An Overview of Dioxin-Like Compounds, PCB, and Pesticide Exposures Associated with Sexual Differentiation of Neuroendocrine Systems, Fluctuating Asymmetry, and Behavioral Effects in Birds

Abstract

Dioxin, polychlorinated biphenyls (PCBs), and pesticides impact neural systems in birds due to interference with sexual differentiation. Early endocrine disrupting chemical (EDC) effects may delay maturation and have long-term effects on lifetime reproduction, especially in precocial birds that complete sexual differentiation prior to hatch. Semi-altricial and altricial species appear more resilient to EDC effects and show a gradient in sensitivity, especially in the neuroplastic song system. Embryonic steroid exposure occurs via maternally deposited steroids followed by embryo produced hormones; EDCs potentially affect these developing systems. As such, EDCs can impact lifelong fitness by acting on neural systems that regulate reproduction, metabolism, and behavior.

Key Words:

• Sexual differentiation
• endocrine disrupting chemicals
• precocial birds
• semi-altricial birds
• altricial birds
• lifetime fitness

ACKNOWLEDGEMENTS

This review reflects the scientific conclusions of the authors based on studies that have been supported in part by EPA grants # R826134010 (Star Grant) and R-82877801; Battelle contract for EPA-EDSTAC validation studies, NRI #92-37203 and NSF #9817024; MAES, University of Maryland, College Park; Fish and Wildlife Service. The authors also appreciate our wonderful collaborators and students, who have made these studies possible, including Ashley Barton, Kasen Whitehouse, Barnett Rattner, Mark Jaber, Joanne Beavers, Sara Pollack, Brandon Sitzmann, Kara Duffy, Anna Schlappal, Marci Strauss, Kimya Davani, and Krisztina Larson.

This mini review was developed from a platform presentation at the Society of Environmental Toxicology and Chemistry 2007 Symposium on “Common Effects Endpoints for Persistent Toxic Substances in Human and Ecological Epidemiology.”