The effect of dietary carotenoid increase on painted turtle spot and stripe color

Determination of how carotenoid-based color patches change with pigmentary access is important to understanding color patch function in animals. We performed a carotenoid addition experiment on male painted turtles (Chrysemys picta) to determine if an increase in dietary carotenoids led to location-specific changes in painted turtle spot and stripe color. Turtles fed large quantities of carotenoids had increased yellow chroma in chin stripes and increased red chroma in the neck and carapace stripes, as well as reduced ultraviolet (UV) chroma in the neck (orange to the human eye) and fore -limb (red to the human eye) stripes. Turtles fed large quantities of carotenoid had reduced brightness (B₁) in the hind-limb stripes (red to the human eye) as well as reduced red and UV chroma in the post orbital spot of turtles (yellow to the human eye) compared to turtles fed moderate amounts of carotenoid. These results imply that integumentary spot and stripe colors are dependent upon carotenoid access, and increased lutein access leads to increased yellow and red chroma, as well as reduced ultra-violet chroma and brightness in male painted turtles. These results are discussed with respect to dietary access to carotenoids and color in other model systems, and the possibility that spot and stripe color functions as a visual signal.