Daily Changes in the Blood Levels of Two Steroids and Other Biochemicals Related to Vitellogenesis and Eggshell Formation during Internesting Intervals in a Captive Female Loggerhead Turtle

Abstract: 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...