Two new marine ciliates, Euplotes sinicus sp. nov. and Euplotes parabalteatus sp. nov., and a new small subunit rRNA gene sequence of Euplotes rariseta (Ciliophora, Spirotrichea, Euplotida).

The morphology, infraciliature and silverline system of two marine Euplotes, Euplotes sinicus sp. nov. and Euplotes parabalteatus sp. nov., isolated from seawater near Qingdao, China, were investigated. E. sinicus is characterized by having conspicuous dorsal ridges, a single marginal cirrus and a silverline system of the double-patella-I type. E. parabalteatus is an extremely small form (only about 35 mum long) with 6-7 dorsal kineties and a silverline system of the double-eurystomus type. Small subunit (SSU) rRNA-based phylogenetic trees were constructed with three different methods and these firmly demonstrated that the novel species represent two distinct phylogenetic lineages within the genus Euplotes, branching as a sister group to all other sequenced congeners. In addition, the SSU rRNA gene of another rare, morphologically similar form, Euplotes rariseta, was sequenced. This revealed the phylogenetic position of E. rariseta to be basal to one of the major groups of Euplotes rather than close to Euplotes nobilii.