Morphology and molecular phylogeny of a new freshwater ciliate Urosomoida sejongensis n. sp. (Ciliophora, Sporadotrichida, Oxytrichidae) from King George Island, Antarctica

Abstract

In this study, a new "non-oxytrichid Dorsomarginalia" ciliate, Urosomoida sejongensis n. sp. 18 discovered from freshwater of the King George Island, Antarctica, was investigated using 19 morphological, morphometrical, and molecular methods. Morphology of U. sejongensis is 20 characterized as follows: body shape slender to elongated;cortical granules spherical and colorless, 21 groups of granules formed patchy distribution;ring-shaped structures scattered in cytoplasm;27？30 22 adoral membranelles with undulating membranes in Oxytricha pattern;usually 17 frontal-ventral-23 transverse (FVT) cirri composed of 8 frontal, 3 postal ventral, 2 pretransverse ventral and 4 transverse 24 cirri;1 right and 1 left marginal rows;3 dorsal kineties with 1 dorsomarginal row, 3 caudal cirri;1 25 micronucleus between 2 macronuclear nodules. This new species mainly differs from other congeners 26 by the combination of following morphological features: a micronucleus, cortical granules, and 27 ciliatures (e.g., adoral membranelles, FVT cirri). Urosomoida sejongensis shows a nucleotide 28 similarity of 97.3% with U. agilis, type of this genus, using the SSU rDNA sequence. Molecular 29 phylogeny shows a non-monophyletic relationship among Urosomoida species and emphasizes the 30 need for further morphogenetic studies of this genus and other related species