Corticosteroids are steroid hormones produced by the vertebrate adrenal (interrenal) gland in response to physiological and environmental stimuli, including stress. When faced with a stressor, an organism must take the energy necessary for growth and reproduction and use that energy to survive the stressful event. Amphibians, especially frogs, are an excellent group to examine the role of corticosteroids as they have different effects depending on developmental stage. During premetamorphic stages, corticosteroid levels are low due to the need to use energy for growth. However, if tadpoles encounter a stressor such as a predator, tadpoles decrease locomotor activity and foraging over the short term (Maher et al, 2013). The objective of this study is to determine how reducing corticosterone (a corticosteroid) levels at premetamorphic larval stages impact tadpole development. In order to experimentally reduce CORT levels below previous studies, the adrenal inhibitor mitotane, alone, and in combination with CORT synthesis inhibitor metyrapone were used. Tadpoles of the Hyla versicolor/chrysoscelis complex (Gosner stages 26-31; Gosner 1960) were exposed to different treatments: vehicle, exogenous metyrapone, exogenous mitotane, and a mixture of metyrapone and mitotane. Predators were added to half of the treatment tanks after 8 days. After 28 days, morphological measurements, (Gosner stage, snout-vent length, tail length, tail height, tail muscle length, and tail muscle height) were taken for each tadpole. An ELISA was used to examine differences in corticosterone levels among tadpoles. CORT was decreased by 20% using metyrapone and 50% using mitotane. When predators were added, most of the treatment groups had an increase in tail muscle and Gosner stage. This research is important to understand the impact that man-made chemicals have on tadpole metamorphosis.
|Commitee:||Essner, Richard, Williams, Jason|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 55/05M(E), Masters Abstracts International|
|Subjects:||Neurosciences, Endocrinology, Zoology, Developmental biology|
|Keywords:||Corticosterone, Metamorphosis, Mitotane, Tadpoles|
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