View source for Apodida

{{Short description|Order of sea cucumbers}}
{{Automatic taxobox
| image = Euapta godeffroyi1.jpg
| image_caption = ''[[Euapta godeffroyi]]''
| taxon = Apodida
| subdivision = 
* [[Chiridotidae]]
* [[Myriotrochidae]]
* [[Synaptidae]]
| synonyms = 
* Apoda [Variant spelling]
* Synaptida
}}

'''Apodida''' is an [[order (biology)|order]] of littoral to deep-sea, largely [[Fauna#Infauna|infaunal]] [[Holothuroidea|holothurians]], sea cucumbers. This order comprises three families, 32 [[genus|genera]] and about 270 known [[species]], called '''apodids''', "without feet".

==Characteristics==
These sea cucumbers are vagile holothurians with an elongated shape (up to 3 meters for ''[[Synapta maculata]]''), worm or snake-like. 
Their shape is adapted for burrowing through the sediment, sometimes in a fashion similar to [[earthworm]]s. Their mouth is surrounded with 10-25 pinnate or peltate tentacles. The absence of tube feet gives the order its name, ''Apodida'' meaning ''without feet'' : they move by crawling on the sediment, hence they need flat bottoms with few current. Members of this order have a [[circum-oral ring]] and [[tentacle]]s, but do not have [[tube feet]] or [[radial canal]]s. They also lack the complex respiratory trees found in other sea cucumbers, and [[Aquatic respiration|respire]] and excrete nitrogenous waste through their skin.<ref>{{cite book |author= Barnes, Robert D. |year=1982 |title= Invertebrate Zoology |publisher= Holt-Saunders International |location= Philadelphia, PA|pages= 981–996|isbn= 0-03-056747-5}}</ref>

The ossicles, minute calcareous plates embedded in the skin and characteristic of each species, can include wheel and anchor shapes.<ref>[http://www.dnr.sc.gov/marine/sertc/Sea_Cucumber_key.pdf An illustrated key to the sea cucumbers of the South Atlantic Bight] Retrieved 2012-02-12.</ref>

== List of families ==
This order contains 3 families, consisting in 32 genera in total, for 270 known species. 
* family [[Chiridotidae]] <small>Östergren, 1898</small>
* family [[Myriotrochidae]] <small>Théel, 1877</small>
* family [[Synaptidae]] <small>Burmeister, 1837</small>
* genus ''[[Achistrum]]'' <small>Etheridge, 1881</small>

{{clr}}
<gallery style="text-align:center;" mode="packed">
File:Chiridota heheva.jpg|''[[Chiridota hydrothermica]]''
File:Polycheira rufescens.JPG|''[[Polycheira rufescens]]''
File:Euapta godeffroi.jpg|''[[Euapta godeffroyi]]''
File:Euapta lappa.jpg|''[[Euapta lappa]]''
File:Polyplectana kefersteinii.jpg|''[[Polyplectana kefersteinii]]''
File:Synapta maculata 2.jpg|''[[Synapta maculata]]''
File:Synaptula lamperti (Sea cucumber).jpg|''[[Synaptula lamperti]]''
</gallery>

==References==
{{Reflist}}

{{Taxonbar|from=Q618825}}

[[Category:Apodida| ]]
[[Category:Echinoderm orders]]


{{Holothuroidea-stub}}