Predation Risk Perception in Daphnia carinata Induced by the Milt of Common Carp (Cyprinus carpio)

Numerous experimental studies suggest that many organisms can sense predation risk and subsequently adjust their life history, behavior, and morphology as adaptations to predators. The aim of the present study was to test if fish milt would induce changes in Daphnia carinata. We exposed D. carinata to the milt of fish and then measured parameters of growth and reproduction until the offspring of the third clutch were released. Individual growth rate was higher in the treatment with fish milt than in the control. Size at the first three clutches was greater in the milt treatment than in the control. Age at the first three clutches was significantly younger in the high milt treatment than in the control. Moreover, D. carinata produced more offspring in the presence of fish milt The degree of response by D carinata was dose-dependent, correlating with the concentration of milt. D carinata can use some substance originating from fish milt to sense risk of predation risk and change its life history to increase its fitness.