Abstract
In the present study of Epinephelus undulosus captured in gillnets from the inshore waters of Tuticorin, Gulf of Mannar region during December 2014. The present findings represent the first occurrence of Argathona sp. and here in reported. The materials examined were deposited at the Kamaraj College, Marine Biological Research Laboratory, Tuticorin, India. The parasitological indexes were calculated. The site of attachment of the parasites on their hosts was also observed. Host-parasite relationships are considered and these parasites can cause the damage in gill, eye and internal organ including swim bladder. Marine fish parasitology is a rapidly developing field of aquatic science.