Morphology, morphogenesis and molecular phylogeny of a novel soil ciliate, Pseudouroleptus plestiensis n. sp. (Ciliophora, Oxytrichidae), from the uplands of Colfiorito, Italy

The terrestrial oxytrichid ciliate Pseudouroleptus plestiensis n. sp., isolated from soil samples collected from the uplands of Colfiorito (Umbria region, Italy), was investigated using live observation and protargol impregnation. The morphology, morphogenesis and molecular phylogeny inferred from small-subunit (SSU) rRNA gene sequences were studied. The novel species is mainly characterized by the following: a cell size of about 145×35 µm in vivo; two ellipsoidal macronuclear nodules and two to four micronuclei; adoral zone about 26% of body length with a mean of 30 membranelles; about 40 cirri in the right marginal row and 38 in the left marginal row; left fronto-ventral row consisting of about 27-40 cirri, right fronto-ventral row of about three to seven cirri forming a short row to the right of the rear portion of the left fronto-ventral row; one parabuccal cirrus ( = III/2), one buccal and one post-peristomial cirrus; and four dorsal kineties with caudal cirri at the end of kineties 1 and 2. The morphogenesis of the novel species is similar to that of Pseudouroleptus caudatus. Phylogenetic analyses based on SSU rRNA gene sequences consistently placed the novel species within the family Oxytrichidae Ehrenberg, 1838, clustering with P. caudatus and the genus Strongylidium. The results from the present study contribute to the expanding knowledge of the diversity of ciliates in Italian soil.