Cymothoid isopods are parasitic crustaceans that cause serious impact on marine fishes, which might lead to fish mortality and economic losses. This study aims to report the histopathological changes induced by Cymothoid, Nerocila phaiopleura Bleeker, 1857 in the skin of Indian mackerel, Rastrelliger kanagurta (Cuvier, 1817). Histopathological examination of processed skin tissues showed changes caused by Nerocila phaiopleura such as skin depression, erosion of skin layers, epithelial hyperplasia, epidermal spongiosis, necrotic lesions in the muscles, oedema, muscle degeneration and fibrosis. The host response included the appearance of lymphocytes, eosinophils and macrophages. The cymothoid N. phaiopleura are serious marine fish parasites that can cause severe economic loss in the commercially important fishes. The present study represents the first record of the histopathology of parasitic cymothoid N. phaiopleura on R. kanagurta.

Parasitic cymothoid, Nerocila phaiopleura, Rastrelliger kanagurta, histopathological alterations, host response