Abstract

Inducible defenses of prey are evolved under diverse and variable predation risks. In the co-evolution of prey and multiple predators with antagonistic selection pressures, whether inducible defense responses of prey will fall into a dilemma and its underlying mechanism are still unclear. Based on the antagonistic predation pressure from invertebrate predator Chaoborus larvae and vertebrate predator fish, we studied multi-traits and transcriptome of the freshwater crustacean Ceriodaphnia cornuta under multiple predation risks. Our results showed that Chaoborus larvae predation risks altered the expression of genes encoding cuticle protein and changed the biosynthesis of steroid hormone, cutin, suberine, and wax, promoting Ceriodaphnia to express horns and grow larger at a late development stage, whereas fish predation risks mainly triggered responses in genes encoding ribosome and pathways of unsaturated fatty acids biosynthesis, cysteine and methionine metabolism, resulting in a smaller individual size and earlier reproduction. The inducible responses on transcription and individual traits both revealed that predator unique responses are dominant and the antagonistic responses are the least. Besides, Pearson correlations between different predator unique responses are extremely weak. Furthermore, the unique individual traits triggered by different predators can be expressed simultaneously. These results indicated that Ceriodaphnia can avoid the dilemma by performing predator unique responses and diverse inducible responses are favored in the co-evolution of zooplankton and multiple predators.