Dietary Selenomethionine Administration in the American Alligator (Alligator mississippiensis): Hepatic and Renal Se Accumulation and Its Effects on Growth and Body Condition.

Abstract

Selenium (Se) is an essential trace nutrient, but in excess, it can induce toxicity. Incomplete combustion of coal produces coal combustion wastes, which are enriched in Se and often disposed of in aquatic basins. While a multitude of studies have investigated Se accumulation in vertebrates, few studies have examined its effects on longer-lived top trophic carnivores, such as the American alligator (Alligator mississippiensis). In this study, alligators were fed one of three Dietary Treatments: mice injected with water (controls) or water supplemented with 1000 or 2000ppm selenomethionine (SeMet). Dietary Treatment significantly affected Se levels in both the liver (p<0.0001; raw mean±SE: 1000ppm group, 35.20±6.32ppm; 2000ppm group, 49.97±4.00ppm) and kidney (p<0.0001; raw mean±SE: 1000ppm group, 101.60±8.64ppm; 2000ppm, 96.38±5.81ppm), which were significantly higher in alligators fed SeMet than in controls. Post-treatment head length, used to control for size variation, was negatively related to both kidney (p=0.0142) and liver (p=0.0010) Se concentrations. Dietary treatment with SeMet significantly reduced body condition (1000ppm, p<0.0029; 2000ppm, p=0.0075), but it significantly increased growth (1000ppm, p<0.0001; 2000ppm, p=0.0316). Body condition and growth remained unchanged in control alligators (p>0.05). Our results demonstrate alligators are capable of accumulating high levels of Se through trophic transfer. The positive effects of accumulation on growth may demonstrate Se essentiality, whereas the negative effects on condition may demonstrate toxicity. Accumulation also was associated with mortality, further demonstrating toxicity. Future studies should further investigate the physiological effects of Se accumulation in long-lived, top-trophic carnivores.