A further contribution to the taxonomy of the Trichodinidae (Ciliophora: Peritrichia) and a review of the taxonomic status of some fish ectoparasitic trichodinids

Abstract

The family Trichodinidae (Ciliophora: Peritrichia) includes nine genera of which the largest genus,Trichodina Ehrenberg, 1830, comprises more than 150 species. In order to provide uniform specific characteristics for taxonomic descriptions of trichodinids, Lom (1958) proposed the use of a set of standard taxonomic characteristics based on silver-impregnated specimens. Although widely in use, this method doesn't provide sufficient guidelines for describing the shape of the denticles, which forms the most important basis for species diagnosis. In this paper we propose a method to describe the shape of the denticles by constructing lines extending from the centre of the adhesive disc to the tip of the denticles, which provide fixed points of reference that can aid in an accurate description of the denticle elements. This method requires an enlargement of the denticles by means of a microscope drawing attachment or photomicrography. Since it employs existing characteristics, it can also be applied to previously published works. This method was used to re-evaluate our previously published data on trichodinid parasites of freshwater fish in order to elucidate the taxonomy of specimens collected in southern Africa and Israel. This applies mainly to a paper published in this journal by Basson, Van As & Paperna (1983). This taxonomic evaluation was also applied to additional data collected from various localities in southern Africa, Israel, Taiwan and Venezuela.