DISSERATION RESEARCH: Spectral Tuning to Heterogeneous Backgrounds: Distribution of Double Cone Opsins within the Retinas of Lake Malawi Cichlids

物种通过自然选择的过程来适应环境。在水生动物中，视觉系统通常对环境中最丰富的光的波长很敏感。光被视网膜中的视觉色素吸收，启动了视觉过程。然而，水中的背景光谱会随着视角的变化而变化，这些不同的光谱投射到视网膜的不同区域。因此，用于检测对象的最佳视觉色素被预测为根据视网膜区域的不同而不同。在这项研究中，视觉色素的空间分布将被绘制在马拉维湖几种不同光照栖息地、觅食模式和属的慈鱼的视网膜上。视网膜将从野生捕获的和实验室饲养的慈鱼身上获得。一些慈鱼将在逆光条件下饲养，不同物种的结果将进行比较，以确定光栖息地、觅食模式和遗传对视觉色素分布的影响。这项研究是首次定量研究视觉色素在视网膜中的分布与观看背景的关系。如果色素在鱼类中的视网膜分布不同，这些差异可能也会导致视觉信号的差异。视觉敏感度和颜色信号的共同进化可能有助于解释马拉维湖近1000种叶蝉类物种是如何在过去100-200万年内进化的。此外，这个戏剧性的进化例子将被用来在城市高中教授适应和物种形成。

Species adapt to their environment through the process of natural selection. In aquatic animals, visual systems generally are sensitive to the wavelengths of light that are most abundant in their environment. Light is absorbed by visual pigments in the retina, initiating the process of vision. However, the background light spectrum in water changes with angle of view, and these distinct spectra project onto different regions of the retina. As a result, the optimal visual pigments for detecting objects are predicted to differ by retinal region. In this study, the spatial distributions of visual pigments will be mapped in retinas of several cichlids from Lake Malawi that differ in light habitat, foraging mode, and genus. Retinas will be obtained from both wild-caught and lab-reared cichlids. Some cichlids will be reared under inverted light conditions, and results from different species will be compared to determine the effects of photic habitat, foraging mode, and genetics upon visual pigment distributions.This study is among the first to quantitatively examine the retinal distribution of visual pigments in relation to viewing backgrounds. If retinal distributions of pigments have diversified among fishes, these differences might drive visual signals to diverge also. Coevolution of visual sensitivity and color signals could help explain how nearly 1000 cichlid species evolved in Lake Malawi just in the last 1-2 million years. In addition, this dramatic example of evolution will be used to teach adaptation and speciation at urban high schools.