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Methylmercury effects on avian brains.
Claire L J Bottini1, Scott A MacDougall-Shackleton2
1University of Western Ontario, Department of Biology, 1151 Richmond St., London, Ontario N6A 5B7, Canada; Advanced Facility for Avian Research, University of Western Ontario, London, Ontario, Canada.
Neurotoxicology
|April 14, 2023
Summary
Methylmercury (MeHg) is a neurotoxic contaminant. Research on its effects on the avian brain is limited, with oxidative stress markers most consistently impacted, highlighting a need for more comprehensive studies.
Area of Science:
- Environmental toxicology
- Avian neurobiology
- Neuroscience
Background:
- Methylmercury (MeHg) is a widespread neurotoxicant with known harmful effects on organisms.
- Birds are valuable models for studying vocal learning and adult neuroplasticity, yet MeHg's neurotoxic effects in avian brains are less understood than in mammals.
- Literature on MeHg's impact on the avian brain shows a low publication rate despite increasing interest in environmental contaminants.
Purpose of the Study:
- To survey and analyze the existing literature on methylmercury's biochemical effects on the avian brain.
- To identify trends in research, common neurotoxicological measures, and sensitive biomarkers of MeHg exposure in birds.
- To compare MeHg neurotoxicity mechanisms in birds with those in mammals and identify research gaps.
Main Methods:
- Systematic literature review of studies investigating methylmercury and avian brain neurochemistry.
- Analysis of publication trends, temporal changes in measured neural effects, and consistently affected biomarkers.
- Comparison of mammalian and avian neurotoxicological data and identification of research gaps in avian species and life stages.
Main Results:
- Publication rates on MeHg and avian brains are low but increasing, correlating with environmental awareness and regulations.
- Markers of oxidative stress were most consistently affected by MeHg exposure in birds.
- Other potentially sensitive neural targets include NMDA receptors, acetylcholinesterase, and Purkinje cells, though more validation is needed for neurotransmitter systems.
Conclusions:
- The current literature on MeHg's effects on the avian brain is insufficient to fully construct an adverse outcome pathway.
- Significant research gaps exist for specific avian taxa (e.g., songbirds) and life stages (e.g., fledgling, non-reproductive adults).
- Future studies should integrate molecular, physiological, and behavioral outcomes to assess ecologically relevant impacts of MeHg on birds, particularly under environmental stress.
