Biological Diversity of Thelohanellus Kudo, 1933 (Myxozoa : Myxosporea : Bivalvulida) Parasitizing Freshwater Fishes of Indian Subcontinent

Abstract

The genus Thelohanellus Kudo, 1933 is a member of the Class Myxosporea in the Phylum Myxozoa. Spores of the genus Thelohanellus Kudo are tear-shaped, pyriform or ellipsoidal in valvular view and tear-shaped or pyriform in sutural view. Spores with spore valves are always smooth and devoid of any outgrowth. They are characterized by single pyriform or tear-shaped polar capsule with single coiled polar filament; binucleate sporoplasm mostly with polysaccharide inclusion. Members of this genus have large polysporous plasmodia with pansporoblast formation. They are histozoic parasites of freshwater fishes representing about 75 species with Thelohanellus pyriformis Thelohan, 1892 as the type species. So far, 32 species of the genus Thelohanellus are known to occur in India. In this communication, their recognition, biology and pathogenicity, if any, are summarised.