Hormones in the Life History of Sea Turtles

In sea turtles, all of which are thought to show temperature-dependent sex determination (TSD), the developing gonad itself does not appear to give the signal for its own differentiation into a testis or ovary. Additional support for the aromatase-estrogen theory for female differentiation in sea turtles is from the work of Crain et al. and Gross et al., who measured steroids in the chorioallantoic/amniotic fluid of hatchling loggerheads. They found the ratio of estrogen to testosterone is higher in hatchlings raised at warmer temperatures. Sea turtles have proven very useful in hormone studies for two important reasons. First, they are relatively large animals who can therefore give blood easily and repeatedly without suffering physiologically. A second reason for their value in endocrinology and that their commercial use provided pituitaries for biochemical purification of protein hormones.