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

在红海龟（Caretta earetta）孵化过程中，胚胎附着在卵壳膜上，部分混浊的蛋壳从受精卵顶部脱落。但在正常孵化条件下，胚胎并不总是附着在蛋壳的顶部，在孵化15天后，观察到一些胚胎在蛋的底部发育。根据该结果，发现海龟胚胎不一定附着在蛋壳顶部的内表面上。此外，海龟蛋在产下后不久便容易翻面，如海龟蛋的巢内受精卵在环境恶劣的情况下必须迁移以进行孵化，应在产下后12小时内或孵化期约40天后迁移。利用数据记录仪对野外海滩的温度和湿度进行了测量，并计算了度日数。沙温、沙湿与自然界降水量密切相关，总温必须在1800 ℃以上才能孵化。另一方面，随着水温的降低，雌鱼血清雌二醇（E2）和雄鱼血清睾酮（T）浓度升高。即血清性类固醇激素（除孕酮外）在9 ~ 2月（水温升高期）升高，5 ~ 7月（水温下降期）降低。雌性血清孕酮浓度增加，在2月至5月之前的性质奠定了发病。本研究对产蛋后不能期望孵化的情况下海龟卵移植的时机和方法以及红海龟的内分泌和生殖生理进行了研究。本研究结果可为保护日本海滩的红海龟免于灭绝提供参考。

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.