Temperature inevitably affects every level of biological organization (Guderley and St-Pierre, 2002). As such, physiological rate processes fluctuate with environmental temperature fluctuations unless core body temperature is maintained through thermoregulatory mechanisms or rates are buffered by compensatory responses, such as biochemical acclimatization (Seebacher, 2005; Bakken, 2008). Many reptiles, including alligators, modify biochemical characteristics in response to fluctuations in ambient temperature (Wilson and Franklin, 1999). Alligators may thermally compensate by increasing enzyme activity in the winter (Figure 1) to compensate for the effect decreased body temperatures has on physiological rates (Seebacher and Guderley et al., 2003). Alligators may do so by increasing the expression of genes responsible for the production of necessary enzymes (Seebacher and Guderley et al. 2003). Although decreased temperatures minimize the rate at which substrates interact with enzymes, an increase in the number of enzymes available will counteract the decreased rates to equilibrate such physiological functions near normal levels (Seebacher, 2005; Graves and Somero, 1982). Thus, many enzymes, especially those involved in ATP-producing pathways, are upregulated in the winter to maximize the rates of physiological functions (Seebacher, 2005; Crawford et al. 1999).
Furthermore, alligators may also thermally compensate by expressing many enzymes that exhibit lower thermal sensitivities in winter (Figure 2). Enzymes such as citrate synthase and cytochrome c oxidase are much less thermally sensitive in the winter, and can thus tolerate much more extreme temperatures than predicted (Seebacher and Guderley et al. 2003; Seebacher and Elsey et al., 2003). The decreased thermal sensitivity of these enzymes, as measured by their Q10 values, also explains the greater activity of some enzymes in colder climates. As such, the increased gene expression and the decreased thermal sensitivity of many enzymes are coadaptations that enable alligators to withstand temperatures far outside their thermal preference (Seebacher and Guderley et al. 2003). Recent discoveries of the alligator’s ability to biochemically acclimatize suggests that they are less thermally dependent on ambient temperature than previously thought (Seebacher and Guderley et al., 2003).
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