Influence of lighting environment on social preferences in sticklebacks from two different photic habitats. I. mate preferences of wild-caught females

Abstract

Ultraviolet A (UVA) signals (320-400 nm) are important in mate choice in numerous species. The sensitivity for ultraviolet signals is not only assumed to be costly, but also expected to be a function of the prevailing ecological conditions. Generally, those signals are favored by selection that efficiently reach the receiver. A decisive factor for color signaling is the lighting environment, especially in aquatic habitats, as the visibility of signals, and thus costs and benefits, are instantaneously influenced by it. Although ecological aspects of color signal evolution are relatively well-studied, there is little data on specific effects of environmental UV-light conditions on signaling at these shorter wavelengths. We studied wild-caught gravid female three-spined sticklebacks Gasterosteus aculeatus of two photic habitat types (tea-stained and clear-water lakes), possessing great variation in their UV transmission. In two treatments, tea-stained and clear-water, preferences for males viewed under UV-present and UV-absent conditions were tested. A preference for males under UV-present conditions was found for females from both habitat types, thus stressing the significance of UV signals in stickleback´s mate choice decisions. However, females from both habitat types showed the most pronounced preferences for males under UV-present conditions under clear-water test conditions. Moreover, reflectance measurements revealed that the carotenoid-based orange-red breeding coloration in wild-caught males of both habitat types differed significantly in color intensity (higher in clear-water males) and hue (more red shifted in clear-water males) while no significant differences in UV coloration were found. The differential reflection patterns in longer wavelengths suggest that sticklebacks of both habitat types have adapted to the respective water conditions. Adaptations of UV signals in a sexual context to ambient light conditions in both behavior and coloration seem less evident.

Influence of lighting environment on social preferences in sticklebacks from two different photic habitats. II. Shoaling and mate preferences of lab-bred fishes

“…The preferences of lab-bred F1 sticklebacks from both clear-water and tea-stained habitats during UV-based female-mate preference, which we tested in the present study, were largely similar to those of wild-caught females ( Hiermes et al 2021 ): an overall preference for males under UV-present conditions in the clear-water treatment ( Figure 4A, B , Table 2 , and Supplementary Table S2 ). This result points to a genetic influence on UV mate preferences.…”

“…Thus, water color during the testing of preferences affected UV-based female preference of fish from tea-stained lakes even after being raised under full light spectrum conditions in clear water. In the wild-caught females ( Hiermes et al 2021 ), there were no significant water-color treatment effects as the females from both habitat types tended to prefer males under UV-present conditions in both water-color treatments. There thus may be differences in UV-preferences in the tea-stained treatment between wild-caught and F1 females that may point to an effect of developmental plasticity.…”

“…After both male and female were located in separated plastic boxes, the Petri-dish with the nest was gently taken from the male’s aquarium and placed at the back wall of the male compartment (see Figure 2B ). Afterward the female was introduced into the tank and the experimental procedure described above (see shoal and habitat preference) followed (details in Hiermes et al 2021 ). Thus, test fish were tested in clear- and tea-stained water, acclimatization and observation periods were 15 min, and fish were tested twice in each water-color treatment with filters exchange after the first acclimatization and observation period.…”

“…In detail, test fish had the choice between a shoal or a reproductively active male, respectively, viewed under UV-present and UV-absent conditions, and were tested in 2 water-color treatments (tea-stained and clear-water), which matched lighting conditions in the habitats of origin. The results are compared with data from similar experiments conducted with wild-caught fish from the same study populations ( Hiermes et al 2015 , 2021 ). We would expect comparable UV-preference patterns of wild-caught and lab-bred fish when there exist genetic influences on UV preferences.…”

The sensory impacts of climate change: bathymetric shifts and visually mediated interactions in aquatic species

“…However, even over evolutionary timescales, fish do not always alter their signal colouration when faced with changes in light environment. For example, Hiermes et al [55] examined sticklebacks that have inhabited 'tea-stained' lakes in Scotland, which heavily absorb UV wavelengths, for more than 10 000 generations. They found that despite the low transmission of UV wavelengths in this habitat, males in tea-stained lakes still reflect UV light when reproductively active, and female sticklebacks still preferred males with UV reflectance.…”