Meeting Abstract
Variation in visual systems may lead to differences in visually mediated behaviors. In fishes, visual sensitivity is correlated with behaviors such as female mate preferences. In darters (genus Etheostoma), males express elaborate breeding coloration and female preferences are based on male coloration. Darters are dichromatic with photoreceptors sensitive to medium and long wavelengths of light. The wavelength of peak sensitivity in both photoreceptor types varies both among and within species. Visual sensitivity is determined predominantly by visual pigments composed of an opsin protein bound to a light-sensitive chromophore. Proximately, at least two molecular mechanisms underlie variation in visual sensitivity: 1) Structural changes, wherein sequence differences in the coding regions of opsin proteins alter the types and spectral characteristics of the visual pigment and 2) differential gene expression, which alters spectral sensitivity through regulation of opsin genes. We tested whether variation in darter visual sensitivity is due to differences in gene sequence, gene expression, or both. Sequencing the opsins in 25 species of darters, we found variation in spectral tuning sites among species. Structural changes in the medium wavelength sensitive opsin appear to contribute most to the measured variation in visual sensitivity. Additionally, qPCR methods assessing relative levels of gene expression of opsins suggest that regulatory changes also contribute to the diversity of visual systems in darters. By linking visual physiology and genetic mechanisms within and among species, our results help elucidate the relative contributions of structural and regulatory changes during the diversification of visual systems.
