Simultaneous double parasitism by the parasitic cymothoids (Crustacea: Isopoda) of two genera on a single host fish Tenualosa toli from India

Abstract Members of the fish parasitic isopod family Cymothoidae usually parasitize a host fish by a single species infestation. For the first time from Indian waters two species of cymothoids, the body surface infesting Anilocra grandmaae Aneesh, Hadfield, Smit and Kumar, 2021 and the branchial infesting Agarna malayi Tiwari, 1952, were reported simultaneously parasitizing the same individual toli shad, Tenualosa toli (Valenciennes, 1847). Each double-infested T. toli harboured an ovigerous female of A. grandmaae and an ovigerous female and male of A. malayi. Out of 814 host fishes collected from seven different localities, along the Kerala coast, southwest coast and Bay of Bengal coast, 113 fishes were infested with only A. malayi and 71 individuals were infested with only A. grandmaae. Interestingly, nine individuals of T. toli harboured both A. malayi and A. grandmaae simultaneously. Cymothoid co-occurrence is rarely reported, and this is the first report of two cymothoid species infesting a single fish host from India. Globally, it is the third record of simultaneous occurrence of two cymothoids and the first record of body surface and branchial cymothoids parasitising the same individual fish.