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Current Herpetology
Abstract
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. 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.
We express our deep gratitude to H. Miyahara, director of the Okinawa Churaumi Aquarium, for providing us with valuable suggestions and comments on this study. We are grateful to the staff of the Okinawa Churashima Foundation for their assistance with blood sampling and ovary observation through ultrasonography. We also thank Dr. M. Nakamura of the Okinawa Churashima Foundation for advice regarding manuscript preparation. We also thank the anonymous reviewers for constructive suggestions that helped us improve the manuscript. The Okinawa Prefecture provided permits for the capture and holding of turtles based on the Fishery Acts of Japan.
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