Caulerpa taxifolia

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Caulerpa taxifolia is a species of green seaweed, an alga of the genus Caulerpa, native to tropical waters of the Pacific Ocean, Indian Ocean, and Caribbean Sea.[1] The species name taxifolia arises from the resemblance of its leaf-like fronds[2] to those of the yew (Taxus). Script error: No such module "Unsubst".

A strain of the species bred for use in aquariums has established non-native populations in waters of the Mediterranean Sea, the United States, and Australia.[3] It is one of two species of algae listed in 100 of the World's Worst Invasive Alien Species compiled by the IUCN Invasive Species Specialist Group.[4]

Description

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Two illustrations (Fig 1 . 4-5) of C. taxifolia displaying its "leaf" and rhizome structures (Fig 1 . 1-3 are illustrations of C. sertularioides)

C. taxifolia is light green[2] with stolons (stems) on the sea floor, from which sparsely-branched upright fronds of approximately 20–60 cm (8–24 in) in height arise.[5] Algae in the genus Caulerpa synthesize a mixture of toxins[6] termed caulerpicin, believed to impart a peppery taste to the plants.[7] The effects of the specific toxin synthesized by C. taxifolia, caulerpenyne, have been studied,[8][9] with extracts from C. taxifolia being found to negatively affect P-glycoprotein-ATPase in the sea sponge G. cydonium.[10]

Like all members of the genus Caulerpa, C. taxifolia consists of a single cell with many nuclei. The algae has been identified as the largest known single-celled organism.[11] Wild-type C. taxifolia is monoecious.[12]

Use in aquaria

Caulerpa species are commonly used in aquaria for their aesthetic qualities and ability to control the growth of undesired species.[13] C. taxifolia has been cultivated for use in aquaria in western Europe since the early 1970s.[14] A clone of the alga that was resistant to cold was observed in the tropical aquarium at the Wilhelma Zoo in Stuttgart[15] and further bred by exposure to chemicals and ultraviolet light.[16] The zoo distributed the strain to other aquaria, including the Oceanographic Museum of Monaco.[15]

The aquarium strain is morphologically identical to native populations of the species.[2] However, a 2008 study found that a population of the aquarium strain near Caloundra, Australia exhibited markedly reduced sexual reproduction, with only male plants present during some reproductive episodes.[12] The aquarium strain can survive out of water for up to 10 days in moist conditions, with 1 cm fragments capable of producing viable plants.[17]

Status as invasive species

Outside its native range, C. taxifolia is listed as an invasive species.[18][19] It is one of two algae on the list of the world's 100 worst invasive species compiled by the IUCN Invasive Species Specialist Group (alongside Wakame).[4] The species is able to thrive in heavily polluted waters,[20] possibly contributing to its spread in the Mediterranean.[21]

Presence in the Mediterranean Sea

The presence of C. taxifolia in the Mediterranean was first reported in 1984[22] in an area adjacent to the Oceanographic Museum of Monaco.[23] Alexandre Meinesz, a marine biologist, attempted to alert Moroccan and French authorities to the spread of the strain in 1989,[15] but the governments failed to respond to his concerns.[24] The occurrence of the strain is generally believed to be due to an accidental release by the museum,[2][25] but Monaco rejected the attribution and instead claimed that the observed algae was a mutant strain of C. mexicana.[24] By 1999, scientists agreed that it was no longer possible to eliminate the presence of C. taxifolia in the Mediterranean.[24]

A study published in 2002 found that beds of Posidonia oceanica in the Bay of Menton were not negatively affected eight years after colonization by C. taxifolia.[26] Other published studies have shown that fish diversity and biomass are equal or greater in Caulerpa meadows than in seagrass beds[27] and that Caulerpa had no effect on composition or richness of fish species.[28]

Studies in 1998[14] and 2001[22] found that the strain observed in the Mediterranean was genetically identical to aquarium strains, with similarities to an additional population in Australia.

Presence in Australia

A 2007 study found that a native bivalve mollusc species was negatively affected by the presence of C. taxifolia, but that the effect was not necessarily different from that of native seagrass species.[29] A 2010 study indicated that the effect of detritus from C. taxifolia negatively impacted abundance and species richness.[30]

Presence in California

C. taxifolia was found in waters near San Diego, California, in 2000,[31] where chlorine bleach was used in efforts to eradicate the strain.[32] The strain was declared eradicated from Agua Hedionda Lagoon in 2006.[33] California passed a law in 2001 forbidding the possession, sale, transport, or release of Caulerpa taxifolia within the state.[34] The Mediterranean clone of C. taxifolia was listed as a noxious weed in 1999[35] by the Animal and Plant Health Inspection Service, prohibiting interstate sale and transport of the strain without a permit under the Noxious Weed Act and Plant Protection Act.[23][36]

Other negative effects

C. taxifolia may become entangled in fishing gear and boat propellers.[3]

Control methods

C. taxifolia may be controlled via mechanical removal, poisoning with chlorine, or application of salt.[5] Researchers at the University of Nice investigated possible use of a species of sea slug, Elysia subornata, as a possible natural control method, but found that it was not suitable for use in the Mediterranean due to cold winter water temperatures and insufficient population density.[37]

Gallery

See also

References

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  5. ↑ a b Script error: No such module "citation/CS1".
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  8. ↑ Script error: No such module "Citation/CS1".
  9. ↑ Script error: No such module "Citation/CS1".
  10. ↑ Script error: No such module "citation/CS1".
  11. ↑ Script error: No such module "Citation/CS1".
  12. ↑ a b Script error: No such module "Citation/CS1".
  13. ↑ Script error: No such module "citation/CS1".
  14. ↑ a b Script error: No such module "Citation/CS1".
  15. ↑ a b c Script error: No such module "citation/CS1".
  16. ↑ Script error: No such module "Citation/CS1".
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  18. ↑ Script error: No such module "Citation/CS1".
  19. ↑ Script error: No such module "citation/CS1".
  20. ↑ Script error: No such module "citation/CS1".
  21. ↑ Script error: No such module "Citation/CS1".
  22. ↑ a b Script error: No such module "Citation/CS1".
  23. ↑ a b Script error: No such module "citation/CS1".
  24. ↑ a b c Script error: No such module "citation/CS1".
  25. ↑ Script error: No such module "Citation/CS1".
  26. ↑ Script error: No such module "Citation/CS1".
  27. ↑ Relini, G., M Relini, and G. Torchia. (1998) Fish biodiversity in a Caulerpa taxifolia meadow in the Ligurian Sea. Italian Journal of Zoology 65 Supplement:465-470.
  28. ↑ Script error: No such module "Citation/CS1".
  29. ↑ Script error: No such module "Citation/CS1".
  30. ↑ Script error: No such module "Citation/CS1".
  31. ↑ Script error: No such module "Citation/CS1".
  32. ↑ Script error: No such module "Citation/CS1".
  33. ↑ Script error: No such module "citation/CS1".
  34. ↑ Script error: No such module "citation/CS1".
  35. ↑ Script error: No such module "citation/CS1".
  36. ↑ Script error: No such module "citation/CS1".
  37. ↑ Script error: No such module "Citation/CS1".

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Further reading

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  • Theodoropoulos, David. 2003. Invasion Biology: Critique of a Pseudoscience. pages 42,159. Avvar Books, Blythe, CA. 237 p. Template:ISBN

External links

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