JUVENILE FRESH-WATER MUSSEL (BIVALVIA, UNIONIDAE) RESPONSES TO ACUTE TOXICITY TESTING WITH COPPER

The sensitivities of newly metamorphosed juveniles of Villosa iris and Anodonta grandis to copper were determined using 24-h static bioassay s. Two methods of assessing postexposure response were compared: direc t visual examination and the use of vital staining with neutral red. B oth species responded to copper exposures, exhibiting valve closure at concentrations as low as 24 mug Cu per liter for Villosa iris and 17 mug Cu per liter for Anodonta grandis. EC50 values of 27 mug Cu per li ter (Villosa iris) and 33 mug Cu per liter (Anodonta grandis) were cal culated on the basis of the valve closure response. Use of vital stain ing with neutral red provided an EC50 of 29 mug Cu per liter for Villo sa iris. The amber coloration of Anodonta grandis valves prevented det ermination of an EC50 using the vital staining. LC50 values of 83 mug Cu per liter (Villosa iris) and 44 mug Cu per liter (Anodonta grandis) were calculated from the results of vital staining. Neutral red was f ound to be effective in assessing postexposure mortality and sublethal responses after acute exposures to copper.