Morphology and phylogenetic analysis of two oxytrichid soil ciliates from China, Oxytricha paragranulifera n. sp. and Oxytricha granulifera Foissner and Adam, 1983 (Protista, Ciliophora, Hypotrichia).

Abstract

The morphology and infraciliature of two hypotrichous ciliates, Oxytricha paragranulifera n. sp. and Oxytricha granulifera Foissner and Adam, 1983, collected respectively from the surface of a sandy soil in the Huguang mangrove forest, Zhanjiang, China, and the surface of soil in a forest beside Ziwu Road, Xian, north-west China, were examined. O. paragranulifera n. sp. is characterized by an elongate body with slightly tapered anterior end, two macronuclear nodules and two micronuclei, paroral and endoral in Stylonychia-pattern, colourless cortical granules distributed in clusters or irregular short rows, adoral zone occupying 37 % of the body length, marginal rows almost confluent posteriorly, six dorsal kineties and three caudal cirri, caudal cirri and dorsal bristles almost indistinguishable when viewed in vivo. The well-known O. granulifera Foissner and Adam, 1983 was also redescribed and can be separated from the novel species by having cortical granules arranged along dorsal kineties and marginal rows on both sides (vs grouped in clusters as well as in short irregular rows), paroral and endoral in Oxytricha-pattern (vs in Stylonychia-pattern), macronuclear nodules obviously detached (vs adjacent) and a non-saline terrestrial habitat (vs saline terrestrial). The separation of these two taxa is also firmly supported by the molecular data, which show a significant difference between the two in their SSU rRNA gene sequences (similarity 97.1 %). Phylogenetic analyses based on SSU rRNA gene sequence data suggest a close relationship within the Oxytrichidae assemblage between O. paragranulifera n. sp. and O. granulifera.