Eurystomus

Abstract: This paper investigates the morphology and morphogenesis during binary fission of a Chinese population of Euplotes amieti Dragesco, 1970, a fresh water form which has previously not been well defined. This organism is morphologically very similar to the well-known Euplotes eurystomus but differs from the latter both in the number of dorsal kineties and the molecular data. According to the information obtained, it is characterized by a combination of features including nine frontoventral cirri, ca. 60 membranelles, 12–15 dorsal kineties, a macronucleus in the shape of the number 3, and a ‘double- eurystomus ’ type of silverline system. Its morphogenesis proceeds broadly in the same pattern as in its congeners. In this study, the SSU rRNA gene was sequenced for the first time, and phylogenetic analyses indicated that it is closely related to the eurystomus-aediculatus-woodruffi- complex. Considering the extreme similarities in morphology between E. amieti and E. eurystomus , we believe that the four sequences (four isolates) under the name of Euplotes eurystomus (No. FR873716; FR873717; EF193250; AJ310491 deposited in GenBank) are very likely from misidentified material; that is, they represent different populations of Euplotes amieti .