The morphological and life-history data of two Daphnia species under different fish kairomone concentrations

Daphnia species can avoid predation by sensing fish kairomones and producing inducible defenses by altering the phenotype. However, the inducible response mechanisms of different Daphnia species to fish kairomones remain unclear. In this study, the morphological and life history strategy of two Daphnia species (Daphnia pulex and Daphnia sinensis) exposed to Aristichthys nobilis kairomones were studied. In the presence of fish kairomones, the two Daphnia species exhibited significantly smaller body length at maturity, smaller body length of offspring at the 10th instar, and longer relative tail spine of offspring. Nevertheless, other morphological and life history traits of the two Daphnia species differed. D. pulex showed a significantly longer relative tail spine length and shorter age at maturity after exposure to fish kairomones. The total offspring number of D. sinensis exposed to fish kairomones was significantly higher than that of the control group, whereas that of D. pulex was significantly lower. These results suggest that the inducible mechanisms (e.g., relative tail spine length, age at maturity, and total offspring number) of the two Daphnia species exposed to fish kairomones differ significantly and that the maternal morphological traits can be transferred to the offspring such that they can avoid predation.