Bottini Claire L J, Henry Calista J, MacDougall-Shackleton Scott A
Department of Biology, The University of Western Ontario, London, Ontario, Canada.
Advanced Facility for Avian Research, University of Western Ontario, London, Ontario, Canada.
J Neuroendocrinol. 2025 Jun;37(6):e70027. doi: 10.1111/jne.70027. Epub 2025 Apr 21.
Exposure to methylmercury (MeHg) on breeding grounds may have numerous deleterious effects on birds, including neurotoxicity, disruption of hormones, and impaired reproduction. But it is unknown if MeHg exposure on wintering grounds can carry over and produce negative effects on the following spring breeding seasonal transition. To evaluate this, we exposed male captive song sparrows (Melospiza melodia) to environmentally relevant levels of dietary MeHg for 3 months during winter. We then photostimulated the birds with a long-day photoperiod and observed them for 21 days post-exposure. Contrary to our predictions, we found no carry-over effects of MeHg on the timing of changes in spring reproductive physiology assessed by testes mass, syrinx mass, plasma androgen concentrations, number of GnRH neurosecretory cells, and body condition. However, following photostimulation, MeHg-exposed birds had smaller cloacal protuberances. Although we observed no obvious effects on the timing of reproductive onset, the results suggest that winter MeHg exposure could induce carry-over effects on secondary sexual traits that may affect birds' breeding performance. Overall, our findings indicate that songbirds can buffer against the main effects of prior winter MeHg exposure so as to not delay reproductive onset in spring, but more studies are required for long-term effects on breeding performance.
在繁殖地接触甲基汞（MeHg）可能会对鸟类产生许多有害影响，包括神经毒性、激素紊乱和繁殖能力受损。但尚不清楚在越冬地接触甲基汞是否会产生延续效应，并对随后春季的繁殖季节转换产生负面影响。为了评估这一点，我们在冬季对圈养的雄性歌带鹀（Melospiza melodia）进行了为期3个月的环境相关水平的膳食甲基汞暴露实验。然后，我们用长日照光周期对这些鸟类进行光刺激，并在暴露后观察它们21天。与我们的预测相反，我们发现甲基汞对通过睾丸质量、鸣管质量、血浆雄激素浓度、促性腺激素释放激素（GnRH）神经分泌细胞数量和身体状况评估的春季生殖生理变化时间没有延续效应。然而，在光刺激后，接触甲基汞的鸟类泄殖腔突起较小。虽然我们没有观察到对生殖开始时间的明显影响，但结果表明，冬季接触甲基汞可能会对第二性征产生延续效应，这可能会影响鸟类的繁殖性能。总体而言，我们的研究结果表明，鸣禽可以缓冲先前冬季甲基汞暴露的主要影响，从而不会延迟春季的生殖开始，但需要更多研究来了解其对繁殖性能的长期影响。
