Ceratothoa steindachneri Koelbel, 1878


C. steindachneri is an ectoparasite of the Lesser Weaver Fish (Echiichthys vipera (Cuvier)), inhabiting the buccal cavity of its host. It is between 15 and 23 mm in length with an oval body shape and recurved sharp dactyls. The head is immersed in the first pereonite and the basal articles of the antennae are expanded so that they touch each other. The coxae are rounded and are not extended.

Distribution and Habitat

C. steindachneri has been found in the buccal cavity of the Lesser Weaver Fish (Echiichthys vipera (Cuvier)) in four sites in Cornwall, at Isle of Grain in Kent, and at Les Minquiers in the Channel Islands, and appears to be spreading, having first become established in Cornwall (Horton & Okamura 2002).


Horton, T. 2000. Ceratothoa steindachneri (Isopoda: Cymothoidae) new to British waters with a key to north-east Atlantic and Mediterranean CeratothoaJournal of the Marine Biological Association of the UK 80, 1041-1052.

Horton, T. & Baillie, C. 2019. Cymothoid isopods in UK Waters. PMNHS Bulletin 11, 44-50.

Horton, T. & Okamura, B. 2002. The distribution of Ceratothoa steindachneri (Crustacea: Isopoda: Cymothoidae) parasitic in Echiichthys vipera in the north-east Atlantic. Journal of the Marine Biological Association of the UK 82, 415-7.

Naylor, E. & A. Brandt. 2015. Intertidal Marine Isopods. Synopses of the British Fauna (New Series), No. 3. Field Studies Council, for The Linnean Society of London.