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What Do Lake Malawi Cichlid Fishes See?

The cichlid fishes of the Great Lakes of East Africa are a classic example of rapid adaptive radiation. Hundreds of species of these fishes have evolved from a common ancester in the past one million years. Their rapid speciation is thought to result in part from sexual selection, in which female mate preferences drive the evolution of male color patterns. As male color patterns change to better match the preferences of females, fish with these new color patterns become new species which no longer interbreed with fish having the old color patterns. In order to understand how this happens, we need to know how cichlids choose mates. This requires an understanding of t he visual sensitivities of these fish and whether visual sensitivities differ among species. <br/><br/>This project will examine several aspects of visual communication in the cichlid fishes of Lake Malawi, Africa. First, we will quantify the diversity of visual sensitivities in a broad range of cichlid species by sequencing the five cone opsin genes and measuring their relative expression levels in the retina. We already know that some Malawi cichlids are sensitive to ultraviolet wavelengths while others are not. This survey will determine whether ultraviolet sensitivity is widespread in this group and how it evolved. Second, we will measure the hues of cichlid color patterns as compared to their natural environment. This will determine whether color patterns also contain significant contributions in the ultraviolet part of the spectrum. Third, we will relate the visual system and color patterns in order to determine the conspicuousness of the color patterns as seen"through cichlid eyes." These studies will be related to ecological or behavioral factors to determine whether color usage is modified in different localities or under different social situations. We will also examine the importance of water quality and optical transmission for visual communication. Lake Malawi has historically been one of the clearest lakes in the world. Maintaining its clarity may be an important factor in preserving the spectacular diversity of these fishes.<br/><br/>The proposed effort will provide important scientific contributions to our understanding of how species diversity arises and is maintained. In addition, this work will integrate biological and physical approaches to understanding visual communication. It will also support the scientific training of a minority graduate student who will be fully funded by this project.

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