Embryonic exposure to environmentally relevant concentrations of a brominated flame retardant reduces the size of song‐control nuclei in a songbird

Environmental contaminants have the potential to act as developmental stressors and impair development of song and the brain of songbirds, but they have been largely unstudied in this context. 2,2′,4,4′,5‐Pentabromodiphenyl ether (BDE‐99) is a brominated flame retardant congener that has demonstrated endocrine disrupting effects, and has pervaded the global environment. We assessed the effects of in ovo exposure to environmentally relevant levels of BDE‐99 on the neuroanatomy of the song‐control system in a model songbird species, the zebra finch (Taeniopygia guttata). Embryos were exposed via egg injection to a vehicle control (DMSO), 10, 100, or 1000 ng BDE‐99/g egg on the day the egg was laid. Chicks were raised to sexual maturity to investigate long‐term effects of BDE‐99 on the adult male brain. Three key song‐control nuclei (Area X, HVC, RA) all showed a dose‐dependent trend toward decreasing volume as BDE‐99 concentration increased, and birds exposed to 1000 ng/g in ovo BDE‐99 had significantly smaller song‐control nuclei volume compared to control birds. High environmental concentrations of BDE‐99 in avian tissues can be within that range and thus could affect development of the song‐control system in birds, and potentially other processes. We previously found that BDE‐99 exposure during the nestling period had no effect of on the song‐control system, although it did have significant effects on some behaviural endpoints. Taken together, these results suggest that exposure to polybrominated diphenyl ether (PBDEs) during critical developmental windows can significantly alter neurological development. © 2018 Wiley Periodicals, Inc. Develop Neurobiol, 2018