Host-parasite relation between Bucephalopsis haemeanas and Crassostrea madrasensis in the Pulicat Lake

Abstract

A digenic trematode Bricepltnlopsis Itne~nenrtnws as observed in the gonads of the backwater oyster Crassos~rearnndrnseisofth e Pulicat Lake. Maximum vercenta-n eof infection was 17.7 durine-D ecember. Highest inc~dence of infection was observed in the size groups of 60-69 mm and 100-109 mm. Initially the infection was noticed in the gonads of the oyster andlater it was found to invade the other tissues such as mantle, gill and digestive gland. Infection was found to be more in the partly spent and spent indiv~duals than in the fully ripe and individuals with gametogenic activity. As a result of infection, gametes are resorbed quickly and thus oysters are castrated leading to indeterminate stage. In the majority of parasitised oysters, feed~ngw as noted to be very poor. The infection seems to be seasonal and starts when the sallnity and tem2erature in lake decline considerably after the heavy rains of North-East Monsoon. The parasites were observed to die at the salinity below 2.3%,.