Effects Of The Developmental Environment On Oxidative Damage And Antioxidants In Red-Eared Slider Turtle (trachemys Scripta Elegans) Hatchlings

摘要

Developmental environments influence many individual phenotypes. However, currently we have a limited understanding of how the developmental environment influences oxidative stress resistance phenotypes. Oxidative stress is defined as a physiological state during which the production of harmful free radicals exceeds the protective capabilities of antioxidants. Variations among adults in susceptibility to oxidative stress can have important consequences for life history strategies and fitness related traits. Our work was aimed at providing insight in to the role that the developmental environment plays on oxidative stress phenotypes in the model oviparous reptile the red-eared slider turtle (Trachemys scripta elegans). Here, we conducted three independent experiments to determine if hatchling levels of oxidative damage and antioxidant activities vary following manipulations of the incubation thermal environment. First, to investigate if temperature fluctuations elicit oxidative stress during incubation, eggs from clutches were randomly assigned to a constant temperature (29.5°C) or daily sinusoidal fluctuating temperature incubation (28.7+3°C) treatment. Second, to assess the effect of temperature fluctuation frequency on oxidative stress, eggs were incubated in one of three fluctuating incubation regimes; 28.7+3°C sinusoidal fluctuations every 12 (Hyper), 24 (Normal), or 48 hours (Hypo). Third, we tested the influence of average incubation temperature on hatchling oxidative damage and total antioxidant capacity (TAC). To test this, eggs were incubated in daily sinusoidally fluctuating incubation temperature regime with a mean temperature of 26.5 ° C (Low), 27.1 °C (Medium), or 27.7 °C (High). We report that regardless of any thermal manipulation, no treatment effects on hatchling accumulation of oxidative damage were observed. This finding suggests that T. scripta hatchlings have sufficient antioxidant defenses that effectively protect individuals from temperature induced oxidative stress during incubation. However, hatchling TAC was influenced by both temperature fluctuation frequency and average incubation temperature. Following incubation with a low frequency of temperature fluctuations individuals had a reduced TAC, while incubation at a lower average temperature was associated with enhanced TAC. These results indicate that hatchling TAC is likely sensitive to the developmental thermal environment and may have important future consequences for hatchling fitness. In addition to temperature, we also saw that both oxidative damage and TAC were significantly related to clutch identity suggesting that there are either strong maternal or genetic factors influencing early life oxidative status of T. scripta.