Comparison of neurobehavioral effects of methylmercury exposure in older and younger adult zebrafish (Danio rerio)

► We compared the neurobehavioral effects of methylmercury exposure in older and younger adult zebrafish. ► Methylmercury exposure produced learning impairments in a dose-dependent manner in both older and younger adult zebrafish. ► Methylmercury exposure produced learning impairments at a much lower concentration in older than younger adult zebrafish. ► Methylmercury exposure produced learning impairments more severely in older than younger adult zebrafish.