Redescription of two Euplotes species (Ciliophora, Euplotida) from Yangtze River Estuary, China, with a note on the distributions of this genus in China

Abstract

Ciliates are important unicellular organisms in the studies of biomolecules, genetics, and evolution. Euplotids are a highly diversified and widely distributed group. The morphology of two euplotids, Euplotes dominicanus and E. parkei, isolated from the Yangtze River Estuary, China, were investigated based on live observation, protargol-, and Chatton-Lwoff staining methods. The Chinese population of E. dominicanus resembles the original abyssal population except for having two caudal cirri and seven dorsolateral kineties. The Chinese population of E. parkei corresponds well with the original description in size, having eight frontoventral cirri, two marginal cirri, and a double-eurystomus dorsal silverline system. The diagnoses were improved by incorporating newly obtained data, detailed illustrations, and photomicrographs were supplemented. Euplotes parkei sensu needs to be reinvestigated. Phylogenetic analyses based on SSU rRNA gene sequence data confirmed the branching position of the two taxa within the genus Euplotes. The geographical distribution of the genus Euplotes in China was also briefly reviewed, and further exploration is needed in the brackish habitat, particularly focusing on the estuary zone.