Molecular phylogenetics reveals a species complex pattern of closely related members of genus Thelohanellus (Cnidaria: Myxosporea) from the Indian subcontinent.

Out of the total 2600 myxozoan species reported so far, Thelohanellus Kudo, 1933 is the second most prevalent genus comprising of about 150 species after Myxobolus Butschli, 1882 infecting both freshwater and marine fishes. In general, these are mostly histozoic (within the tissues) and sometimes coelozoic (in body cavities). The present paper deals with the study of a novel Thelohanelloid T. neocyprini infecting gills of Catla catla and species complex among the member species of Thelohanellus genus from the Indian subcontinent infecting gills, fins and muscles. The species forming species complex are T. rohitae, T. catlae, T. jiroveci, T. seni, T. bifurcata, T. dykovae, T. neocyprini, T. filli, T. muscularis and T. theinensis. The phylogenetic analysis was also done on the basis of 18S rDNA. The homogeneity was found to be between 90 and 99%. The factors responsible for the species complex could be phylogeography, host reluctant, organ and tissue specificity of the these myxozoan parasites. Study of more genetic markers facilitated with morphotaxonomy can be used to sort out the occurrence of species complex among the morphologically different species having similar genetic makeup and vice-versa.
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