First Report and Redescription of Thelohanellus wangi (Myxobolidae) (Kudo 1933), Infecting Gills of Cabido morar (Cyprinidae) (Hamilton, 1822) from North Bengal, West Bengal (India)

A study was performed to understand the morphology, prevalence, site of infection and histopathological changes caused by myxozoan parasites in Cabido morar from North Bengal, West Bengal, from January 2023 to December 2023. In this investigation out of 107 C. morar, 46 (43%) were infected with Thelohanellus wangi. It was found that the gills of the C. morar were infected with the species Thelohanellus wangi, which formed minute plasmodia in the gills of the host fish. The infection causes heavy mucous-laden gills. This study represents both light and scanning electron microscopic observations. Morphological and morphometrical characterization of this parasite revealed that the spores measured (17.55-21.47) µm x (9.96-12.29) µm in size. Polar capsule (10.52-13.87) µm x (8.66-9.96) µm in size and 7-8 coils in the polar filament. This paper presents the occurrence of Thelohanellus wangi in a new host and from a new locality. The intensity of infection fluctuated in different seasons, showing the highest prevalence during winter. Histological sections of infected gills show necrosis, congestion, and dilation of the gill lamellae that can cause respiratory defects.