Clarification of the Taxonomic Identification of Euplotes eurystomus Kahl and E. aediculatus Pierson

Abstract

A careful morphological comparison was made between 2 similar, often confused species of the genus Euplotes eurystomus and aediculatus. The studies were made on specimens prepared by 2 different methods: stained with picro-indigo-carmine and impregnated with silver (Chatton-Lwoff, as modified by Corliss, 1953). Living animals were observed with a prototype Francon-Yamamoto differential polarizing interference microscope. The number of lateral dorsal kinetics was 8 in E. aediculatus and 10 in E. eurystomus. The per-sistomal cavity of E. eurystomus transected the anterior-posterior body axis while that of E. aediculatus nearly paralleled it. The anal cirri were V-shaped in both species, but the distance between the posterior edge of the buccal cavity and the median and cirrus was greater in E. eurystomus. The macronucleus from the ventral view was "3"-shaped in E. eurystomus, while in E. aediculatus it was a mirror image "C." E. aediculatus had a niche in the right border of the buccal cavity. The right edge of the median lip appeared in living animals of both species as a thin, waving, undulating structure.