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

珊瑚礁，特别是世界著名的大堡礁，是地球上最多样和最丰富多彩的栖息地之一，许多海洋生物利用颜色视觉寻找食物，识别配偶和敌人，或竞争资源。视觉的核心是吸收光的视觉色素(视蛋白)--嵌入在视网膜的光感受器中--它决定了有机体的光谱敏感性，从而塑造了它的视觉能力。视蛋白的进化是一个教科书上的例子，说明了分子水平上的变化--以结构序列改变和基因表达变化的形式--如何驱动对不同环境和生活方式的适应。硬骨鱼已经成为研究视觉适应的有力模型，视觉适应可以与特定行为有关，如觅食和交配，或与环境因素有关，如占主导地位的光照栖息地。我之前对物种丰富的豆娘鱼(Pomacentridae)的研究结果表明，草食性摄食策略与长波敏感(LWS)或‘红色’视蛋白基因的表达有关。这种长期偏向的视觉敏感度提高了检测藻绿色的能力。通过昆士兰大脑研究所最先进的下一代测序、先进的神经解剖成像、其对海洋野外观测站的访问，以及与视觉研究领域的世界领先企业的合作，我的目标是进一步研究珊瑚礁鱼类中看到红色与食草性之间的可能联系。由于视觉是一个复杂的过程，需要一种多学科的方法，我的建议通过使用一套最新的方法从基因转移到行为，具体解决以下问题：1)LWS表达与食草动物的相关性是否具有功能？行为分析将用于比较食草性和非食草性丹自鱼之间的光谱辨别能力。2)草食性物种的视网膜地形图是专门的吗？原位杂交将显示表达的视蛋白在不同摄食方式的雏鱼视网膜中的相对分布。3)LWS表达与食草性的联系是不是在不同的鱼类类群中也可以看到的共同模式？下一代测序将用于比较选定物种-食草性和非食草性珊瑚鱼物种对视蛋白的表达。这项工作将阐明珊瑚礁鱼类视觉表型的可变性如何与不同的生活方式有关，并由此有助于解开塑造珊瑚礁生态系统复杂性的力量。以藻类为食的鱼类是珊瑚礁生态中的关键角色，因为它们在珊瑚和藻类之间保持着至关重要的平衡，从而有助于珊瑚定居或珊瑚恢复。最终，这项研究将有助于更好地理解食草鱼在维持一个健康的珊瑚礁方面所发挥的关键作用，特别是鉴于最近世界各地珊瑚礁的减少。

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.