''Thyonicola dogieli'' is a

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

species of

gastropod The gastropods (), commonly known as snails and slugs, belong to a large taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, from freshwater, and from land. T ...

mollusc Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

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 ...

Eulimidae Eulimidae is a family of very small parasitic sea snails, marine gastropod mollusks in the superfamily Vanikoroidea. Description These small parasitic snails live on (or in some cases in) the bodies of echinoderms such as sea cucumbers, sea ...

. It parasitises

sea cucumbers 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 northeastern Pacific Ocean.

Description

This slender elongated mollusc does not have a shell and takes the form of a long tube, coiled like a spring, or tied in knots, and filled with eggs. It holds the record as the longest gastropod mollusc in the world, one individual having been found to be long when uncoiled.

Ecology

''Thyonicola dogieli'' is a parasite of sea cucumbers such as ''

Cucumaria miniata ''Cucumaria miniata'' is a species of sea cucumber. It is commonly known as the orange sea cucumber or red sea cucumber due to its striking color. This northeast Pacific species is often found wedged in between rocks or crevices at the coast or ...

''. It inhabits the gut of the sea cucumber, being attached at the anterior end. It has no digestive tract and absorbs nutrients through its

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

. It is a

hermaphrodite In reproductive biology, a hermaphrodite () is an organism that has both kinds of reproductive organs and can produce both gametes associated with male and female sexes. Many Taxonomy (biology), taxonomic groups of animals (mostly invertebrate ...

; the

testis A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testostero ...

is located near the anterior end and the ovary near the posterior end (this enables the sperm to be carried to the eggs amid the flow of the contents of the host's gut). The body is filled with maturing eggs enclosed in cocoons. When the

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod ...

larvae, which have miniature coiled shells and operculums, are sufficiently developed, the cocoons are released into the sea cucumber's gut and pass out into the sea with its faeces. On encountering sea water the cocoons burst open and the free-living larvae are liberated. They are about long, and unless swallowed by a sea cucumber, they will soon die, However, any that are ingested undergo

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 ...

in the host's gut, lose their shell and mantle and burrow into the wall of the gut with the aid of a glandular secretion. As the juvenile mollusc grows, its posterior end pushes its way into the sea cucumber's body cavity, and the gonads develop, the interior of the mollusc becoming a brood pouch.

References

{{Taxonbar, from=Q14491853 Eulimidae Gastropods described in 1945