A limited role for ultraviolet radiation when threespine sticklebacks (Gasterosteus aculeatus) prey upon Daphnia
Any trait of predatory species that enhances hunting efficiency should be favoured by natural selection. Foraging in threespine sticklebacks (Gasterosteus aculeatus) is mainly visually mediated. The visual system of sticklebacks is extended into the ultraviolet (UV) range of the spectrum. We tested, in four different experimental setups, the influence of different spectral compositions, in particular the presence and absence of ultraviolet wavelengths, on the feeding performance of threespine sticklebacks while foraging on live Daphnia magna, which absorb UV. In the three experiments with similar background reflections, the foraging behaviour of sticklebacks was unaffected by removing UV wavelengths. But in the fourth experiment, sticklebacks showed a significant difference between the rate of detecting prey against a UV-reflecting or UV-absorbing background. Sticklebacks significantly attacked prey faster when the background lacked UV reflections. Thus, the interaction of prey with its background in UV wavelengths influenced sticklebacks' prey detection. Removing long wavelengths impaired foraging rate, suggesting that long wavelengths may be more important in foraging tasks than UV wavelengths.