Skin color variation among stingrays from the Georgia coast

REU Fellow: Lucía Ramírez-Joseph, University of North Carolina Greensboro

Mentor: Dr. Christine Bedore

Coloration is an important factor for stingrays to prevent predation. Stingrays are common prey for many large fish and marine mammal species, but differences in their color patterns have rarely been explored. For this study, four species of stingrays were studied: Atlantic Stingrays (Hypanus sabina), Bluntnose Stingrays (Hypanus say), Smooth Butterfly Rays (Gymnura micrura) and Spotted Eagle Rays (Aetobatus narinari). Even though all these species can be found in the Georgia coast, they have different patterns that may aid in camouflage. Therefore, the objectives of this study were to assess differences in the cell structure of each species, as well as quantify their body color. Melanophores are pigment-containing cells that can either disperse or aggregate pigment, which darkens or lightens the skin. To measure cell structure, we counted melanophores of different dispersal states using a melanophore index. To measure body color, we used photographic analysis in Photoshop by comparing skin values to a set of grey standards with known reflectance. All species had a similar number of cells, but differences in the frequency of each dispersal state. Their overall skin brightness also differed among species. This suggests that the different species evolved their coloration to camouflage themselves through different mechanisms but converged in developing similar color patterns and characteristics.