5α-cyprinol sulfate, a bile salt from fish, induces diel vertical migration in Daphnia

Prey are under selection to minimize predation losses. In aquatic environments many prey use chemical cues released by predators, which initiate predator-avoidance. A prominent example of behavioural predator-avoidance constitutes diel vertical migration (DVM) in the freshwater microcrustacean Daphnia spp., which is induced by chemical cues (kairomones) released by planktivorous fish. In a bioassay-guided approach using liquid chromatography and mass spectrometry we isolated the kairomone from fish incubation water and identified it as 5α-cyprinol sulfate inducing DVM in Daphnia at picomolar concentrations. The role of 5α-cyprinol sulfate in lipid digestion in fish explains why from an evolutionary perspective fish has not stopped releasing 5α-cyprinol sulfate despite the disadvantages for the releaser. The identification of the DVM-inducing kairomone enables investigating its spatial and temporal distribution and the underlying molecular mechanism of its perception. Furthermore, it all...