Morphology and Phylogeny of Three Pseudovorticella Species (Ciliophora: Peritrichia) from Brackish Waters of China.

Abstract

The biodiversity of peritrich ciliates from brackish biotopes is rarely investigated, especially members of the genus Pseudovorticella. Here, the morphology of three species of Pseudovorticella, i.e. P. cf. vestita (Stokes, 1883) Jankowski, 1976, P.spathulata sp. n., and P.qinghaiensis sp. n. isolated from brackish waters were studied. Pseudovorticella cf. vestita is characterized by inverted bell-shaped cell; a J-shaped macronucleus; a single contractile vacuole ventrally located; P3 three-rowed; pellicle striated with highly developed pellicular vesicles; 18-22 transverse silverlines between peristome and aboral trochal band, and 9-13 between aboral trochal band and scopula. Pseudovorticella spathulata sp. n. differs from its congeners by the following combination of characters: elongate-elliptical cell; a single contractile vacuole near ventral wall of infundibulum; a J-shaped macronucleus; P3 three-rowed; 24-34 silverlines between oral area and aboral trochal band and 6-10 between aboral trochal band and scopula. Pseudovorticella qinghaiensis sp. n. is characterized by: cell with an oval outline; a single contractile vacuole near ventral wall of infundibulum; a C-shaped macronucleus; P3 three-rowed; 30-35 and 9-11 transverse silverlines above and below the trochal band, respectively. The SSU rDNA sequences of five Pseudovorticella species, namely P.annulata, P.monilata, P.parakenti, P.spathulata sp. n., and P. cf. vestita, plus that of Zoothamnium hartwigi, are reported for the first time and their evolutionary relationships are investigated. Five undefined Pseudovorticella forms are considered might be conspecific with P.monilata. Two congeners are conspecific with P.spathulata sp. n. Phylogenetic analyses based on SSU rDNA sequences reveal that Pseudovorticella is not monophyletic and Z.hartwigi clusters with its congeners as expected.