MODULATION IN RESPIRATORY DYNAMICS OF THE ESTUARINE CLAM, Katelysia opima (Gmelin) UNDER SUBLETHAL AND LETHAL STRESS OF CADMIUM CHLORIDE

The present study was conducted to find out effect of lethal and sublethal concentrations of CdCl2, 2½ H2O for 96 hrs. Static Bioassay Tests were conducted to find out LC0 and LC50 values for summer, monsoon and winter of 2018/19. The data was analyzed by Finney’s probit chart analysis method to calculate LC50 and 95% lower and upper fiducial limits. These predetermined values for cadmium chloride concentrations were used for exposure to LC0 and LC50 group of clams. Experiments were conducted during summer, monsoon and winter by maintaining control group of clams. Estuarine water parameters like temperature, pH, salinity, rainfall and oxygen saturation were recorded. In the present study, it was found that, cadmium chloride has significant influence on rate of oxygen consumption. During summer, clams from LC0 and LC50 group were treated with 0.8 and 1.3 ppm cadmium chloride, while in monsoon these values were 1.1 and 1.6 ppm respectively. During winter, clams from LC0 and LC50 group were exposed to 1.0 and 1.8 ppm cadmium chloride respectively. These differences in subletal and lethal concentrations were attributed to seasonal estuarine water parameters. Clams from control group consumed more oxygen in winter and less in monsoon. During summer, clams from LC0 group showed 3.01, 2.14, 4.98 and 7.64% significant increase at the end of 12, 24, 36 and 48 hrs respectively. Clams showed significant decrease up to the end of 96 hrs. Clams from LC50 group showed 3.61 and 6.0% increase at the end of 12 and 24 hrs, After 36 h, clams exhibited significant decrease in oxygen uptake. Moreover similar pattern of oxygen consumption was observed in winter. During monsoon clams from LC0 group showed significant increase at the end of 12, 24, 36 and 48 h and further decrease up to end of 96 hrs. Clams from LC50 group showed 0.98% non-significant increase at the end of 24 hrs, while significant decrease at the end of 12, 36, 48, 60, 72 and 96 hrs. In the present study it was found that changes in oxygen consumption in clams from control group were attributed to highly labile estuarine water parameters and breeding season of clams, while, alterations in oxygen consumption of LC0 and LC50 group are moreover attributed to cadmium chloride stress.