Morran Spencer A M, Elliott John E, Young Jessica M L, Eng Margaret L, Basu Niladri, Williams Tony D
Department of Biological Sciences, Simon Fraser University, Burnaby, BC, Canada.
Environment and Climate Change Canada, Science & Technology Branch, Pacific Wildlife Research Centre, Delta, BC, Canada.
Ecotoxicology. 2018 Apr;27(3):259-266. doi: 10.1007/s10646-017-1890-4. Epub 2018 Jan 8.
Methylmercury causes behavioural and reproductive effects in adult mammals via early developmental exposure. Similar studies in birds are limited and mostly focussed on aquatic systems, but recent work has reported high blood mercury concentrations in terrestrial, passerine songbirds. We used the zebra finch (Taeniopygia guttata) as a model to explore the long-term effects of early developmental exposure to methylmercury exposure. Chicks were dosed orally with either the vehicle control, 0.0315 µg Hg/g bw/day, or 0.075 µg Hg/g bw/day throughout the nestling period (days 1-21 post-hatching). We then measured (a) short-term effects on growth, development, and behaviour (time to self-feeding, neophobia) until 30 days of age (independence), and (b) long-term effects on courtship behaviour and song (males) and reproduction (females) once methylmercury-exposed birds reached sexual maturity (90 days post-hatching). High methylmercury treated birds had mean blood mercury of 0.734 ± 0.163 µg/g at 30 days post-hatching, within the range of values reported for field-sampled songbirds at mercury contaminated sites. However, there were no short-term effects of treatment on growth, development, and behaviour of chicks, and no long-term effects on courtship behaviour and song in males or reproductive performance in females. These results suggest that the nestling period is not a critical window for sensitivity to mercury exposure in zebra finches. Growing nestlings can reduce blood mercury levels through somatic growth and depuration into newly growing feathers, and as a result they might actually be less susceptible compared to adult birds receiving the same level of exposure.
甲基汞通过早期发育暴露对成年哺乳动物的行为和繁殖产生影响。鸟类方面的类似研究有限，且大多集中在水生系统，但最近的研究报告称，在陆地雀形目鸣禽中血液汞浓度很高。我们以斑胸草雀（Taeniopygia guttata）为模型，探讨早期发育暴露于甲基汞的长期影响。在整个育雏期（孵化后第1 - 21天），给雏鸟口服给予溶剂对照、0.0315μg Hg/g体重/天或0.075μg Hg/g体重/天。然后，我们测量了：（a）对生长、发育和行为（自主进食时间、新物恐惧症）的短期影响，直至30日龄（独立）；（b）一旦甲基汞暴露的鸟类达到性成熟（孵化后90天），对求偶行为和鸣叫（雄性）以及繁殖（雌性）的长期影响。高甲基汞处理的鸟类在孵化后30天的平均血液汞含量为0.734±0.163μg/g，处于汞污染地点野外采样鸣禽报告的数值范围内。然而，处理对雏鸡的生长、发育和行为没有短期影响，对雄性的求偶行为和鸣叫或雌性的繁殖性能也没有长期影响。这些结果表明，育雏期不是斑胸草雀对汞暴露敏感的关键窗口期。正在成长的雏鸟可以通过身体生长和将汞净化到新生长的羽毛中来降低血液汞水平，因此与接受相同暴露水平的成年鸟类相比，它们实际上可能更不易受影响。
