Reproductive and developmental effects of PHAHs in amphibians

In the last years a world-wide trend of decreasing amphibian populations in different types of habitats has been observed. Pollution with persistent substances such as polyhalogenated aromatic hydrocarbons (PHAHs) might be one part of the puzzle. PHAHs are known to affect a wide variety of physiological processes including levels of circulating thyroid hormones and levels and pattern of active forms of vitamin A. Thyroid hormones are controlling the onset of metamorphosis in amphibians whereas vitamin A is responsible for early tissue development. In this study particular emphasis will be put on effects of PHAHs and their hydroxylated metabolites on development, reproduction, metamorphosis and migration of amphibians resulting from disturbances of physiological functions such as thyroid hormones or retinoid pattern dependent processes and the consecutive effects in amphibians of all stages (e.g. eggs, larvae and adults). This study will focus on the subtle effects of low levels of PHAHs and their effects in amphibians which have been shown already in a one year pilot project.