Clypeoniscus cantacuzenei Bourdon, 1967

ID Difficulty



C. cantacuzenei is a parasite of the marine isopod Cleantis prismatica. Like other members of the Cabiropidae family, it is a protandrous hermaphrodite. The small male cryptoniscus stage (about 0.5 mm in length) infects the host, becoming female, developing internally and losing obvious isopod characteristics. This male cryptoniscus larva is the only form of this isopod that is easily visible or identifiable, appearing as a bright red speck on the host's body (though this colour is quickly lost in ethanol). It can be distinguished from the cryptoniscus larva of other species in the genus by its association with C. prismatica and by the presence of two (rather than three) teeth on its coxal plates. Note that this species is not included in Naylor & Brandt (2015).

Distribution and Habitat

The host species, Cleantis prismatica, is found around the coasts of Britain and Ireland, but the distribution of C. cantacuzenei is unknown given that it has so far only been recorded once in Britain, from Cresswell in Northumberland. It may be expected to occur elsewhere and should be looked out for on its host, though Jenkins & Griffin (2020) note that infestation levels are likely to be rather low where it does occur.


Jenkins, A. & R. Griffin. 2020. First record of the isopod parasite Clypeoniscus cantacuzenei (Crustacea: Isopoda) in the UK and the introduction of a key to the cryptoniscus stage of genus Clypeoniscus of UK Waters. Cahiers de Biologie Marine 61, 501-5.