How seeing 'red' is correlated to herbivory: from genes to behaviour

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Coral reefs, especially the world famous Great Barrier Reef, are one of the most diverse and colourful habitats on our planet, and many marine organisms use colour vision to find food, recognize mates and foes, or compete for resources. At the core of vision are the light absorbing visual pigments (opsins) - embedded in the photoreceptors of the retina - that determine the spectral sensitivities of an organism and thus, shape its visual ability. The evolution of opsins is a textbook example of how changes at a molecular level - in the form of structural sequence alterations, and changes in gene expression - drive adaptation to divergent environments and lifestyles. Teleost fishes have become powerful models to study visual adaptations that can be linked to specific behaviours such as foraging and mating or to environmental factors such as the prevailing light habitat. Results of my previous work on the species-rich damselfish (Pomacentridae) demonstrated that an herbivorous feeding strategy is correlated with the expression of the long-wavelength sensitive (LWS) or 'red' opsin gene. Such a long-biased visual sensitivity increases the ability to detect an algae-green. By taking benefit of the Queensland Brain Institute's state of the art next generation sequencing, advanced neuroanatomical imaging, its access to marine field stations, and collaborating with world leaders in the field of vision research, I aim to further investigate the possible correlation of seeing red and being herbivorous in coral reef fishes. As vision is a complex process, a multidisciplinary approach is needed and my proposal moves literally from genes to behaviour by using a suite of up-to-date methods to specifically address the following questions: 1) Is the correlation of LWS expression to herbivory functional? Behavioural assays will be used to compare the spectral discrimination abilities between herbivorous versus non-herbivorous damselfish. 2) Is the retinal topography of herbivorous species specialized? In situ hybridization will visualize relative distribution of expressed opsins throughout the retina across damselfish differing in their feeding styles. 3) Is the link of LWS-expression to herbivory a common pattern also seen in different fish taxa? Next generation sequencing will be used to compare opsin expression in selected species-pairs of herbivorous versus non-herbivorous reef fish species. This work will elucidate how variability in reef fish visual phenotypes is linked to different lifestyles, and by this helps to unravel the forces that shape the complexity of coral reef ecosystems. Algae-feeding fish are key-players in coral reef ecology as they keep a vital balance between corals and algae and thus contribute to coral settlement or coral recovery. Ultimately, this study will help to better understand the crucial role herbivorous fish play in sustaining a healthy reef, especially in the light of recent declines of coral reefs worldwide.