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Free keywords:
behavior; chemical communication; Cladocera; Daphnia; diel vertical migration; kairomone; predator avoidance; zooplankton
Abstract:
Planktivorous fish release a cue of an unknown chemical nature into the water that induces diel vertical migration in Daphnia as predator avoidance response. We used a bioassay to obtain information about the chemical nature of the kairomone. We present a method to enrich the cue from holding water of fish by sorbent extraction. The kairomone exuded by Leucaspius delineatus can be characterized as a nonolefinic low-molecular-weight anion of intermediate lipophilicity. The presence of amino groups in the molecule can be excluded, whereas hydroxy groups are essential for activity. Separation by HPLC yielded only one active fraction. The kairomones released by Carassius carassius and Rutilus rutilus showed the same chemical characteristics, suggesting that the kairomones from different species of fish, sensed by Daphia, are very similar, if not identical
