Redescription of two little-known urostyloid ciliates, Anteholosticha randani ( Grolière, 1975) Berger, 2003 and A. antecirrata Berger, 2006 (Ciliophora, Urostylida)

The morphology of two little-known urostyloid ciliates, Anteholosticha randani ( Grolière, 1975) Berger, 2003 and A. antecirrata Berger, 2006, collected from freshwater biotopes in southern China, was studied based on live observations and protargol staining. Anteholosticha randani is characterized by its bipartite adoral zone and short, longitudinally aligned undulating membranes. One early stage of reorganization/morphogenesis, one early-middle stage of reorganization and one middle stage of morphogenesis are also reported. Anteholosticha antecirrata is characterized by its large body size in vivo (200–400 × 40–80 μm), a row of buccal cirri and conspicuous, yellow-green cortical granules. Phylogenetic analyses based on SSU rDNA sequence data reveal that A. antecirrata may share a most recent common ancestor with Urostyla grandis and Bakuella granulifera, whereas A. randani branches independently and is sister to a large clade that includes Pseudourostyla, Pseudokeronopsis, Caudiholosticha and several species of Anteholosticha.