Effect of Subacute Concentration of Cadmium on the Energetics of Freshwater Mussel Lamellidens marginalis (LAM.)and Fish Labeo rohita (HAM.)

The levels of pyruvate and lactate, and the activities of succinate dehydrogenase (SDH) and lactate dehydrogenase (LDH) were estimated in the organs of freshwater mussel Lamellidens marginalis and fish Labeo rohita at days 10, 20 and 30 after exposure to the subacute (0.7 mg/L) concentration of cadmium. A decrease was observed in succinate dehydrogenase (SDH) activity along with a corresponding decrease in pyruvate level with an increase in lactate dehydrogenase (LDH) activity and lactate level in ctenidium, mantle, hepatopancreas and foot of the mussel and in the kidney, liver and muscle of the fish at all the days of exposure. Interestingly, an increase was observed in SDH activity and pyruvate level with a decrease in LDH activity and lactate levels in the gills of the fish. Among the exposure periods, either the percent suppression or elevation progressively recovered and reached to near normal over time of exposure in the order: day 10>20>30 in the organs of mussel. Whereas, in the organs of fish it was in the order: day 10>20<30. Thus, between the two groups of animals, either the percent suppression or elevation was progressively recovered over time of exposure in the organs of mussel, but the fish exhibited a little recovery at day 20 with a significant fall at day 30. These results indicated an adaptive ability to subacute concentration of cadmium in the organs of mussel by normalizing the oxidative and glycolytic pathways on prolonged exposure; whereas the fish exhibited susceptibility due to the suppression of oxidative metabolism and increased dependency on anaerobic glycolysis.