''Holothuria hilla'' 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 subgenus ''Mertensiothuria'' of the genus '' Holothuria''. Some common names include the contractile sea cucumber, the sand sifting sea cucumber and the tigertail sea cucumber, and in Hawaii it is known as the light spotted sea cucumber. It is found in the Indo-Pacific region and the

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 ...

Description

''Holothuria hilla'' is a cylindrical sea cucumber, tapering slightly at the posterior end. It can grow to a length of about and a diameter of . The integument is thin, soft and wrinkled. The dorsal surface is covered with 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 ...

modified into thorn-like conical papillae with broad bases, sometimes joined in pairs. These are creamy-white, in contrast to the pinkish, golden or brown background colour of the skin. The ventral surface is similar in colour but the papillae are ranged in four or five rows and are longer and yellowish. The mouth is on the underside and is surrounded by a ring of twenty, yellowish peltate

tentacle In zoology, a tentacle is a flexible, mobile, and elongated organ present in some species of animals, most of them invertebrates. In animal anatomy, tentacles usually occur in one or more pairs. Anatomically, the tentacles of animals work main ...

s. This species has

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 ...

but does not expel them defensively as do some other species.

Distribution and habitat

This species is found in the

Persian Gulf The Persian Gulf ( fa, خلیج فارس, translit=xalij-e fârs, lit=Gulf of Persis, Fars, ), sometimes called the ( ar, اَلْخَلِيْجُ ٱلْعَرَبِيُّ, Al-Khalīj al-ˁArabī), is a Mediterranean sea (oceanography), me ...

and the tropical west and central Indo-Pacific oceans, as far east as Hawaii, and even Panama. It is mainly found at less than , but occasionally as deep as , on sandy, rocky and coral substrates, in lagoons,

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 flat areas.

Ecology

''Holothuria hilla'' is a

detritivore Detritivores (also known as detrivores, detritophages, detritus feeders, or detritus eaters) are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). There are many kinds of invertebrates, ...

, raking sand into its mouth with its oral tentacles, extracting and digesting the bacteria, animal and vegetal particles, and voiding the sand through its

anus The anus (Latin, 'ring' or 'circle') is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, the residual semi-solid waste that remains after food digestion, which, d ...

. In this way it churns up significant areas of the seabed. Reproduction is either sexual, when the male and female liberate their

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 ...

, or asexual, by

fission Fission, a splitting of something into two or more parts, may refer to: * Fission (biology), the division of a single entity into two or more parts and the regeneration of those parts into separate entities resembling the original * Nuclear fissio ...

. Sexual reproduction mostly occurs at hotter times of year and asexual reproduction when it is cooler. In

Réunion Réunion (; french: La Réunion, ; previously ''Île Bourbon''; rcf, label= Reunionese Creole, La Rényon) is an island in the Indian Ocean that is an overseas department and region of France. It is located approximately east of the island ...

, where the species is rare, fission is the only breeding method that has been observed. The animal stops feeding and conceals itself while splitting; the missing parts regenerate and are often paler in colour than the original parts.

References

{{Taxonbar, from=Q2784929 Holothuriidae Fauna of the Indian Ocean Fauna of the Pacific Ocean Animals described in 1830 Taxa named by René Lesson