A predatory relationship between the nudibranch belonging to the Family Aeolidiidae, Aeolidiopsis sp. and a zoanthid - Palythoa mutuki was recorded from coastal waters of Veraval, Gujarat, India. This is the first record of nudibranch predation on Zoantharians along Indian waters. The Aeolidiopsis sp. of nudibranch was found alive, attached and feeding on the colonies of P. mutuki in coastal waters. Observations in controlled environment also revealed metabolic dependence of the nudibranch on the host. The nudibranch was seen completing its life cycle in the host, as its eggs were observed, laid in concentric ring pattern and the presence of the juveniles. These observations and the existing knowledge of them harbouring zooxanthellae make the Aeolidiopsis sp. to be categorised as a
facultative ectoparasite instead of a predator. 

Predation, parasitism, ectoparasite, nudibranch, zoanthid