Mesocosm experiments validate induction of Daphnia vertical migration by the fish-derived kairomone 5α-cyprinol sulfate

The fish-borne bile salt 5α-cyprinol sulfate (CPS) has been identified as a kairomone inducing the predator avoidance behavior “diel vertical migration” (DVM) in Daphnia magna in response to fish. Conclusions about the ecological significance of CPS have been derived from laboratory experiments only. Using a mesocosm approach, we investigate whether the role of CPS as a kairomone can be confirmed in the field. We demonstrate that CPS induces downward migration during daytime in a field-derived Daphnia community consisting of D. longispina and D. cucullata and in D. longispina in particular. In the study lake, D. longispina shows a similar pattern of DVM. Quantification of CPS by HPLC-MS confirms that CPS in situ concentrations in the lake are sufficiently high for induction of daytime downward migration of D. longispina in this oligo-mesotrophic lake. Conclusively, we provide evidence for the significance of CPS as a kairomone in freshwater systems.