Biomarkers of reproduction in endangered green sea turtles

Understanding the timing of vitellogenesis is essential for identifying threats to the reproductive success of endangered oviparous vertebrate species, such as sea turtles. We measured concentrations of testosterone (T) and vitellogenin (VTG) in green sea turtles (Chelonia mydas) nesting at Tortuguero, Costa Rica, as biomarkers of ovarian development. Testosterone concentration increased from the first to second month and VTG concentration increased at the third week of sampling. These results show that Tortuguero green sea turtles were still producing both biomarkers early into the nesting season. VTG concentration was negatively correlated with female weight, suggesting that larger females start nesting earlier at Tortuguero and that we may have sampled larger females further into their reproductive cycle.