Abstract
The morphology and infraciliature of a poorly-known colepid ciliate, Pinacocoleps tesselatus (Kahl, 1930) Foissner et al., 2008, collected from brackish-water biotope (salinity 12 ‰) in Hangzhou Bay, China, were investigated using live obser-vations and silver impregnations. This species is characterized by its length of 60–85 μm in vivo, ovular shape, two ante-rior and three posterior spines, 21–25 longitudinal and 11 transverse ciliary rows on average, a macro and micro nucleus, and one terminal contractile vacuole. The key to all known seven Pinacocoleps species is updated. Additionally, we char-acterized the taxon P. tesselatus via small subunit rRNA gene data. Our phylogenetic analyses performed using both max-imum-likelihood and Bayesian methods indicate that P. tesselatus falls into the core assemblage of the family Colepidae.