Molecular studies reveal host plasticity and wide geographical distribution of Myxobolus linzhiensis Li et al. 2017 and Thelohanellus wangi Yuan et al. 2015.

Myxozoans, the major microscopic metazoan parasites of fish, can cause great economic loss in the fishery industry. In the search for myxozoan diversity during 2016-2018 in the western part (Bankura and Purulia district) of West Bengal, freshwater fishes were examined. Plasmodia with numerous spores of parasites were found in gills. Light microscopic studies revealed spore morphometry. Molecular taxonomic studies were done with 18S rRNA gene sequencing. The primers were UEP-F, UEP-R, MX5 and MX3. Collected myxozoans have been identified as Myxobolus linzhiensis Li et al. 2017 (MK412936) and Thelohanellus wangi Yuan et al. 2015 (MK412938), after comparing with other closely related spores and sequenced data from GenBank. M. linzhiensis has been collected from the gills of Labeo rohita at Purulia. The type specimen was reported from the gills of Schizothorax oconnori in China. T. wangi was collected from the gills of Catla catla from Bankura. The type specimen was reported from the gill filament of Carassius auratus gibelio from China. The western part of West Bengal; i.e., Bankura and Purulia districts are very hot and dry (oriental realm), rather than Wuxi and Wuhan of China (Palearctic realm). Phylogenetic relationships conclude that two studied parasites Myxobolus linzhiensis Li et al. 2017 and Thelohanellus wangi Yuan et al. 2015 of Palearctic host fishes have also been recorded from different host fishes of the oriental realm. These interesting features of the studied species, host plasticity and wide geographical distribution, are reported here for the first time.