Carotenoid composition of colorful body stripes and patches in the painted turtle (Chrysemys picta) and red-eared slider (Trachemys scripta)

The objective quantification of integumentary color and its pigmentary basis have been relatively little studied in turtles. We used reflectance spectrometry to measure the color of the chin, neck, and leg stripes and spots of the painted turtle (Chrysemys picta) and the red-eared slider (Trachemys scripta), and we used absorbance spectrometry and high-performance liquid chromatography to identify pigments in these colored patches. Both species had stripes and patches that were predominantly yellow and orange, but the yellow stripes typically contained a small ultraviolet (UV) reflectance peak. Chin, neck, and leg stripes of the painted turtle and chin and neck stripes of the red-eared slider contained an unidentified apocarotenoid and a ketocarotenoid (astaxanthin), but the postorbital eyespot of the red-eared slider contained only astaxanthin. These findings add painted turtles and red-eared sliders to the growing list of animals that use carotenoids in part to generate red, orange, yellow, and UV colors. We discuss these findings in the context of dual pigment production, pigment metabolic production costs, immune system health, and visual signal use in emydid turtles and other vertebrates.