The effect of parthenogenic eggs in Daphnia magna on prey location by the bluegill sunfish (Lepomis macrochirus)

The distance at which the bluegill sunfish (Lepomis macrochirus) can locate Daphnia magna with parthenogenic eggs is shown to be significantly greater than the reactive distance for non-gravid Daphnia of the same size. This difference is due to greater visibility of the gravid prey and not to different locomotor behavior, since there was no correlation between the number of eggs carried by a Daphnia and the antennal beat frequency. Based on this experiment and other observations, an explanation is given for selective predation of polymorphic cladoceran populations.