''Stichocotyle'' is a monospecific genus of

trematode Trematoda is a class of flatworms known as flukes. They are obligate internal parasites with a complex life cycle requiring at least two hosts. The intermediate host, in which asexual reproduction occurs, is usually a snail. The definitive host ...

s, in the monospecific family Stichocotylidae, which is itself in the monotypic order Stichocotylida. It comprises the single species ''Stichocotyle nephropis'', which is an internal

parasite 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 ...

of elasmobranch fishes. It was originally described from the Norway lobster, ''

Nephrops norvegicus ''Nephrops norvegicus'', known variously as the Norway lobster, Dublin Bay prawn, ' (compare langostino) or ''scampi'', is a slim, orange-pink lobster which grows up to long, and is "the most important commercial crustacean in Europe". It is n ...

'', by J. T. Cunningham in 1884. This flatworm is distinguished by a single ventral row of well separated suckers. ''Stichocotyle'' has not been seen since 1986, and it is possible that it is extinct. Like many parasites, it relied on multiple hosts, and its disappearance is hypothesized to be associated with declines in some of these hosts. The

thornback ray The thornback ray (''Raja clavata''), or thornback skate, is a species of ray fish in the family Rajidae. Distribution The Thornback ray is found in the Atlantic coastal waters of Europe and western Africa. It is also present from south Afri ...

''Raja clavata'' and the

barndoor skate The barndoor skate (''Dipturus laevis'') is a species of marine cartilaginous fish in the skate family Rajidae of the order Rajiformes. It is native to the northwestern Atlantic Ocean, and is found from the Grand Banks of Newfoundland and the ...

''Dipturus laevis'' were hosts for the adult form, and have declined because they are killed as

bycatch Bycatch (or by-catch), in the fishing industry, is a fish or other marine species that is caught unintentionally while fishing for specific species or sizes of wildlife. Bycatch is either the wrong species, the wrong sex, or is undersized or juve ...

in fisheries. The thornback ray is listed as "Near Threatened," and the barndoor skate is globally listed as "Endangered" on the IUCN Red List.

References

Parasites of crustaceans Trematode genera Monotypic protostome genera Aspidogastrea Taxobox binomials not recognized by IUCN {{trematoda-stub