Antioxidant Enzymes in Destructible and Non-Destructible Tissues in American Alligators (Alligator mississippiensis)

Abstract

Abstract. Anthropogenic-derived stressors represent an ever-increasing risk to organisms worldwide. To understand the effects of stressors on organisms, many studies measure an organism's oxidative status. American alligators (Alligator mississippiensis) are long-lived, top trophic carnivores that have been suggested to serve as an indicator of environmental quality. Raised tail scutes on crocodilians are often marked to enable easy subsequent identifications. Recent studies have illustrated scutes can also serve as indicators of stress or toxicant exposure. In this study, we investigated another role of scutes: as potential non-destructive (i.e., not requiring euthanasia to obtain) indicators of oxidative status. Three antioxidant enzymes, superoxide-dismutase (SOD)-1, SOD2, and glutathione peroxidase (GPX), were measured in non-destructible (i.e., tail scutes) and destructible tissues using Western blot. Enzyme levels were then compared with body condition and health using principal component analysis (PCA). Linear mixed models revealed that tissue had a significant effect on relative enzyme level (all P < 0.05). PCAs revealed significant groupings (eigenvalues > 1) of both tail scutes and destructible tissues. Levels of GPX1 in tail scutes were positively related with body condition and organ mass. Our results suggest antioxidant enzyme levels in alligator tail scutes may serve as important, non-destructive indicators of internal organ and whole-body oxidative status. In addition, tail scute antioxidants may also provide insight into alligator body condition and health. Future studies involving captive or wild individuals should incorporate measuring tail scute antioxidant enzyme levels, along with more traditional stress parameters, to better understand how stressors affect crocodilians.