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CONTAMINANT-ASSOCIATED ENDOCRINE DISRUPTION IN REPTILES.
Guillette Jr., L. CONTAMINANT-ASSOCIATED ENDOCRINE DISRUPTION IN REPTILES. Chapter 10, Donald W. Sparling, Greg Linder, Christine A. Bishop (ed.), Ecotoxicology of Amphibians and Reptiles. SETAC Press, Pensacola, FL, , 595-615, (2000).
The data presented suggest that contaminants can alter the endocrine and reproductive system of reptiles by mimicking hormones and by various mechanisms other than direct hormonal mimicry. However, these data indicate, as do many other studies using various vertebrates, that a focus on estrogenic chemicals is unwarranted, as endocrine-disrupting chemicals appear to involve a number of different hormonal signals (e.g., androgens, progestins, thyroid hormones) (Gray et al. 1996; Crain and Guillette 1997). The data obtained for reptiles support other studies reporting various abnormalities in wildlife (Crain and Guillette 1997) and suggest that additional species must be investigated. Species variation does occur and has been noted in the few studies performed on reptiles to date. Thus, direct linkages of specific endpoints (e.g., sex reversal) between species are not necessarily likely or expected. However, an understanding of the variation existing within and between natural populations and among species from differing phylogenetic histories is essential if we are to determine the risk EDCs pose to wildlife populations, including amphibians and reptiles. It is important that appropriate endpoints are examined for each species, and that endpoints representative of responses to ecologically relevant mixtures be used. Finally, embryonic, fetal and neonatal exposures should be focal aspects of any future study on endocrine disruption. Although it is important to establish activational endpoints in adults of various reptilian species, the influence on developing embryos appears to be lifelong and would have the greatest impact on population growth and survival.