''Holothuria (Roweothuria) poli'', also known as the white spot cucumber, is a species of

sea cucumber Sea cucumbers are echinoderms from the class Holothuroidea (). They are marine animals with a leathery skin and an elongated body containing a single, branched gonad. Sea cucumbers are found on the sea floor worldwide. The number of holothuria ...

in the family Holothuridae and the subgenus ''Roweothuria.'' The species was first described by the Italian doctor and naturalist Stefano delle Chiaje in 1824. The species' range has been documented as being in the

Mediterranean Sea The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the ea ...

Red Sea The Red Sea ( ar, البحر الأحمر - بحر القلزم, translit=Modern: al-Baḥr al-ʾAḥmar, Medieval: Baḥr al-Qulzum; or ; Coptic: ⲫⲓⲟⲙ ⲛ̀ϩⲁϩ ''Phiom Enhah'' or ⲫⲓⲟⲙ ⲛ̀ϣⲁⲣⲓ ''Phiom ǹšari''; T ...

, and the

Bay of Biscay The Bay of Biscay (), known in Spain as the Gulf of Biscay ( es, Golfo de Vizcaya, eu, Bizkaiko Golkoa), and in France and some border regions as the Gulf of Gascony (french: Golfe de Gascogne, oc, Golf de Gasconha, br, Pleg-mor Gwaskogn), ...

Description

''Holothuria poli'' is cylindrical and grows to a length of about and a width of . At the anterior end is a crown of retractable tentacles surrounding the mouth; at the posterior end is the cloacal opening. The thick leathery skin contains embedded calcareous

sclerite A sclerite (Greek , ', meaning "hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...

s and has blackish spots on a mottled background of brown and grey. The ventral surface is somewhat paler than the dorsal surface, which has numerous low tubercles tipped with white. The longitudinal rows of

tube feet Tube feet (technically podia) are small active tubular projections on the oral face of an echinoderm, whether the arms of a starfish, or the undersides of sea urchins, sand dollars and sea cucumbers; they are more discreet though present on britt ...

exude mucus to which sand and detritus adhere, often concealing the animal's appearance. This species is often confused with '' Holothuria tubulosa'', which has a similar distribution.

Distribution and habitat

''Holothuria poli'' is found in the East Atlantic Ocean, between the

Canary Islands The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Morocc ...

and the

, in the

and in the

; its occurrence in the Red Sea is likely as a result of its larvae passing through the

Suez Canal The Suez Canal ( arz, قَنَاةُ ٱلسُّوَيْسِ, ') is an artificial sea-level waterway in Egypt, connecting the Mediterranean Sea to the Red Sea through the Isthmus of Suez and dividing Africa and Asia. The long canal is a popular ...

, a process known as anti-Lessepsian migration. It inhabits the seabed, usually at depths down to about , but has been observed on a muddy substrate off the coast of Tunisia at much greater depths (). It is found on sand or rock, and favours

seagrass meadow A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and ...

s and areas with green

seaweed Seaweed, or macroalgae, refers to thousands of species of macroscopic, multicellular, marine algae. The term includes some types of '' Rhodophyta'' (red), ''Phaeophyta'' (brown) and ''Chlorophyta'' (green) macroalgae. Seaweed species such as ...

such as ''

Caulerpa ''Caulerpa'' is a genus of seaweeds in the family Caulerpaceae (among the green algae). They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world. A species in the Mediterran ...

''.

Ecology

''Holothuria poli'' is a limnivore, using the tentacles round its mouth to gather up sediment and shovelling this

detritus In biology, detritus () is dead particulate organic material, as distinguished from dissolved organic material. Detritus typically includes the bodies or fragments of bodies of dead organisms, and fecal material. Detritus typically hosts commun ...

into its mouth. The material is sorted in the gut, with organic particles being digested while sand and other indigestible material is mixed with mucus and formed into balls which are voided in a string of balls through the anus. In this way, it has been calculated that the sea cucumbers in a square metre of sand can "process" nearly of sediment in a year. This sea cucumber is sometimes parasitised by the worm-like

sea snail Sea snail is a common name for slow-moving marine gastropod molluscs, usually with visible external shells, such as whelk or abalone. They share the taxonomic class Gastropoda with slugs, which are distinguished from snails primarily by the ...

Entoconcha mirabilis ''Entoconcha mirabilis'' is a species of very small parasitic sea snail, a marine gastropod mollusk in the family Eulimidae. This species is the only one known to exist within the genus, '' Entoconcha''.J. Müller, 1852. Gofas, S.; Le Renard, ...

''. It has few predators because of the thick leathery skin and the presence of the bony sclerites in the integument. The sexes are separate in this species and reproduction takes place between November and January. The animals rear up, adopting L-shaped postures, to release clouds of

gamete A gamete (; , ultimately ) is a haploid cell that fuses with another haploid cell during fertilization in organisms that reproduce sexually. Gametes are an organism's reproductive cells, also referred to as sex cells. In species that produce t ...

s into the

water column A water column is a conceptual column of water from the surface of a sea, river or lake to the bottom sediment.Munson, B.H., Axler, R., Hagley C., Host G., Merrick G., Richards C. (2004).Glossary. ''Water on the Web''. University of Minnesota-D ...

; there seems to be some sort of synchronisation mechanism for this release. The larvae are

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

ic and pass through several stages before settling on the seabed and undergoing

metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation. Some inse ...

into juveniles.

References

{{Taxonbar, from=Q2490776 Holothuriidae Fauna of the Atlantic Ocean Fauna of the Mediterranean Sea Fauna of the Red Sea Taxa named by Stefano delle Chiaje Animals described in 1824