Hormonal profile of Mediterranean green turtles (Chelonia mydas)

Abstract

The beaches of Turkey are important nesting habitats of Chelonia mydas sea turtles and the determination of their health and disease status is critical in sustaining healthy populations. Limited data currently exist on the hormone values required to determine the status of reproductive capabilities of sea turtles. This study aimed to collect basic data regarding their hormonal profile and set reference limits for the Mediterranean population. Forty-nine free-ranging C. mydas sea turtles were used in the study and were classified into 3 groups according to their age (hatchlings, juvenile, adult). Adult turtles were also grouped according to sex. Adult females were further divided into 3 seasonal groups (summer, spring, and autumn), based on the dates of blood sampling. Plasma testosterone, oestradiol, progesterone, thyroxine (T4), triiodothyronine (T3), thyroid-stimulating hormone (TSH), cortisol, and corticosterone levels were determined by ELISA method. Significantly higher levels were observed in oestrogen (P < 0.001), progesterone (P < 0.001), cortisol (P < 0.05), corticosterone (P < 0.05), T3 (P < 0.05), and T4 (P < 0.01) in the adult turtles when compared with the other groups. The highest levels of oestrogen (280.2 +/- 39.34), progesterone (274.2 +/- 29.4), cortisol (2.26 +/- 0.36), and corticosterone (2.94 +/- 0.53) were determined in the adult female turtles during the spring season. This data could be used to protect the population of this endangered species by taking precautions against diseases via determining their blood hormone levels and taking precautions against reproductive diseases. Further work is required, but this research can expand the knowledge on the basic blood biochemistry of Mediterranean green turtles.