Our Stolen Futurea book by Theo Colborn, Dianne Dumanoski, and John Peterson Myers


  Willingham, E, T Rehn, JT Sakata and D Crews. 2000. Embryonic Treatment with Xenobiotics Disrupts Steroid Hormone Profiles in Hatchling Red-Eared Slider Turtles (Trachemys scripta elegans). Environmental Health Perspectives 108(4): 329-332.



This paper examines the impact of three xenobiotic compounds on sexual differentiation and hormonal status of turtles. They find that each of the compounds studied, the PCB mixture Arochlor 1242, trans-nonachlor and chlordane have significant effects. Certain effects are evident during fetal development, particularly alterations in the expected sex ratio of exposed eggs. [Sex determination in this species is normally by clutch incubation temperature. More...] Other effects continue into turtle adulthood even the exposure took place only in the egg.

In the experiment, eggs were exposed once by painting a spot of contaminant on the shell during the middle third of incubation, when sex determination normally occurs in turtles.

Many more females were hatched in the groups treated by the three compounds than expected based on the strongly male-biased sex ratio of the unexposed eggs.

  Fig 1. Sex ratio (males per female) was altered by each of the contaminants. At the incubation temperature in the experiment, most hatchlings would have been males (control).

After hatching, contamination altered the circulating hormone levels of hatchling turtles. Arochlor and chlordane both suppressed testosterone levels in hatchling males, as did chlordane in hatchling females. Chlordane treatment also suppressed progesterone levels in hatchling females.

Willingham et al. interpret details of the results to suggest that chlordane's impact on sex ratio is a result of anti-androgenic activity by the compound, whereas trans-nonachlor is working as an estrogen mimic. This is important because it illustrates that different hormone disrupting compounds can achieve similar end results (in this case, alterations in sex ratio) via different biochemical mechanisms.





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