Pearsonothuria

{{Short description|Genus of sea cucumbers}} {{Speciesbox | name = ''Pearsonothuria graeffei'' | image = Pepino de mar (Pearsonothuria graeffei), Anilao, Filipinas, 2023-08-22, DD 33.jpg | image_caption = ''Pearsonothuria graeffei'' in the Philippines | status = LC | status_system = IUCN3.1 | status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Conand, C. |author2=Gamboa, R. |author3=Purcell, S. |date=2013 |title=''Pearsonothuria graeffei'' |volume=2013 |article-number=e.T180248A1605468 |doi=10.2305/IUCN.UK.2013-1.RLTS.T180248A1605468.en |access-date=19 November 2021}}</ref> | genus = Pearsonothuria | parent_authority = Levin, 1984<ref name=worms>{{cite WoRMS |author=Martinez, Olga |year=2006|title=''Pearsonothuria'' Levin in Levin, Kalinin & Stonik, 1984 |id=204297 |access-date=2012-02-16}}</ref> | species = graeffei | authority = Semper, 1868 <ref name=WoRMS>{{cite WoRMS |author=Paulay, Gustav |year=2010|title=''Pearsonothuria graeffei'' (Semper, 1868) |id=210772 |access-date=2012-02-16}}</ref> | synonyms = * ''Bohadschia drachi'' Cherbonnier, 1954 * ''Bohadschia graeffei'' (Semper, 1868) * ''Holothuria graffei'' Semper, 1868 * ''Stichopus troschelii'' Müller, 1854 | synonyms_ref = <ref name=WoRMS/> }}

'''''Pearsonothuria''''' is a genus of sea cucumbers in the family Holothuriidae. '''''Pearsonothuria graeffei''''' is the only species in the genus.<ref name=worms/> '''Graeffe's sea cucumber''' is found in the tropical Indo-Pacific Ocean and the type locality is Viti Island, Fiji.<ref name=WoRMS/> It is named after Eduard Heinrich Graeffe, Semper's coworker at the Museum Godeffroy.

==Description== ''Pearsonothuria graeffei'' is a roughly cylindrical, thin-walled sea cucumber that grows to about {{convert|30|cm}} in length.<ref name=Tropical>{{cite web |url=http://reefguide.org/pearsonothuriagraeffei.html |title=Graeffe's sea cucumber] |work=Tropical Reefs |access-date=2012-02-16 }}</ref> Its mouth, at one end, is surrounded by a ring of up to 24 leaf-like, paddle-shaped tentacles with black stalks which are black on the upper side and white beneath. The anus is at the other end of the body and there are several rows of tube feet along the underside. The colour of the adults is pale brown and white, with black speckles and small thornlike protuberances.

By contrast, the juveniles are brightly coloured, being white and blue or black, with a few large, yellow, thornlike projections. This colouration makes them closely resemble the sea slug, ''Phyllidia varicosa'', the bright colours of which warn predators of its toxicity. The appearance of the juvenile sea cucumbers begins to change when they grow larger than the slug and the mimicry is no longer effective.<ref name=InvertebrateZoology>{{cite web |url=http://www.flmnh.ufl.edu/malacology/pgraeffei.htm |title=Invertebrate of the month: ''Pearsonothuria graeffei'' |publisher=Florida Museum of Natural History |access-date=2012-02-16 }}</ref>

<gallery style="text-align:center;" mode="packed"> File:Holothuriidae - Bohadschia graeffei.jpg|A live juvenile individual of '' Pearsonothuria graeffei'', in situ off Madagascar File:Bohadschia graeffei.jpg|Adult specimen in the Maldives File:Pearsonothuria graeffei.jpg|Close-up on the tentacles File:Pearsonothuria graeffei bassin.JPG File:Pearsonothuria graeffei spawning.jpg|Sperm release during a mass spawning event on the island of Koh Tao, Thailand </gallery>

==Distribution== thumb|upright=1.1 ''Pearsonothuria graeffei'' is found in tropical parts of the Indo-Pacific Ocean. The range extends from the east coast of Africa to the Philippines, Indonesia and the South Pacific. It is found on the seabed and on coral reefs at depths down to about {{convert|25|m}}.<ref name=WoRMS/><ref name=Tropical/>

==Biology== ''Pearsonothuria graeffei'' is a scavenger and roams around on the seabed sifting through the sediment with its feeding tentacles. Any organic matter it finds is passed to its mouth by the tentacles.<ref>{{cite web |url=http://www.wildwatch.com/sightings/pearsonothuria-graeffei-leopard-sea-cucumber |title=''Pearsonothuria graeffei'' |work=Wildwatch.com |access-date=2012-02-16 }}</ref> Its daily activities start within a few minutes of dawn and continue until half an hour after sunset after which time it adopts an inactive stance with its rear end raised and its tentacles retracted into its mouth. It then remains immobile during the night.<ref>[http://www.sicb.org/meetings/2008/schedule/abstractdetails.php3?id=307 Behavioral Effects of Light on the Tropical Holothurian ''Pearsonothuria graeffei''] Society for Integrative and Behavioral Biology. Retrieved 2012-02-16.</ref> They are known to spawn simultaneously with other Echinoderms, including the crown-of-thorns starfish and the sea urchin ''Diadema setosum.''<ref>{{Cite journal|last=Scott|first=C. M.|last2=Mehrotra|first2=R.|last3=Urgell|first3=P.|date=2014-08-23|title=Spawning observation of ''Acanthaster planci'' in the Gulf of Thailand|url=https://www.researchgate.net/publication/281133738|journal=Marine Biodiversity|volume=45|issue=4|pages=621–622|doi=10.1007/s12526-014-0300-x }}</ref>

When threatened or disturbed, many sea cucumbers eject cuvierian tubules, thin white sticky strands of viscera, from their cloacas. ''Pearsonothuria graeffei'' seems reluctant to do this except under conditions of extreme stress. The threads of this species contain glycosides that are toxic to the aggressor. The effect of these neuro-toxins is to prevent nerve impulses being transmitted, an effect similar to that produced by cocaine. The chemicals, ''echinoside A'' and ''ds-echinoside A'', are being investigated for their possible use by humans as painkillers or anti-tumour drugs.<ref name=InvertebrateZoology/> Experiments in vitro show that they have marked anti-cancer activity in Hep G2 cells and that, when given to mice with H22 hepatocellular carcinoma tumours (liver cancer), the weight of the tumours was reduced by about 50%.<ref>{{cite journal |first1=Qin |last1=Zhao |year=2011 |title=''In vitro'' and ''in vivo'' anti-tumour activities of echinoside A and ''ds''-echinoside A from ''Pearsonothuria graeffei'' |journal=Journal of the Science of Food and Agriculture |volume=92 |issue=4 |pages=965–974 |doi=10.1002/jsfa.4678 |pmid=22012678 |display-authors=etal}}</ref>

==References== {{Reflist|colwidth=33em}}

==External links== * {{SealifePhotos|210772}}

Category:Sea cucumber genera Category:Monotypic echinoderm genera Category:Dendrochirotida Category:Echinoderms of the Indian Ocean Category:Echinoderms of the Pacific Ocean Category:Taxa named by Carl Semper Category:Taxa described in 1868