Parastrombidinopsis shimi n. gen., n. sp (Ciliophora : Choreotrichia) from the coastal waters of Korea: Morphology and small subunit ribosomal DNA sequence

Abstract

The planktonic ciliate parastrombidinopsis shimi n gen., n sp is described from both living cells and quantitative protargol-stained (QPS) preperations and the sequence of the small subunit rDNA (SSU rDNA) is reported. This species is almost oval when the cells are alive; when stained, it is cylindrical for the upper two-fifths, half-bowl shaped for the middle two fifths, and narrow rod-shaped for the lower one-fifth. The ranges (and mean +/- standard deviation, n = 20) of cell length, cell width, and the oral diameter of living cells were 112-221 mu m (168 +/- 39), 88 - 176 mu m (121 +/- 30), and 53 - 110 mu m (80 +/- 14), respectively, while those of the QPS-stained specimens (n = 54) were 88 - 225 mu m (162 +/- 29), 55 - 163 mu m (102 +/- 19), and 53 - 98 mu m (69 +/- 9) respectively. Thirty-six to 48 external oral polykinetids had cilia 25 - 40 mu m long. However, unlike Strombidinopsis species sensu stricto, P. shimi has an external oral polykineted zone that is an open circle. This species in the subclass has two shorter polykinetids associated with the end of the oral polykinetid zone, deep in the oral cavity. Like Strombidiopsis species in the posterior regions with 68 - 105 dikinetids per kinety. Both kinetocomes of each kinetid bore cilia 3 - 10 mu m long parastrombidinopsis shimi had 2 (1 - 4) ovoid macronucleus of 20 - 82 x 15 - 32 mu m. When properly aligned, the sequence of the SSU rDNA of P shimi (GenBank Accession No AJ786648) was approximately 5% different from that of Strobilidium caudatum as a new species in a new genus belonging to the family Strombidinopsidae.