Behavioral responses of Daphnia magna to stresses of chemicals with different toxic characteristics.

Behavior of an organism is affected by exposure to toxic chemicals. However, less has been known about behavioral responses of an organism to stresses of toxic chemicals with different toxic characteristics. In present work, Daphnia magna Straus was exposed to gradient concentrations of deltamethrin, chlorothalonil and nitrofen and the behavioral changes of Daphnia magna under different stress were examined. The results showed that the behavioral responses of Daphnia magna to the tested chemicals were affected in general by exposure concentration, rather than toxic characteristics of the chemicals. The duration of avoidance response (DAR) was in a power regression relationship with the toxic unit (TU), defined as the ratio of exposure concentration of the tested chemical to its LC(50-48). DAR was independent of the toxic characteristics of chemicals. However, significant behavior adjustment could be observed after exposure to deltamethrin while only step-by-step decrease in behavior strength could be observed when exposed to chlorothalonil and nitrofen. It was suggested from the observation that avoidance behaviors of Daphnia magna to exposures of chemicals with different toxic characteristics could be similar, while their specific response could be different.