Evolution of the Visual System in Cichlids and its Impact on Speciation

Cichlids are a colorful group of over 2000 species of fresh water fishes. They have adaptively radiated in a variety of habitats and are behaviorally complex. As a result, cichlids have highly diverse visual sensitivities. Visual sensitivities are set by opsin genes which combine with retinal to produce visual pigments sensitive to different wavelengths of light. Riverine cichlids vary their visual sensitivities through development, with larvae expressing shorter wavelength sensitive opsins, juveniles expressing medium wavelength opsins, and adults expressing longer wavelength opsins. Cichlids from the African Great Lakes vary adult opsin expression by altering the developmental program to express different opsin subsets. This produces sister species which differ in spectral sensitivities. These differences are some of the largest known differences in vertebrates, and are related to cichlid ecology and speciation. We have exploited the genomic power of the cichlid system to identify genes and mutations that cause differential opsin expression. We find that rapid changes in the regulation of transcription factors have facilitated large sensitivity shifts. We are working to understand how cichlid species see the world. Behavioral experiments suggest that cichlid do indeed use color vision to survive and thrive. Cichlids are therefore a unique model for exploring how visual systems evolve in a changing world.