Stable Carbon and Nitrogen Isotope Discrimination and Turnover in Pond Sliders Trachemys Scripta: Insights for Trophic Study of Freshwater Turtles

Abstract

Abstract The ecologies of vertebrate species have been increasingly studied via stable isotope analyses of small quantities of body tissues. However, critical assumptions relating to the consistency in stable isotopic values in consumer tissues and their diet as well as the rate of incorporation of diet-derived stable isotopes into consumer tissues remain poorly validated for most taxa despite numerous stable isotope studies targeting natural systems. In this study, we measured stable carbon and nitrogen diet–tissue discrimination and elemental turnover in whole blood, red blood cells, blood plasma, brain, liver, pectoralis major muscle, pubioshiofemoralis internus muscle, stratum corneum (sc) dermis, and stratum germinativum (sg) dermis of Pond Sliders (Trachemys scripta) fed ad libitum on two isotopically distinct diets. Turtles were fed a soy-based control diet (32% protein, 3% lipids, 4% fiber), and after 146 d, a subset was switched to a fish meal-based experimental diet (44% protein, 24% lipids, 3% ...