Abstract
Members of the genus Thuricola are a highly specialized group of peritrichous ciliates possessing a protective barrel-shaped lorica. The genus presents many difficulties in terms of species separation and definition, and in this context the present study investigates three species by protargol staining and analyses of SSU rDNA sequences. Based on their morphologic characteristics and biotope, they were identified as three poorly known forms in Thuricola, namely T. obconica Kahl, 1933, T. kellicottiana (Stokes, 1887) Kahl 1935 and T. folliculata Kent, 1881, respectively. T. obconica is characterized by possessing curved lorica and a single valve in vivo. T. kellicottiana is distinguished by two valves with a spine on the main valve, and a generally long internal stalk upon which the zooids sit. T. folliculata also has two valves but lacks a spine. The ciliature of the three species are basically similar. The main features are characterized as follows: infundibular polykineties 1-3 (P1-3) are relatively long and composed of three rows each; P1 bends twice and comprises three equally long rows; P2 ends near the second bend of P1 with all rows exhibiting a staggered arrangement; P3 converges with P1 at adstomal end, its row 1 at least twice as long as the other two rows; epistomial membranes 1 and 2 are present. Silverline system in Vorticella-pattern. Phylogenetic analyses indicate that the three ciliates in this study cluster together within one of the two major sub-clades within the Vaginicolidae.