Leary Christopher J, Lippincott Johnny, Harris Samuel, Hawkins Doyle L
University of Mississippi, Department of Biology, Box 1848, Oxford, MS 38677, USA.
University of Mississippi, Department of Biology, Box 1848, Oxford, MS 38677, USA.
Gen Comp Endocrinol. 2015 Mar 1;213:32-9. doi: 10.1016/j.ygcen.2014.12.017. Epub 2015 Jan 6.
Male courtship displays may be regulated by, and affect the production of, circulating hormones. The Energetics-Hormone Vocalization (EHV) model, for example, posits that interactions among chorusing male anuran amphibians stimulate androgen production that then mediates an increase in vocal effort. Increased vocal effort is expected to deplete energy reserves and increase glucocorticoid levels that, in turn, negatively affect androgen levels and vocalization. Androgen levels, glucocorticoid levels, and vocal effort are thus expected to increase across and within nights of chorus activity and should be positively correlated in calling males; energy reserves should decline temporally and be inversely related to glucocorticoid levels. We tested predictions of the EHV model in the green treefrog, Hyla cinerea. Consistent with the model, both testosterone and dihydrotestosterone levels increased across the breeding season in calling males. However, testosterone levels decreased and dihydrotestosterone levels did not change within nights of chorus activity, suggesting that chorusing behavior did not drive the seasonal elevation in androgens. Corticosterone (CORT) level remained relatively stable across the breeding season and decreased within nights of chorus activity, contrary to model predictions. Body condition, the proxy for energetic state, was inversely correlated with CORT level but discrepancies between model predictions and temporal patterns of CORT production arose because there was no evidence of a temporal decrease in body condition or increase in vocal effort. Moreover, androgen and CORT levels were not positively correlated with vocal effort. Additional ecological and physiological measures may be needed to support predictions of the EHV model.
雄性求偶行为可能受循环激素的调节，并影响其分泌。例如，能量 - 激素发声（EHV）模型假定，合唱中的雄性无尾两栖动物之间的相互作用会刺激雄激素的分泌，进而介导发声努力的增加。预计发声努力的增加会耗尽能量储备并提高糖皮质激素水平，而这反过来又会对雄激素水平和发声产生负面影响。因此，预计雄激素水平、糖皮质激素水平和发声努力在合唱活动的各个夜晚以及同一夜晚内都会增加，并且在鸣叫的雄性中应该呈正相关；能量储备应该随时间下降，并且与糖皮质激素水平呈负相关。我们在灰树蛙（Hyla cinerea）中测试了EHV模型的预测。与该模型一致，在繁殖季节，鸣叫雄性的睾酮和双氢睾酮水平均有所增加。然而，在合唱活动的夜晚内，睾酮水平下降，双氢睾酮水平没有变化，这表明合唱行为并未推动雄激素的季节性升高。与模型预测相反，皮质酮（CORT）水平在整个繁殖季节保持相对稳定，并在合唱活动的夜晚内下降。身体状况作为能量状态的指标，与CORT水平呈负相关，但由于没有证据表明身体状况随时间下降或发声努力增加，因此出现了模型预测与CORT分泌时间模式之间的差异。此外，雄激素和CORT水平与发声努力没有正相关。可能需要额外的生态和生理测量来支持EHV模型的预测。
