Effect of Short Term Temperature on Physiological Body Indices of Two Estuarine Venerid Clams Katelysiaopima and Meretrixmeretrix (Mollusca: Bivalvia)

Abstract

In the present investigation, the physiological body indices like hepatopancreas index (HI), gonadal index (GI) and condition index (CI) of two estuarine clams (Katelysiaopima and Meretrixmeretrix) were estimated after exposing to three experimental temperatures (20, 25 and 35°C). In experimental design, both the clam species were exposed to selected temperatures for 192 hours (8 days) and during the exposures the body indices were determined at each 48 hours of interval. After exposing to experimental temperatures, in both the clams, all body indices like HI, GI and CI were considerably declined (p<0.001) after 192 hours of exposure. The highest decline in body indices has been noted particularly at high temperature (35°C) followed by low temperature like 20°C and 25°C. On the basis of obtained results, it confirms that, the gonadal index was closely related to hepatopancreas index and increment of condition index is directly associated with gonadal development. Relatively, M. meretrix species was more sensitive towards temperature change and it has been evident from the maximum decline in body indices than K. opima. Hence, the quantitative analysis of body indices among clams might be useful in assessing the probable effect of short-term change in water temperature on physiological process.