Figure 1.

Trajectory of gonadal developmental in the red-eared slider turtle (Trachemys scripta). The temperature-sensitive period is highlighted in grey. The bipotential gonad contains primitive sex cords in the medullary region, and germ cells in the outer germinal epithelium. At a female-producing incubation temperature, the primitive sex cords degenerate, while the germ and somatic cells in the cortical region proliferate. At a male-producing incubation temperature, the germ cells migrate into the medullary region where they are enclosed within the developing seminiferous tubules. Arrows indicate the two time periods where estrogen may be acting in ovarian development: during medullary regression and cortical proliferation. E₂ = 17β-estradiol.