John Wiley & Sons, Ltd.

Lifelong exposure to methylmercury disrupts stress‐induced corticosterone response in zebra finches (Taeniopygia guttata)

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Mercury can disrupt the endocrine systems of mammals and fish, but little is known about its effects on avian hormones. We employed an experimental manipulation to show that methylmercury suppresses the stress‐induced corticosterone response in birds, an effect previously unreported in the literature. Corticosterone regulates many normal metabolic processes, such as the maintenance of proper blood glucose levels during stressful daily fasting; an inability to increase corticosterone levels in response to stressors renders a bird less able to face a wide array of environmental challenges. We studied reproductively mature zebra finches that had been exposed to 0.0, 0.3, 0.6, 1.2, or 2.4 µg/g (wet weight, ww) dietary methylmercury throughout their life (i.e. from the egg onwards). In contrast to some field studies, we detected no significant change in baseline plasma corticosterone concentrations attributable to chronic methylmercury exposure. However, a comparison between the baseline corticosterone levels and levels after 30‐minutes of handling stress revealed that the ability of birds to mount a stress response was reduced with increasing blood total mercury concentration. These results are consistent with adrenal corticoid disruption due to chronic mercury exposure, and mirror a similar study on free‐living nestling songbirds exposed to environmental mercury. Environ Toxicol Chem © 2014 SETAC

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