Trichodinid ciliates (Peritrichia : Trichodinidae) from the Bay of Kiel, with description of Trichodina claviformis sp n.

Investigations on the epizoic fauna of Gadus morhua (L.), Platichthys flesu s (L.) and Oncorhynchus mykiss (Walbaum) from the Kiel Fjord and Kiel Eight were carried out from September 1996 to March 1997. Smears from 120 G. mor hua and 92 P. flesus caught using fish traps and trammel nets, and of 35 O. mykiss obtained from a local fish farm in the Kiel Fjord revealed the pres ence of three species of trichodinid ciliates, Trichodina claviformis sp. n ., Trichodina jadranica Haider, 1964 and Trichodona raabei Lom, 1962. The n ew species can be distinguished from other trichodinids by its large size i n combination with the characteristically shaped adhesive disc containing d enticles with club-like formed thorns. The thorns are directed anteriorly a nd not towards the centre of the adhesive disc. As the Kiel Eight and Kiel Fjord are new locality records for T. jadranica and T. raabei, morphologica l data are provided for both species. Trichodina claviformis is the first r ecord of a peritrichous mobiline ciliate from Atlantic cod of the Baltic Se a. An identification key for 16 Trichodina species occurring on Baltic Sea fishes is provided based on the morphology of the adhesive disc and other w ell-established features. The occurrence of trichodinid ciliates on G. morh ua and P. flesus in the Baltic Sea is discussed, especially considering the biology of the host and a possible host specificity of the species.