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