Carotenoids are a diverse group of pigments that are readily produced by plants and algae but must be obtained by animals through dietary means. They are used by many taxonomic groups including lizards, birds, fish, mollusks, and insects for myriad functions including visual pigmentation, photoprotection, antioxidation, and signaling.
Most species of freshwater turtles exhibit the bright red, yellow, or orange colors characteristic of carotenoids on their ventral shells (plastrons) as hatchlings. This bright coloration is usually lost before sexual maturity because it dulls or fades into black or brown; notable exceptions include the western painted turtle (Chrysemys picta bellii; pictured). Very little is known about the mechanism and function of plastron coloration in hatchlings or adults, despite the likely costliness of color production and the known adaptive advantages of bright colorations found in many other species. A focus of my dissertation work is identifying the function of pigments in freshwater turtles, especially Chrysemys picta, and elucidating their adaptive significance.
Identifying the integumentary pigments of freshwater turtles and their functions is important to establish the feasibility of pigments as important antioxidants and will also answer important evolutionary ecology questions about the adaptive significance of coloration in these organisms. Freshwater turtles are currently one of the fastest declining groups of vertebrates and understanding their natural history and functional morphology may contribute to their conservation.
The Graduate Alumni Research Award allowed me to travel to Kevin McGraw’s lab at Arizona State University to conduct specialized analyses that determined the specific pigments present in painted turtle shell. I verified that the shell contains high levels of carotenoids and melanins and these data lay the foundation for the experiments that will make up my dissertation. I am grateful to the Graduate Studies Office and alumni for providing funding for this portion of the project.