Description of two new species of ectoparasitic Trichodina Ehrenberg, 1830 (Ciliophora: Trichodinidae) from freshwater fishes in the river Ganges, India.

Two new species of the genus Trichodina Ehrenberg, 1838, T. silondiata sp. nov. and T. pangasi sp. nov. from the gills of freshwater fish Silonia silondia (Hamilton 1822) and Pangasius pangasius (Hamilton-Buchanan) respectively from the river Ganges of West Bengal are described here. Wet smears of gills and skins were prepared in the field, air dried and impregnated with Klein's dry silver method. In case of S. silondia (Hamilton 1822) 24 out of 146 host fishes were parasitized on the gills. Infestation rate in case of P. pangasius (Hamilton-Buchanan) was not significant. From a total of 86 examined host fish, only seven were parasitized on the gills. The mean diameters of the body of the specimens of T. silondiata sp. nov. and T. pangasi sp. nov. were 32.7-60.6 (46.4 ± 6.3) μm and 38.9-54.1 (44.9 ± 3.0) μm respectively. Taxonomic and morphometric data for these ectoparasitic trichodinids based on wet silver nitrate impregnated specimens are presented.