Haemolymph protein levels in copper-stressed bivalves

Abstract

Haemolymph protein levels were studied in two clam species, Sunetta scripta and ViIlorita cyprinoides var. cochinensis exposed to three sublethal concentrations of copper. One hundred specimens of S. scripta were exposed to each of the three concentrations of copper, 1, 3, and 5 ppm. The control group consisted of 75 specimens maintained in clean waters. Fifty specimens of V. cyprinoides var. cochinensis were exposed to each of the three concentrations of copper, 0.15, 0.30 and 0.45 ppm, and 50 specimens served as the controls. The sublethal concentrations were chosen after LC 50 studies. Protein levels were estimated every 24 h up to 120 h in both the cases. The results indicated that haemolymph protein levels in S. scripta exposed to 1 ppm copper were significantly lower at 48, 72, 96, and 120 h, and in those exposed to 3 ppm at 120 h than the control values. Those exposed to 5 ppm of copper, interestingly, did not show any significant difference in protein levels at any time-period when compared with the controls. Specimens of V. cyprinoides var. cochinensis exposed to 0.15 ppm of copper showed significantly lower levels than the controls at 24, 48, 72, 96, and 120 h, and those exposed to the other two concentrations of copper at 48, 72, and 96 h. It is indicated that protein level in the haemolymph compartment in copper-stressed condition is at a metabolic state of balance between entry and exit of protein into and out of the haemolymph compartment. While seepage of cytosol protein into the haemolymph compartment resulting from the destabilization of cell membranes constitutes entry, binding of protein with the metal ions resulting in denaturation and eventuai removal from the haemolymph, and degradation of proteins into amino acids for the maintenance of osmotic balance achieved by the use of a compatible solute system involving amino acids along with other solutes comprise the exit.