Elucidation of the most important muse of lower hatching rate in case of transplanted fertilized eggs in the wild loggerhead sea turtle

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In the loggerhead sea turtle (Caretta earetta), the embryo adhesion to eggshell membrane and a part of the clouded eggshell were driven from the top of fertilized eggs during incubation. However, embryos did not always adhere to the top of eggshells under the normal incubation condition, and some embryo in 15-day incubation was observed to develop in the bottom of eggs. From this result, it was found that sea turtle embryos do not necessarily become attached to the inner surface on top of eggshell. Moreover, sea turtle eggs are sensitive to turning shortly after laying, and fertilized eggs of the nest that must be relocated under a bad condition for incubation should be moved within 12 hours of laying or after about 40 days of incubation time. With data logger, the temperature and moisture of the sand at wild beach were measured and degree-days was calculated. The sand temperature and moisture was closely related to the precipitation in nature, and total temperature must be over 1800 degrees for hatching. On the other hand, serum estradiol-17β (E2) concentration in female and testosterone (T) concentration in male increased when water temperature declined in captivity. That is, serum sex steroid hormone (except for serum progesterone) increased at September to February (the increased period in water temperature), and decreased from May to July (the decreased period). Female serum progesterone concentration increased at February to May just before the onset of laying in nature. In this study, the timing and method of transplantation for sea turtle egg in circumstances where eggs can not be expected to hatching after laying, and endocrinological and reproductive physiology of the loggerhead sea turtle were able to be clarified. These results of this study may be helpful in protecting the loggerhead sea turtle from extermination at Japanese beach.