Lingyun Chen

The morphology and morphogenesis of two populations of the soil hypotrichous ciliate, Parakahliella macrostoma (Foissner, 1982) Berger et al. 1985, isolated from northwest China, were investigated based on specimens examined in vivo and stained with protargol. Our populations resemble the original one in terms of their live characters and cirral pattern. The main events during binary fission are as follows: (1) the parental adoral zone of membranelles is retained completely by the proter; (2) both in the proter and in the opisthe five frontal-ventral cirral anlagen are recognizable; (3) the marginal rows and dorsal kineties develop intrakinetally. In addition, the SSU rRNA gene was sequenced for the genus Parakahliella for the first time. Molecular phylogenetic analyses suggest that two populations of the genus Parakahliella cluster together and have a close relationship with species of Oxytrichidae. 

Tachysoma pellionellum Stokes, 1887, a freshwater ciliate isolated from Stone Mountain State Park, North Carolina, was studied in vivo and after staining with protargol. The population was characterized mainly by having the typical 18 frontal-ventral-transverse cirri; posterior ends of left and right marginal rows not confluent; five dorsal kineties and one dorsomarginal kinety; two macronuclear nodules near left cell margin with one or two micronuclei between them; contractile vacuole located at mid-body near left margin. Morphogenesis is characterized as follows: (1) in the proter, the parental adoral zone of membranelles is retained completely; (2) 18 frontal-ventral-transverse cirri are derived from the anlage of the undulating membrane and the five streaks of the frontal-ventral-transverse anlagen; (3) marginal rows develop intrakinetally; (4) anlagen of dorsal kineties 1, 2 and 4 develop in the parental structure and anlagen of dorsal kineties 2 and 4 fragment in the posterior region forming anlagen of dorsal kineties 3 and 5; (5) only one dorsomarginal kinety formed; (6) the two macronuclear nodules fuse into a single mass, which then divides. Phylogenetic analyses based on sequences of the gene coding for SSU RNA revealed a close relationship between T. pellionellum and the Oxytricha clade, both of which grouped with Kleinstyla dorsicirrata and Heterourosomoida lanceolata.