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

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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.