2016 Volume 35 Issue 1 Pages 14-21
Blood levels of progesterone (P4), estradiol-17β (E2), calcium (Ca), triglyceride (TG), and total protein (TP) were monitored in a captive female loggerhead turtle throughout a nesting season that included three 13- or 14-d internesting intervals. We observed the turtle’s ovaries to monitor the appearance of shelled eggs, using ultrasonography, and compared the results of blood analyses and ovary observations. The blood P4 level remained low (<0.2 ng/mL), with the exception of three sharp peaks (1.7, 2.2, and 4.2 ng/mL) immediately after the initial three nestings. Eggshell formation occurred immediately after the P4 peaks. The blood Ca level gradually dropped to approximately 3.0 μmol/mL during each eggshell formation period but then recovered to approximately 3.7 μmol/mL prior to the next eggshell formation. The blood E2 level fluctuated between 44 and 299 pg/mL, but with two higher peaks (734 and 419 pg/mL) after eggshell formation in the first and second internesting intervals, respectively. During the nesting season, the blood TG level (initially 20 μmol/mL) showed a stepwise drop to 7.6 μmol/mL, while the blood TP level fluctuated between 57 and 69 mg/mL with no distinct peaks. The periodic cycle of P4 and Ca changes aligned with albumen layer secretion around ovulated follicles immediately after nesting, followed by eggshell calcification in the clutch. The relatively small fluctuations in E2, TG, and TP during the nesting season suggested that lipid deposition and preovulatory follicular development were completed prior to the start of nesting.
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