UTTAR PRADESH JOURNAL OF ZOOLOGY

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.