Predator-induced escape response in Daphnia

We studied the effects of predator exudates on evasion efficiency in two Daphnia magna clones that differed in their sensitivity to the kairomones. Pre-expo- sure to kairomones significantly increased the chances of survival of sensitive Daphnia when confronted with actively-foraging invertebrate and vertebrate predators, as com- pared to individuals which had not been pre-exposed to predator chemical cues. The induced response is adaptive: predators foraging on a mixture of sensitized and non- sensitized individuals, first removed those which had not been pre-exposed, or were non-sensitive to predator exudates. Predator-induced escape responses, therefore, can be a target for selection.