios-Orestis |last8=DeSalle |first8=Rob |title=Concatenated analysis sheds light on early metazoan evolution and fuels a modern "urmetazoon" hypothesis |journal=PLOS Biology |volume=7 |issue=1 |pages=e20 |date=January 2009 |pmid=19175291 |pmc=2631068 |doi=10.1371/journal.pbio.1000020 |doi-access=free }}</ref><ref name="Kapli_2020">{{cite journal |last1= Kapli |first1=P. |last2=Telford |first2=M.J. |title=Topology-dependent asymmetry in systematic errors affects phylogenetic placement of Ctenophora and Xenacoelomorpha |journal=Science Advances |volume=6 |issue=50 |pages=eabc5162 |date=December 2020 |pmid=33310849 |pmc=7732190 |doi=10.1126/sciadv.abc5162 |doi-access=free |bibcode=2020SciA....6.5162K }}</ref>

A very large and internally consistent alignment of 1,719&nbsp;proteins at the metazoan scale, published in 2017, showed that (i)&nbsp;sponges – represented by Homoscleromorpha, Calcarea, Hexactinellida, and Demospongiae – are monophyletic, (ii)&nbsp;sponges are sister-group to all other multicellular animals, (iii)&nbsp;ctenophores emerge as the second-earliest branching animal lineage, and (iv)&nbsp;[[placozoans]] emerge as the third animal lineage, followed by [[Planulozoa|cnidarians sister-group to bilaterians]].<ref name="Simion_2017">{{cite journal |last1=Simion |first1=Paul |last2=Philippe |first2=Hervé |last3=Baurain |first3=Denis |last4=Jager |first4=Muriel |last5=Richter |first5=Daniel J. |last6=Di Franco |first6=Arnaud |last7=Roure |first7=Béatrice |last8=Satoh |first8=Nori |last9=Quéinnec |first9=Éric |last10=Ereskovsky |first10=Alexander |last11=Lapébie |first11=Pascal |last12=Corre |first12=Erwan |last13=Delsuc |first13=Frédéric |last14=King |first14=Nicole |last15=Wörheide |first15=Gert |last16=Manuel |first16=Michaël |display-authors=6 |title=A Large and Consistent Phylogenomic Dataset Supports Sponges as the Sister Group to All Other Animals |journal=Current Biology |volume=27 |issue=7 |pages=958–967 |date=April 2017 |pmid=28318975 |doi=10.1016/j.cub.2017.02.031 |url=https://hal.archives-ouvertes.fr/hal-01681528/file/Simion_etal2017_CurrBiol_proofs.pdf |type=<!-- Submitted manuscript --> |doi-access=free |bibcode=2017CBio...27..958S |access-date=2018-11-04 |archive-date=2020-04-25 |archive-url=https://web.archive.org/web/20200425191351/https://hal.archives-ouvertes.fr/hal-01681528/file/Simion_etal2017_CurrBiol_proofs.pdf |url-status=live }}</ref>

In March&nbsp;2021, scientists from Dublin found additional evidence that sponges are the sister group to all other animals,<ref>{{cite journal |last1= Redmond |first1=A.K. |last2=McLysaght |first2=A. |title=Evidence for sponges as sister to all other animals from partitioned phylogenomics with mixture models and recoding |journal=Nature Communications |volume=12 |issue=1 |pages=1783 |date=March 2021 |pmid=33741994 |pmc=7979703 |doi=10.1038/s41467-021-22074-7 |doi-access=free |bibcode=2021NatCo..12.1783R }}</ref> while in May&nbsp;2023, Schultz et al. found patterns of irreversible change in genome synteny that provide strong evidence that [[ctenophora|ctenophores]] are the sister group to all other animals instead.<ref>{{cite journal |last1=Schultz |first1=Darrin T. |last2=Haddock |first2=Steven H. D. |last3=Bredeson |first3=Jessen V. |last4=Green |first4=Richard E. |last5=Simakov |first5=Oleg |last6=Rokhsar |first6=Daniel S. |title=Ancient gene linkages support ctenophores as sister to other animals |journal=Nature |volume=618 |issue=7963 |pages=110–117 |date=June 2023 |pmid=37198475 |pmc=10232365 |doi=10.1038/s41586-023-05936-6 |bibcode=2023Natur.618..110S }}</ref>

== Notable spongiologists ==
{{div col|colwidth=20em}}
* [[Céline Allewaert]]
* [[Patricia Bergquist]]
* [[James Scott Bowerbank]]
* [[Maurice Burton]]
* [[Henry John Carter]]
* [[Max Walker de Laubenfels]]
* [[Arthur Dendy]]
* [[Édouard Placide Duchassaing de Fontbressin]]
* [[Randolph Kirkpatrick]]
* [[Robert J. Lendlmayer von Lendenfeld]]
* [[Edward Alfred Minchin]]
* [[Giovanni Domenico Nardo]]
* [[Eduard Oscar Schmidt]]
* [[Émile Topsent]]
{{div col end}}

== Use ==

=== By dolphins ===

A report in 1997 described use of sponges [[Tool use by non-human animals|as a tool]] by [[bottlenose dolphins]] in [[Shark Bay]] in Western Australia. A dolphin will attach a marine sponge to its [[rostrum (anatomy)|rostrum]], which is presumably then used to protect it when searching for food in the sandy [[sea floor|sea bottom]].<ref name="Smolker 1997">{{cite journal |last1=Smolker |first1=Rachel |last2=Richards |first2=Andrew |last3=Connor |first3=Richard |last4=Mann |first4=Janet |last5=Berggren |first5=Per |title=Sponge-carrying by Indian Ocean bottlenose dolphins: Possible tool-use by a delphinid |journal=Ethology |year=1997 |volume=103 |pages=454–465 |doi=10.1111/j.1439-0310.1997.tb00160.x |issue=6 |hdl=2027.42/71936 |hdl-access=free}}</ref> The behavior, known as ''sponging'', has only been observed in this bay and is almost exclusively shown by females.<!-- This is the only known case of tool use in [[marine mammal]]s outside of [[sea otter]]s.--> A study in 2005 concluded that mothers teach the behavior to their daughters and that all the sponge users are closely related, suggesting that it is a fairly recent innovation.<ref name="Krutzen_2005">{{cite journal |last1=Krützen |first1=Michael |last2=Mann |first2=Janet |last3=Heithaus |first3=Michael R. |last4=Connor |first4=Richard C. |last5=Bejder |first5=Lars |last6=Sherwin |first6=William B. |title=Cultural transmission of tool use in bottlenose dolphins |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=102 |issue=25 |pages=8939–43 |date=June 2005 |pmid=15947077 |pmc=1157020 |doi=10.1073/pnas.0500232102 |bibcode=2005PNAS..102.8939K |doi-access=free }}</ref>

=== By humans ===

{{Main|Sea sponge aquaculture|Sponge diving}}

==== Skeleton ====

{{Main|Sponge (material)}}

The [[calcium carbonate]] or [[silica]] [[Sponge spicule|spicules]] of most sponge [[genus|genera]] make them too rough for most uses, but two genera, ''[[Hippospongia]]'' and ''[[Spongia]]'', have soft, entirely fibrous skeletons.<ref name="Bergquist_1978"/>{{rp|88}} Early Europeans used soft sponges for many purposes, including padding for helmets, portable drinking utensils and municipal water filters. Until the invention of synthetic sponges, they were used as cleaning tools, applicators for paints and [[ceramic glaze]]s and discreet [[contraceptive]]s. However, by the mid-20th century, overfishing brought both the animals and the industry close to [[extinction]].<ref>{{cite book |last=McClenachan |first=L. |chapter=Social conflict, Over-fishing and Disease in the Florida Sponge Fishery, 1849–1939 |pages=25–27 |title=Oceans Past: Management Insights from the History of Marine Animal Populations |editor1=Starkey, D.J. |editor2=Holm, P. |editor3=Barnard, M. |publisher=[[Earthscan]] |year=2008 |isbn=978-1-84407-527-0 |chapter-url={{google books |plainurl=y |id=cGEeEfFegvEC|page=26}}}}</ref>

Many objects with sponge-like textures are now made of substances not derived from poriferans. Synthetic sponges include personal and household [[Sponge (material)|cleaning tools]], [[breast implant]]s,<ref>{{cite book |last=Jacobson |first=N. |title=Cleavage |publisher=Rutgers University Press|isbn=978-0-8135-2715-4|url={{google books |plainurl=y |id=3ZIw_3Px4AEC|page=62}}|year=2000|page=62}}</ref> and [[contraceptive sponge]]s.<ref name="CBAS">{{Cite journal |title=Sponges |journal=[[Cervical Barrier Advancement Society]] |year=2004 |url=http://www.cervicalbarriers.org/information/sponges.cfm |access-date=2006-09-17 |archive-date=January 14, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20090114062634/http://www.cervicalbarriers.org/information/sponges.cfm }}</ref> Typical materials used are [[cellulose]] foam, [[polyurethane]] foam, and less frequently, [[silicone]] foam.

The [[Exfoliation (cosmetology)#Loofah|luffa]] "sponge", also spelled ''loofah'', which is commonly sold for use in the kitchen or the shower, is not derived from an animal but mainly from the fibrous "skeleton" of the [[Luffa aegyptiaca|sponge gourd]] (''Luffa aegyptiaca'', [[Cucurbitaceae]]).<ref>{{cite journal |last=Porterfield |first=W.M. |title=Loofah — The sponge gourd |journal=[[Economic Botany]] |volume=9 |issue=3 |year=1955 |pages=211–223 |doi=10.1007/BF02859814 |bibcode=1955EcBot...9..211P |s2cid=27313678 }}</ref>

<gallery class=center mode=nolines widths=180 heights=180 title=Human uses of sponges>
File:2008.09-331-196ap Sponge gourd,pd Spice Bazaar@Istanbul,TR mon29sep2008-1315h.jpg|Sponges made of [[Luffa aegyptiaca|sponge gourd]] for sale alongside sponges of animal origin, [[Spice Bazaar, Istanbul]] 
File:SpongesTarponSprings.jpg|Natural sponges in [[Tarpon Springs]], [[Florida]]
</gallery>

==== Medicinal compounds ====

{{further|Sponge isolates}}

[[File:Halichondria and Eribulin.jpg|thumb|upright|''Halichondria'' produces the [[eribulin]] precursor [[halichondrin B]] ]]

Sponges have [[medicine|medicinal]] potential due to the presence in sponges themselves or their microbial [[symbiosis|symbionts]] of chemicals that may be used to control [[virus]]es, [[bacteria]], [[tumor]]s and fungi.<ref>{{cite book |last1=Imhoff |first1=J.F. |last2=Stöhr |first2=R. |chapter=Sponge-Associated Bacteria |pages=43–44 |editor= Müller, W.E. |title=Sponges (Porifera): Porifera |publisher=[[Springer Science+Business Media|Springer]] |year=2003 |isbn=978-3-540-00968-9 }}</ref><ref name="pmid8297426">{{cite journal |last1=Teeyapant |first1=R. |last2=Woerdenbag |first2=H. J. |last3=Kreis |first3=P. |last4=Hacker |first4=J. |last5=Wray |first5=V. |last6=Witte |first6=L. |last7=Proksch |first7=P. |title=Antibiotic and cytotoxic activity of brominated compounds from the marine sponge Verongia aerophoba |journal=Zeitschrift für Naturforschung C |volume=48 |issue=11–12 |pages=939–45 |date=1993 |pmid=8297426 |doi=10.1515/znc-1993-11-1218 |s2cid=1593418 |doi-access=free }}</ref>

Lacking any protective shell or means of escape, sponges have evolved to synthesize a variety of unusual compounds. One such class is the oxidized fatty acid derivatives called [[oxylipin]]s. Members of this family have been found to have anti-cancer, anti-bacterial and anti-fungal properties. One example isolated from the Okinawan ''Plakortis'' sponges, [[plakoridine A]], has shown potential as a cytotoxin to murine lymphoma cells.<ref>{{cite journal |last1=Takeuchi |first1=Shinji |last2=Ishibashi |first2=Masami |last3=Kobayashi |first3=Junichi |title=Plakoridine A, a new tyramine-containing pyrrolidine alkaloid from the ''Okinawan marine'' sponge Plakortis sp |journal=Journal of Organic Chemistry |year=1994 |volume=59 |issue=13 |pages=3712–3713 |doi=10.1021/jo00092a039 }}</ref><ref>{{cite journal |last1=Etchells |first1=Laura L. |last2=Sardarian |first2=Ali |last3=Whitehead |first3=Roger C. |title=A synthetic approach to the plakoridines modeled on a biogenetic theory |journal=[[Tetrahedron Letters]] |date=18 April 2005 |volume=46 |issue=16 |pages=2803–2807 |doi=10.1016/j.tetlet.2005.02.124 }}</ref>

== See also ==
* [[Lists of sponges]]
* [[Sponge Reef Project]]
* [[3-alkylpyridinium]], compounds found in marine [[Haplosclerida]] sponges
*[[SpongeBob SquarePants]]

== References ==

{{Reflist}}

== Further reading ==

{{refbegin|30em}}
* {{cite book |author1=Hickman, C. |author2=Roberts, L. |author3=Larson, A. |year=2003 |title=Animal Diversity |edition=3rd |publisher=McGraw-Hill |location=New York |isbn=978-0-07-234903-0 |url-access=registration |url=https://archive.org/details/animaldiversity0003hick }}
* {{cite book |author=Ereskovsky, A.V. |title=The Comparative Embryology of Sponges|year=2010|location=Russia|publisher=Springer Science+Business Media|isbn=978-90-481-8575-7}}
* {{cite journal |author=Wörheide, G. |title=A hypercalcified sponge with soft relatives: Vaceletia is a keratose demosponge |journal=Molecular Phylogenetics and Evolution |volume=47 |issue=1 |pages=433–8 |date=April 2008 |pmid=18321733 |doi=10.1016/j.ympev.2008.01.021 |bibcode=2008MolPE..47..433W }}
{{refend}}

== External links ==

{{Commons category|Porifera}}

{{Wikispecies|Porifera}}
{{Wikibooks|Dichotomous Key|Porifera}}
* [http://www.biology.ualberta.ca/courses.hp/zool250/animations/Porifera.swf Water flow and feeding in the phylum Porifera (sponges)] – [[Adobe Flash|Flash]] animations of sponge body structures, water flow and feeding
* [http://www.spongepage.info/ Carsten's Spongepage], Information on the ecology and the biotechnological potential of sponges and their associated bacteria.
* [http://fcit.usf.edu/FLORIDA/lessons/tarpon/tarpon.htm History of Tarpon Springs sponge industry], [[Tarpon Springs, Florida]]
* [http://news.bbc.co.uk/2/hi/science/nature/7720836.stm Nature's 'fibre optics' experts]
* [https://web.archive.org/web/20010809125142/http://www.porifera.org/a/cif1.htm The Sponge Reef Project]
* [https://web.archive.org/web/20140724093014/http://www.qm.qld.gov.au/Find+out+about/Animals+of+Queensland/Sea+Life/Sponges Queensland Museum information about sponges]
* [https://web.archive.org/web/20121001131301/http://www.qm.qld.gov.au/Collections/Biodiversity+and+Geosciences/Biodiversity+Collections/Sessile+marine+invertebrates Queensland Museum Sessile marine invertebrates collections]
* [https://web.archive.org/web/20121001131444/http://www.qm.qld.gov.au/Research/Biodiversity/Areas+of+research/Sessile+marine+invertebrates Queensland Museum Sessile marine invertebrates research]
* [http://www.habitas.org.uk/marinelife/sponge_guide/ Sponge Guide for Britain and Ireland] {{Webarchive|url=https://web.archive.org/web/20081208120849/http://www.habitas.org.uk/marinelife/sponge_guide/ |date=2008-12-08 }}, Bernard Picton, Christine Morrow & Rob van Soest
* [http://www.marinespecies.org/porifera/ World Porifera database], the world list of extant sponges, includes a searchable database.
* [http://www.fao.org/3/AC286E/AC286E00.htm#TOC Sponges: World production and markets] // Food and Agriculture Organisation

{{Porifera}}
{{Animalia}}
{{Life on Earth}}
{{Portal bar|Marine Life|Animals|Earth sciences}}
{{Taxonbar|from=Q18960}}
{{Authority control}}

[[Category:Sponges|Sponges]]
[[Category:Aquatic animals]]
<!-- [[Category:Animal phyla]]

moved to "Porifera" redirect -->
[[Category:Ediacaran first appearances]]
[[Category:Parazoa]]