THERMAL RESPONSE TO PROSOBRANCH SNAILS AT DESERT REGION OF RAJASTHAN (NORTH INDIA)

Thermal tolerance of prosobranch snails namely pond Bellamyabengalensis, Gabbiaorcula and Digoniostoma pulchella were studied in freshwater ponds namely Gajner and Kodemdesar pond situated near Bikaner, Rajasthan (Indian desert) as well as under laboratory conditions. Prosobranch snails were more sensitive to low temperature. The absolute lethal temperature for B. bengalensis, G. orcula and D. pulchella was noted as 100C, 50C and 150C or less respectively, while these could survive at higher range of even 450C, though under stress. None of prosobranch snail was found to be active below 50C and above 450C. In field also the population was reduced close to nil in January extremely low and extremely high during June; when water temp. was noted as 160C and 380C respectively during the study hours. However, the minimum and maximum temperatures over diurnal cycle during these months are expected to be still more extreme as evident from meteorological records of the region.