Prevalence of a protozoan parasite Cristigera sp. (Ciliophora:Ciliatea) from edible oysters (Mollusca:Bivalvia) of Sundarbans, West Bengal, India.

The coastal region of West Bengal is bestowed with a wide range of natural forest and aquatic resources. The estuarine complex is a culmination of the interaction of land, sea and freshwater. It offers diverse specialised habitats such as mangroves, non vegetated mudflats, inter tidal zones and reclaimed areas. Such areas are home to a number of terrestrial, freshwater and marine communities. Edible oyster resources in these regions are Crassostrea gryphoides and Saccostrea cucullata, which are the keystone species found in the intertidal zone and can tolerate huge variation of salinity. These are used as food by local people and marketed to earn cash. The population of this species has been declined due to parasitic infection and pollution. There are many protozoan parasites which infect these oysters causing diseases. During survey period, a protozoan parasite of the genus Cristigera have been observed only from the edible oyster Crassostrea gryphoides collected from Kaikhali and Frasergunj among three selected sites namely Kaikhali, Frasergunj and Digha of West Bengal mainly during monsoon and post-monsoon season. Considering such rare and specific prevalence of Cristigera sp, it may be considered as potential bio-indicator.