''Elpidia minutissima'' 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 ...

of deep-sea swimming

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 Family (from la, familia) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its ...

Elpidiidae Elpidiidae is a family of deep-sea sea cucumbers. They have a translucent body with long and stout podia acting like legs. The mouth is surrounded by thick and short oral tentacles, and the dorsal part often shows pairs of elongated podia as wel ...

. It 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, ...

and is found in the northern Pacific Ocean.

Description

Specimens collected from the Aleutian Trench averaged in length and had three pairs of dorsal podia whereas specimens collected from Station M in the northeastern Pacific Ocean at a depth of about had four pairs, two pairs on the dorsal surface and two pairs on the ventral surface, the hindermost of the ventral podia being shorter than the others. At times of low abundance, the average length of these sea cucumbers was similar to the specimens from the Aleutian Trench but at times of high abundance it increased to . It is possible that these two populations are not in fact the same species.

Ecology

''Elpidia minutissima'' feeds on

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 ...

on the

seabed The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as 'seabeds'. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

, the result of " marine snow" consisting of mucus, faeces and organic debris, that sink into the depths from surface waters. It plays an important part in the processing, utilization and redistribution of particles of organic material that has fallen to the sea bed. ''Elpidia minutissima'' is one of a number of echinoderm species that show great variations in population density. Researchers in one study found that, over a sixteen-year period, two deep sea holothurians, ''E. minutissima'' and '' Peniagone vitrea'', underwent a decline in density of the order of one to two magnitudes. It has been hypothesized that two factors that increase the likelihood of large swings in population are broadcast spawning and the possession of

planktotrophic Marine larval ecology is the study of the factors influencing dispersing larvae, which many marine invertebrates and fishes have. Marine animals with a larva typically release many larvae into the water column, where the larvae develop before met ...

larvae. These factors provide a positive feedback loop so that once populations decline, recovery is very slow. When individual organisms are further apart, broadcast spawning is less likely to result in fertilisation and this means fewer larvae available for recruitment.

References

Elpidiidae Animals described in 1971 {{Holothuroidea-stub