Effects of cadmium and body mass on two anti-predator behaviors of five species of crayfish

Five crayfish species (Orconectes placidus, O. virilis, Procambarus acutus, P. alleni and P. clarkii) were subjected to Cd exposure in 96 h acute toxicity tests to assess changes in two anti-predator behaviors, the tail-flip response and the claw-raise response. The tail-flip response was significantly affected by Cd exposure in three of five cases (ANOVA p<0.05). In three species, planned comparisons with Duncan's Test revealed that at least one exposure concentration of Cd decreased the frequency of the tail-flip behavior significantly compared to controls (p<0.05). The lowest level of Cd to significantly impair the tail flip response was 0.306 mg Cd L^_1 for O. virilis. Regression analysis detected significant decreasing trends in the tail-flip behavior as cadmium concentrations increased in four species of crayfish (p<0.05, r>0.42). In two cases, planned comparisons with Duncan's test revealed that at least one exposure concentration of Cd increased the frequency of the claw-raise response significantly compared to controls (p<0.05). The lowest level of Cd to significantly increase the claw raise response was 3.50 mg CdL^-1 for P. clarkii. Regression analysis indicated that the claw-raise behavior was related to Cd concentration in two species (p<0.05, r>0.50). When control groups were compared across species, a significant correlation was measured between body mass and both the tail flip and claw raise behaviors. Across the five species, as body mass increased, the tail flip response decreased in frequency (r = -0.72;p<0.001) and the claw raise response increased in frequency (r = 0.70; p = 0.001). Interference with either behavior, but especially the tail flip response, could have important survival consequences, especially for juvenile crayfish which are typically more sensitive to cadmium exposure.