Holothuria atra

{{Short description|Species of sea cucumber}} {{Speciesbox | image = Holothuria atra.jpg | image_caption = | status = LC | status_system = IUCN3.1 | status_ref = <ref name="iucn status 20 November 2021">{{cite iucn |author=Conand, C. |author2=Gamboa, R. |author3=Purcell, S. |date=2013 |title=''Holothuria atra'' |volume=2013 |article-number=e.T180421A1628832 |doi=10.2305/IUCN.UK.2013-1.RLTS.T180421A1628832.en |access-date=20 November 2021}}</ref> | genus = Holothuria | species = atra | authority = Jaeger, 1833 <ref name=WoRMS>{{cite WoRMS |author= Paulay, Gustav |year=2010 |title=''Holothuria (Halodeima) atra'' Jaeger, 1833 |id=148748 |accessdate=2012-01-20 |db=}}</ref> | synonyms = *''Halodeima atra'' Jaeger, 1833 *''Holothuria affinis'' Brandt, 1835 *''Holothuria amboinensis'' Semper, 1868 *''Holothuria radackensis'' Chamisso & Eysenhardt, 1821 *''Holothuria sanguinolenta'' Saville-Kent, 1893 | synonyms_ref = <ref name=WoRMS/> }}

'''''Holothuria atra''''', commonly known as the '''black sea cucumber''' or '''lollyfish''', is a species of marine invertebrate in the family Holothuriidae. It was placed in the subgenus ''Halodeima'' by Pearson in 1914, making its full scientific name ''Holothuria (Halodeima) atra''. It is the type species of the subgenus.<ref name=WoRMS/>

==Description== ''Holothuria atra'' is a sea cucumber that can grow to a length of {{convert|60|cm}} but {{convert|20|cm}} is a more common size. It has a smooth, pliable, entirely black skin which often has sand adhering to it, especially in smaller individuals. The mouth is on the underside at one end and is surrounded by a fringe of 20 black, branched tentacles. The anus is at the other end.<ref name=MSIP>[http://species-identification.org/species.php?species_group=nasc&id=55&menuentry=soorten ''Holothuria atra''] Marine Species Identification Portal. Retrieved 2012-01-20.</ref><ref name=SeaLifeBase>[http://www.sealifebase.org/summary/SpeciesSummary.php?id=50229 ''Holothuria atra'' Jaeger, 1833]. SeaLifeBase. Retrieved 2012-01-20.</ref>

<gallery style="text-align:center;" mode="packed"> Image:Holothuria atra in Pulau Perhentian, Malaysia.jpg|In Malaysia Image:Holothuria atra Thailand.jpg|In Thailand Image:Holothuria Maldives.JPG|In Maldives Image:Holothuria atra (3817431638).jpg|Drawing Image:HolothuriaAtra.jpg|Museum specimen </gallery>

==Distribution and habitat== ''Holothuria atra'' is found in the tropical Indo-Pacific region, its range extending from the Red Sea and East Africa to Australia. It is found on the seabed, in shallow waters on reefs and sand flats and in seagrass meadows at depths of up to {{convert|20|m}}.<ref name=WoRMS/><ref name=MSIP/> Its colouring makes it conspicuous but it is very often camouflaged by a coating of sand which may also serve to keep it cool by protecting it from the sun's rays. It favours reef flats where it is not fully exposed to the waves but the water is well aerated, and shallows beside slabs of rock from under which cool water wells out when the tide retreats. In such places it is often found in pools above the low tide mark which are warmed by the sun during the day. ''Holothuria atra'' seems to tolerate these high temperatures well and individuals appeared healthy and were feeding when the water temperature rose as high as 39 °C.<ref name=Ecological>[http://scholarspace.manoa.hawaii.edu/bitstream/handle/10125/7142/vol17n3-305-314.pdf?sequence=1 Ecological Observations on the Sea Cucumbers ''Holothuria atra'' and ''H. leucospilota'' at Rongelap Atoll, Marshall Islands] Retrieved 2012-01-20.</ref>

==Biology== ''Holothuria atra'' is an omnivore, sifting through the sediment with its tentacles and feeding on detritus and other organic matter. As a defence against predators, ''Holothuria atra'' emits a toxic red fluid when its skin is rubbed or damaged.<ref name=MSIP/> When attacked, it does not eject Cuvierian tubules in the way that some sea cucumbers do, but instead extrudes its internal organs through its anus.

It is not possible to distinguish between male and female ''Holothuria atra'' externally. Maturity is reached at a body length of about {{convert|16|cm}} and spawning mostly takes place during the summer and autumn although in equatorial waters it may take place all year round.<ref>{{cite journal |author=Abdel-Razek, F.A.|year=2005 |title=Reproductive biology of the tropical sea cucumber ''Holothuria atra'' (Echinodermata: Holothuroidea) in the Red Sea coast of Egypt |journal=Egyptian Journal of Aquatic Research |volume=31 |issue=2 |pages=383–402 |url=http://www.nodc-egypt.org/contacts_files/vol-31-2/Volume%2031%20%282%29%202005.PDF/26/Text.pdf |display-authors=etal}}</ref> It takes a minimum of 18-25 days for ''Holothuria atra'' to reach natural competence.<ref>{{Cite web|title=Induced spawning and larval rearing of the sea cucumbers, Bohadschia marmorata and Holothuria atra in Mauritius {{!}} Request PDF|url=https://www.researchgate.net/publication/242485393|access-date=2021-08-26|website=ResearchGate|language=en}}</ref> ''Holothuria atra'' is also fissiparous, meaning that it can reproduce by transverse fission.<ref name=SeaLifeBase/><ref>C. Conand, ''Asexual reproduction by fission in Holothuria atra: variability of some parameters in populations from the tropical Indo-Pacific'', Oceanologica acta, 1996, vol. 19, no 3-4, pp. 189-475 (29 ref.), pp. 209-216.</ref> It is mostly smaller individuals which divide in this way. A constriction appears, becomes deeper and deeper, and after some time the integument separates leaving two relatively wide but short individuals.<ref name=Ecological/> No sand adheres to the newly separated surfaces as there are no tube feet present to retain the grains.<ref name=Ecological/>

==Ecology== ''Holothuria atra'', like many echinoderms, engage in sediment bioturbation—a process which plays an important role in the health of coral reefs.<ref>{{Cite web|title=Sediment bioturbation and impact of feeding activity of Holothuria (Halodeima) Atra and Stichopus Chloronotus, two sediment feeding Holothurians, at Lizard Island, Great Barrier Reef|url=https://www.researchgate.net/publication/233686808|access-date=2021-08-25|website=ResearchGate|language=en}}</ref> ''Holothuria atra'' is often found associated with the polychaete worm ''Gastrolepidia clavigera'', a black worm which crawls about over the sea cucumber's skin.<ref name=WoRMS/> ''Holothuria atra'' seems to have few natural predators.<ref name=Ecological/>

''Lissocarcinus orbicularis'', a small crab, is known to live on this species in a commensal relationship.<ref>[http://scholarspace.manoa.hawaii.edu/bitstream/handle/10125/21792/Ayotte1.pdf?sequence=1 The relationship between holothurians and the portulid crab ''Lissocarcinus orbicularis'']</ref>

==Uses== In the Pacific Islands, ''Holothuria atra'' is collected by diving or by wading at low tide, and used for human consumption; its commercial value, however, is low.<ref name=SeaLifeBase/> On Guam, the toxic red fluid that ''Holothuria atra'' releases is utilized to drive octopuses out of hiding holes.<ref>{{Cite web|title=» Sea Stars, Sea Urchins and Other Echinoderms Of Guam|url=https://www.guampedia.com/sea-stars-sea-urchins-and-other-echinoderms-of-guam/|access-date=2021-08-25|website=www.guampedia.com|date=11 December 2011 }}</ref>

Compounds of potential biomedical importance are present in ''Holothuria atra'', including lectin, steroidal sapogenins and triterpene glycoside.<ref>{{Cite journal|last1=Bordbar|first1=Sara|last2=Anwar|first2=Farooq|last3=Saari|first3=Nazamid|date=2011-10-10|title=High-Value Components and Bioactives from Sea Cucumbers for Functional Foods—A Review|journal=Marine Drugs|volume=9|issue=10|pages=1761–1805|doi=10.3390/md9101761|issn=1660-3397|pmc=3210605|pmid=22072996|doi-access=free}}</ref> ----

==References== {{Reflist}}

Category:Holothuriidae Category:Echinoderms described in 1833 Category:Taxa named by Wilhelm Friedrich Jaeger