First record of Gnathia sp. an ectoparasitic isopod isolated from the coral reef fish, Heniochus acuminatus collected from the Gulf of Mannar region, southeast coast of India.

An ectoparasitic isopod, Gnathia sp. was found in the Gill chambers of Heniochus acuminatus collected from the Gulf of Mannar region, Southeast coast of India. The present study signifies the new record of Gnathia sp. an coral reef ectoparasitic isopod captured from the gill net during October 2014. Among the 36 specimens examined 5 specimens were infested with Pranzia larvae of Gnathia sp. The size of the isopods were ranged from 1.5 to 3.2 mm and the host fish length varied between 119 and 230 mm. They were specifically found attached to the gill chambers and no damage observed in the lamellar pattern.