Effect of sublethal concentrations of copper on hemocyte number in bivalves

Abstract

Seventy-five specimens of Sunetta scripta were exposed to 1, 3, and 5 ppm of Cu 2+, and sea water of 30‰ salinity, each, and 50 specimens of Villorita cyprinoides var. cochinensis to 0.15, 0.30 and 0.45 ppm of Cu 2+, and sea water of 15‰ salinity, each, for 5 days. Total hemocyte counts were made at every 24 hr. Statistical comparisons of the data indicated that total cell counts in the experimentals of S. scripta did not vary significantly from the controls at any time period. In 0.15 and 0.30 ppm Cu 2+-dosed V. cyprinoides var. cochinensis total cell counts were significantly lower than the controls at 48, 72, 96, and 120 hr, and in 0.45 ppm Cu 2+-dosed ones at all time periods. It is indicated that in the former species because the concentration range of Cu 2+ was far below the lethal dose, or because of the low uptake rate of copper in high salinity, Cu 2+ ions might not have entered the system in sufficient quantity to cause cell mortality and/or to induce the involvement of hemocytes in the transportation of Cu 2+ ions to sites of storage and excretion. On the contrary, in the latter species it is indicated that because the concentration range of Cu 2+ was close to LC 50 value, or because of the high uptake rate in low salinity, Cu 2+ ions might have entered the system in sufficient quantity to cause cell mortality and/or induce the involvement of hemocytes in the transportation of Cu 2+ ions to sites of storage and excretion, thereby effecting significant flucturations in total hemocyte counts.