''Eupentacta quinquesemita'' is a

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

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 ...

, a marine invertebrate with an elongated body, a leathery skin and tentacles surrounding the mouth. It is commonly known as the stiff-footed sea cucumber or white sea cucumber, and occurs on rocky coasts in the northeastern Pacific Ocean.

Description

''Eupentacta quinquesemita'' can grow to a length of up to . The tube feet are arranged in four longitudinal rows; they are non-retractable and give the animal a spiny appearance. The skin between the tube feet is smooth, but both body wall and tube feet contain calcareous ossicles that make them stiff. The mouth is surrounded by ten branched feeding

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, the two lowest ones being smaller than the rest. The general body colour is white, the tentacles (often the only parts of the animal that are visible) being creamy-white, often with yellowish or pinkish bases. Bits of shell or other fragments often adhere to the tube feet.

Distribution and habitat

''E. quinquesemita'' is found in the northeastern Pacific Ocean, its range extending from Alaska to California. It is found on rocky shores in low intertidal and shallow subtidal zones, where it tends to hide itself in crevices and under boulders. It is common among harbour installations, pilings and floats, especially where there is vigorous water movement. Larvae often settle in locations with strong currents among

hydroids Hydroids are a life stage for most animals of the class Hydrozoa, small predators related to jellyfish. Some hydroids such as the freshwater '' Hydra'' are solitary, with the polyp attached directly to the substrate. When these produce buds ...

and algae.

Ecology

A deposit and suspension feeder, ''E. quinquesemita'' uses its feeding tentacles to push material into its mouth, extracting the edible material and eliminating the unwanted debris. The larvae of a parasitic snail, ''

Thyonicola americana ''Thyonicola americana'' is a species of parasitic sea snail, a marine gastropod mollusc in the family Eulimidae. It infests the sea cucumbers '' Eupentacta quinquesemita'' and '' Eupentacta pseudoquinquesemita'' in Puget Sound and other par ...

'', enter in this way and develop into adults which invade the viscera while maintaining a connection to the gut lumen to release offspring. The sea cucumber is preyed on by several species of starfish, such as ''

Solaster stimpsoni ''Solaster stimpsoni'', common names Stimpson's sun star, sun star, orange sun star, striped sunstar, and sun sea star, is a species of starfish in the family Solasteridae. Description ''Solaster stimpsoni'' is a large species, growing up to 5 ...

'', ''

Pycnopodia helianthoides ''Pycnopodia helianthoides'', commonly known as the sunflower sea star, is a large sea star found in the northeast Pacific. The only species of its genus, it is among the largest sea stars in the world, with a maximum arm span of . Adult sunflow ...

'' and '' Leptasterias hexactis'', and fish such as the

kelp greenling The kelp greenling (''Hexagrammos decagrammus'') is a species of marine ray-finned fish belonging to the family Hexagrammidae, the greenlings. It occurs in the eastern Pacific Ocean Species description and etymology The kelp greenling was fir ...

(''Hexagrammos decagrammus''). This sea cucumber exhibits a seasonal pattern of evisceration, expelling its guts in the autumn and growing a new set in the spring, resulting in a high proportion of ''T. americana'' parasites not completing their life cycle, but not all individuals do this. Breeding takes place between March and May, females liberating large, yolky eggs into the sea where they are fertilised by sperm produced by the males. The larvae are well-ciliated but do not feed, developing their calcareous armour in about a fortnight before settling.

References

{{Taxonbar, from=Q2432938 Sclerodactylidae Animals described in 1867