Abstract
This paper investigates the morphology, infraciliature and small-subunit (SSU) rRNA gene sequences of two hypotrichous ciliates, Neourostylopsis orientalis n. sp., and Protogastrostyla sterkii (Wallengren, 1900) n. comb. (basionym Gastrostyla sterkii), collected from coastal waters in southern China. Neourostylopsis orientalis n. sp. is diagnosed mainly by the arrangement of brownish cortical granules, the numbers of adoral membranelles and frontal and transverse cirri and the characteristics of its midventral cirral pairs. The SSU rRNA gene phylogeny strongly supports the establishment of the new genus Neourostylopsis n. gen., which is characterized mainly by the following features: frontal and transverse cirri clearly differentiated, buccal cirri present, two frontoterminal cirri, midventral complex composed of midventral pairs only and not exceeding the halfway point of the cell, more than one row of marginal cirri on each side which derive from individual anlagen within each parental row, caudal cirri lacking. Thus, two new combinations are required: Neourostylopsis songi (Lei et al., 2005) n. comb., and Neourostylopsis flavicana (Wang et al., 2011) n. comb. Additionally, improved diagnoses for both Metaurostylopsis and Apourostylopsis are supplied in this study. Protogastrostyla sterkii (Wallengren, 1900) n. comb. differs from the similar congener Protogastrostyla pulchra mainly in body shape, ratio of buccal field to body length in vivo and molecular data. Based on the present studies, we conclude that the estuarine population of P. pulchra collected by J. Gong and others [Gong et al., J Eukaryot Microbiol (2007) 54, 468-478] is a population of P. sterkii.