Meeting Abstract
Many reef fishes exhibit dynamic coloration and body patterns that can change under nervous or hormonal 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) and the smooth butterfly ray (Gymnura micrura) are benthically-oriented elasmobranchs with elaborate spot patterns that provide effective camouflage within their habitats. This patterning, when coupled with the ability to alter melanin concentrations in response to background color, could increase background matching effectiveness in these species. Both species have been anecdotally noted to lighten or darken skin color. However, despite the wide array of studies conducted on color change for enhanced background-matching capabilities in bony fish, this ability remains understudied among elasmobranchs. To investigate this, we housed rays in either black or white tanks for one week and photographed the rays daily. Stingrays in black tanks significantly darkened skin color over the seven-day period whereas rays in white tanks significantly lightened their skin color during the same period. On the last day, blood and tissue samples were taken in order to further examine the underlying physiological mechanisms that control color change through quantification of key hormones and melanin concentrations.
