Meeting Abstract
Many reef fishes exhibit dynamic coloration and body patterns that can change under nervous control. Lowe et al (1996) showed that hammerheads in high UV environments have higher skin melanin concentrations, which likely functions as a protective mechanism against UV damage. However, several species of benthic sharks and rays likely alter melanin concentrations in the skin to provide background matching for camouflage. The yellow stingray (Urobatis jamaicensis) is a small, reef-dwelling elasmobranch with elaborate spot patterns that provides effective camouflage against their rock-reef background. Because yellow stingrays likely use this camouflage as a predator avoidance strategy, melanin responses to UV light may be supplemented by responses to other environmental mechanisms such as habitat color/brightness. To investigate this hypothesis, we housed rays in either black or white tanks for one week. Stingrays in black tanks darkened their skin approximately 96%, whereas rays in white tanks lightened their skin color an average of 142%. When moved to the opposite color, all rays either darkened or lightened according to their new tank. To investigate the role of UV light on changes in camouflage, rays were housed individually in black and white tanks and were held in either 24h light (UV present) or 24h dark (UV absent). Preliminary results indicate that rays adjust to their tank conditions independent of the presence of UV; rays in both 24h light and 24h dark treatments darkened or lightened according to their tank color within the 3-day test period. We plan to further examine the underlying physiological mechanisms that control color change in the yellow stingray, including the extent to which color change is visually mediated.
