Taxonomy and molecular phylogeny of two novel ciliates, with establishment of a new genus, Pseudogastrostyla n. g. (Ciliophora, Hypotrichia, Oxytrichidae)

Abstract

Two novel hypotrichous ciliates, Pseudogastrostyla flava n. g., n. sp. and Urosomoida subtropica n. sp., isolated from Daya Bay Mangrove Park, Huizhou, southern China, were observed in vivo and after protargol staining. Pseudogastrostyla n. g. is diagnosed by having more than 18 frontal-ventral-transverse cirri, an indistinct frontoventral row, undulating membranes in Oxytricha-pattern and dorsomarginal kinety, but lacking dorsal kinety fragmentation during morphogenesis. The monotypic species, P. flava n. sp., is characterized by its brownish body colour, brown-yellowish cortical granules mostly arranged in groups, frontoventral row terminating near mid-body, and one caudal cirrus. Urosomoida subtropica n. sp. can be recognized by having one micronucleus located between two macronuclear nodules, four transverse cirri, pretransverse ventral cirrus (V/2) anteriorly located, four dorsal kineties and three caudal cirri. Phylogenetic analyses based on SSU rRNA gene sequence data indicate that Pseudogastrostyla n. g. is nested within the oxytrichids and is most closely related to Rubrioxytricha ferruginea, and that Urosomoida subtropica n. sp. clusters with Oxytricha elegans rather than the type species, U. agilis. Nodal support values are, however, too low to draw any conclusions about the molecular systematics of the genus Urosomoida.