Morphology, ontogeny and molecular phylogeny of a novel saline soil ciliate, Urosomoida paragiliformis n. sp. (Ciliophora, Hypotrichia)

The living morphology, infraciliature and morphogenesis of a new ciliate, Urosomoida paragiliformis n. sp., collected from saline soil in Weinan, China, were studied in vivo and after protargol staining. Urosomoida paragiliformis n. sp. is characterized as follows: body elongate-elliptical with no tail, flexible and slightly contractile; cortical granules dark-brown, 0.5 μm across, arranged in short irregular rows; about 33 adoral membranelles; 14 frontoventral-transverse cirri; right and left marginal rows not confluent posteriorly; two macronuclear nodules. Morphogenesis of U. paragiliformis n. sp. corresponds well with that of other Urosomoida-species except that in reorganisers the oral primordium develops membranelles that replace those at the proximal end of the old adoral zone, whereas in dividers the entire parental adoral zone of membranelles is inherited by the proter. Phylogenetic analyses based on SSU rDNA sequence data suggest a close relationship between U. paragiliformis n. sp. and Paraurosomoida indiensis. A new combination is made: Oxytrichella subtropica ( Fan et al., 2015) comb. nov. (basionym Urosomoida subtropica).