''Pearsonothuria'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

of sea cucumbers in the

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

Holothuriidae Holothuriidae is a Family (biology), family of sea cucumbers, a type of echinoderm. Description Members of the family Holothuriidae have thick fleshy bodies and several rows of tube feet which are used for moving around and for adhering to the s ...

. ''Pearsonothuria graeffei'' is the only

species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...

in the genus. Graeffe's sea cucumber is found in the tropical

Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...

Ocean and the type locality is Viti Island,

Fiji Fiji, officially the Republic of Fiji, is an island country in Melanesia, part of Oceania in the South Pacific Ocean. It lies about north-northeast of New Zealand. Fiji consists of an archipelago of more than 330 islands—of which about ...

. It is named after

Eduard Heinrich Graeffe Eduard Heinrich Graeffe or Gräffe (27 December 1833, Zurich – 23 April 1916 Ljubljana {{Infobox settlement , name = Ljubljana , official_name = , settlement_type = Capital city , image_skyline = {{multiple ...

, Semper's coworker at the

Museum Godeffroy The Museum Godeffroy was a museum in Hamburg, Germany, which existed from 1861 to 1885. The collection was founded by Johann Cesar VI. Godeffroy, who became a wealthy shipping magnate a few years after the expansion of the trade towards Australia ...

Description

''Pearsonothuria graeffei'' is a roughly cylindrical, thin-walled sea cucumber that grows to about in length. 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 Tube or tubes may refer to: * Tube (2003 film), ''Tube'' (2003 film), a 2003 Korean film * "Tubes" (Peter Dale), performer on the Soccer AM#Tubes, Soccer AM television show * Tube (band), a Japanese rock band * Tube & Berger, the alias of dance/e ...

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 Sea slug is a common name for some Marine biology, marine invertebrates with varying levels of resemblance to terrestrial Slug, slugs. Most creatures known as sea slugs are gastropods, i.e. they are Sea snail, sea snails (marine gastropod moll ...

, ''

Phyllidia varicosa ''Phyllidia varicosa'' is a species of sea slug, a dorid nudibranch, a shell-less marine (ocean), marine gastropod mollusc in the family Phyllidiidae.Bouchet, P. (2015)''Phyllidia varicosa'' Lamarck, 1801.In: MolluscaBase (2015). Accessed throu ...

'', the bright colours of which warn

predators Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill ...

of its

toxicity Toxicity is the degree to which a chemical substance or a particular mixture of substances can damage an organism. Toxicity can refer to the effect on a whole organism, such as an animal, bacteria, bacterium, or plant, as well as the effect o ...

. The appearance of the juvenile sea cucumbers begins to change when they grow larger than the slug and the

mimicry In evolutionary biology, mimicry is an evolved resemblance between an organism and another object, often an organism of another species. Mimicry may evolve between different species, or between individuals of the same species. In the simples ...

is no longer effective. File:Holothuriidae - Bohadschia graeffei.jpg, A live juvenile individual of '' Pearsonothuria graeffei'',

in situ is a Latin phrase meaning 'in place' or 'on site', derived from ' ('in') and ' ( ablative of ''situs'', ). The term typically refers to the examination or occurrence of a process within its original context, without relocation. The term is use ...

off

Madagascar Madagascar, officially the Republic of Madagascar, is an island country that includes the island of Madagascar and numerous smaller peripheral islands. Lying off the southeastern coast of Africa, it is the world's List of islands by area, f ...

File:Bohadschia graeffei.jpg, Adult specimen in the

Maldives The Maldives, officially the Republic of Maldives, and historically known as the Maldive Islands, is an Archipelagic state, archipelagic country in South Asia located in the Indian Ocean. The Maldives is southwest of Sri Lanka and India, abou ...

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

Distribution

''Pearsonothuria graeffei'' is found in tropical parts of the

Ocean. The range extends from the east coast of Africa to the

Philippines The Philippines, officially the Republic of the Philippines, is an Archipelagic state, archipelagic country in Southeast Asia. Located in the western Pacific Ocean, it consists of List of islands of the Philippines, 7,641 islands, with a tot ...

Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...

and the South Pacific. It is found on the seabed and on coral reefs at depths down to about .

Biology

''Pearsonothuria graeffei'' is a

scavenger Scavengers are animals that consume Corpse decomposition, dead organisms that have died from causes other than predation or have been killed by other predators. While scavenging generally refers to carnivores feeding on carrion, it is also a he ...

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. 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. They are known to spawn simultaneously with other Echinoderms, including the

crown-of-thorns starfish The crown-of-thorns starfish (frequently abbreviated to COTS), ''Acanthaster planci'', is a large starfish that preys upon hard, or stony, coral polyps (Scleractinia). The crown-of-thorns starfish receives its name from venomous thornlike spines ...

and the sea urchin '' Diadema setosum.'' When threatened or disturbed, many sea cucumbers eject

cuvierian tubules Cuvierian tubules are clusters of fine tubes located at the base of the respiratory tree in some sea cucumbers in the genera ''Bohadschia'', ''Holothuria'' and '' Pearsonothuria'', all of which are included in the family Holothuriidae. The tubule ...

, thin white sticky strands of viscera, from their

cloaca A cloaca ( ), : cloacae ( or ), or vent, is the rear orifice that serves as the only opening for the digestive (rectum), reproductive, and urinary tracts (if present) of many vertebrate animals. All amphibians, reptiles, birds, cartilagin ...

s. ''Pearsonothuria graeffei'' seems reluctant to do this except under conditions of extreme stress. The threads of this species contain

glycoside In chemistry, a glycoside is a molecule in which a sugar is bound to another functional group via a glycosidic bond. Glycosides play numerous important roles in living organisms. Many plants store chemicals in the form of inactive glycosides. ...

s 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 Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...

. The chemicals, ''echinoside A'' and ''ds-echinoside A'', are being investigated for their possible use by humans as

painkillers An analgesic drug, also called simply an analgesic, antalgic, pain reliever, or painkiller, is any member of the group of drugs used for pain management. Analgesics are conceptually distinct from anesthetics, which temporarily reduce, and in so ...

or anti-tumour drugs. Experiments

in vitro ''In vitro'' (meaning ''in glass'', or ''in the glass'') Research, studies are performed with Cell (biology), cells or biological molecules outside their normal biological context. Colloquially called "test-tube experiments", these studies in ...

show that they have marked anti-cancer activity in

Hep G2 Hep G2 (or HepG2) is a human liver cancer cell line. Hep G2 is an immortal cell line which was derived in 1975 from the liver tissue of a 15-year-old Caucasian male from Argentina with a well-differentiated hepatocellular carcinoma. ...

cells and that, when given to mice with H22

hepatocellular carcinoma Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer in adults and is currently the most common cause of death in people with cirrhosis. HCC is the third leading cause of cancer-related deaths worldwide. HCC most common ...

tumours (liver cancer), the weight of the tumours was reduced by about 50%.

References

External links

* {{Taxonbar, from=Q18585248, from2=Q910552 Holothuroidea genera Monotypic echinoderm genera Dendrochirotida Echinoderms of the Indian Ocean Echinoderms of the Pacific Ocean Taxa named by Carl Semper Taxa described in 1868