Meeting Abstract

P1.11  Sunday, Jan. 4  Plastron redness in Red-bellied Turtles as an index for fitness TORREY, K.W.*; BAKER, P.J.; Swarthmore College; Swarthmore College ktorrey1@swarthmore.edu

Carotenoid-based ornamentation is thought to be an honest signal of health in many vertebrate taxa; however, this relationship has not been studied in turtles. The Eastern Red-bellied Turtle, Pseudemys rubriventris, displays carotenoid pigments as ornamentation on its plastron, (ventral shell); carotenoids may also be used, however, to protect the body from oxidative damage. One hypothesis is that because vertebrate animals cannot synthesize carotenoids de novo, their use for ornamentation demonstrates that oxidative defense needs are met and exceeded. To test our hypothesis that there is a relationship between plastron coloration and fitness, we matched principle components analysis of color values with data from assays measuring two indices of fitness, the carotenoid content and antioxidant capacity of plasma. We devised an inexpensive and effective way to quantify plastron coloration, by capturing digital images of turtle plastrons (n=8) under standardized conditions and lighting. From these images, measurements of hue, saturation, and brightness (HSB) were found by sampling randomized points on a grid overlay of the plastron. Analyzing the HSB values yielded a first principle component (PC1) that accounted for 79.3% of the variability in the HSB color space. PC1 correlated strongly with hue, (r²=0.687) saturation, (r²=0.866) and brightness (r²=0.786). Preliminary analysis has not indicated a relationship between PC1 scores and plasma carotenoid content, though further analysis will explore this connection. However, we found a strong correlation between PC1 scores and total antioxidant capacity of plasma (r²=0.583), supporting our hypothesis and suggesting that a relationship indicative of honest signaling may exist between plastron coloration and fitness in Red-bellied Turtles.