Systematics of Euplotes (Ciliophora, Hypotrichida); Toward Union of the Old and the New

SYNOPSIS. Prior to the general use of methods revealing the silverline system, members of the genus Euplotes were separated on the basis of body shape, sculpturing and arrangement of cirri. Since 1954, species have been separated on the basis of number of dorsolateral cilium rows, dorsal silverline system, number of fronto-ventral cirri, and form of the macronucleus. This paper describes E. charon Müller, 1773, E. quinquecarinatus Gelei, 1950, E. alatus Kahl, 1932, and E. bisulcatus Kahl, 1932, 4 species that are difficult to separate solely on the basis of the latter set of characters. By discussion of characters elucidated by a nigrosin-HgCl₂-formalin method, it is suggested that the following can form a basis for identification of members of this genus: 1) cortical sculpturing, 2) arrangement of all ciliary organelles, including dorsal and endoral cilia, and 3) details of the silverline system. Existing methods are indicated, some far more simple than silver methods, with which these characters can be elucidated.