Spectral composition and visual foraging in the three-spined stickleback (Gasterosteidae: Gasterosteus aculeatus L.): elucidating the role of ultraviolet wavelengths

Abstract

Visual signalling can be affected by both the intensity and spectral distribution of environmental light. In shallow aquatic habitats, the spectral range available for visually mediated behaviour, such as foraging, can reach from ultraviolet (UV) to long wavelengths in the human visible range. However, the relative importance of different wavebands in foraging behaviour is generally unknown. Here, we test how the spectral composition of ambient light influences the behaviour of three-spined sticklebacks (Gasterosteus aculeatus) when foraging for live cladoceran Daphnia magna. Although paying particular attention to the UV waveband, we measured the foraging preferences of sticklebacks for prey presented under four different spectral conditions. These conditions selectively removed UV (UV‐), short-wave (SW‐), mid-wave (MW‐) or long-wave (LW‐) light from the entire spectrum. The absence of UV and long wavelengths strongly reduced prey attractiveness for G. aculeatus compared with conditions without short-wave and mid-wave light. To control for potential light habitat preferences in the main experiment, we conducted a further choice experiment without prey stimuli. Fish in these trials did not discriminate significantly between the different spectral conditions. When comparing both experiments, it was observed that, although filter preferences for MW‐ and LW‐ conditions were virtually consistent, they differed at shorter wavelengths, with a reduced preference for UV‐ conditions and, at the same time, an increased preference for SW‐ conditions in the presence of prey. Thus, prey choice seems to be strongly affected by visual information at the short-wave end of the spectrum. The foraging preferences were also mirrored by the chromatic contrast values between prey and the experimental background, as calculated for each lighting condition using a series of physiological models on stickleback perception. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2012, 105, 359‐368.