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

• Project/Area Number: 17510195
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Resource conservation science
• Research Institution: Gifu University
• Principal Investigator: DOI Osamu Gifu University, Faculty of Applied Biological Sciences, Professor (60180212)
• Project Period (FY): 2005 – 2007
• Project Status: Completed (Fiscal Year 2007)
• Budget Amount: ¥3,770,000 (Direct Cost: ¥3,500,000、Indirect Cost: ¥270,000); Fiscal Year 2007: ¥1,170,000 (Direct Cost: ¥900,000、Indirect Cost: ¥270,000); Fiscal Year 2006: ¥1,100,000 (Direct Cost: ¥1,100,000); Fiscal Year 2005: ¥1,500,000 (Direct Cost: ¥1,500,000)
• Keywords: loggerhead sea turtle / fertilized egg / sex steroid hormone / incubation period / clouded eggshell / 移植

Research Abstract

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.

Research Products

• [Journal Article] アカウミガメにおける移植した受精卵の孵化率低下原因の解明と産卵生理に関する研究 (2006)
  • Author(s): 土井 守, 寺嶋淳美, 加藤隆司, 福岡敏夫, 市川憲平, 増田 修, 後藤 清, 松沢慶将
  • Journal Title: 第14回希少動物人工繁殖研究会議資料集 Pages: 25-26
• [Presentation] アカウミガメの胚発生の進行と産卵生理に関する研究 (2007)
  • Author(s): 田中浩之, 寺嶋淳美, 加藤隆司, 福岡敏夫, 市川憲平, 増田 修, 後藤清, 松沢慶将, 楠田哲士, 土井 守
  • Organizer: 第15回希少動物人工繁殖研究会議
  • Place of Presentation: 神戸市立王子動物園
  • Year and Date: 2007-06-07
  • Description: 「研究成果報告書概要(和文)」より
• [Presentation] Ontogenetic and endocrinological studies in the loggerhead sea turtle (2007)
  • Author(s): Tanaka, H., Terashima, A., Kato, T., Fukuoka, T., Ichikawa, K., Masuda, O., Goto, K., Matsuzawa, K., Kusuda, S., Doi, O
  • Organizer: Proceeding of the 15th Annual Meeting in Japanese Study Group on Artificial Reproduction of Endangered Animals
  • Year and Date: 2007-06-07
  • Description: 「研究成果報告書概要(欧文)」より
• [Presentation] Elucidation of the most important cause of lower hatching rate in case of transplanted fertilized eggs and endocrinological study in the loggerhead sea turtle (2006)
  • Author(s): Doi, O., Terashima, A., Kato, T., Fukuoka, T., Ichikawa, K., Masuda, O., Goto, K., Matsuzawa, K
  • Organizer: Proceedings of the 14th Annual Meeting in Japanese Study Group on Artificial Reproduction of Endangered Animals
  • Year and Date: 2006-06-27
  • Description: 「研究成果報告書概要(欧文)」より
• [Presentation] アカウミガメにおける移植した受精卵の孵化率低下原因の解明と産卵生理に関する研究 (2005)
  • Author(s): 土井 守, 寺嶋淳美, 加藤隆司, 福岡敏夫, 市川憲平, 増田 修, 後藤 清, 松沢慶将
  • Organizer: 第14回希少動物人工繁殖研究会議
  • Place of Presentation: 大阪市天王寺動物園
  • Year and Date: 2005-06-27
  • Description: 「研究成果報告書概要(和文)」より
• [Presentation] アカウミガメの卵殻構造の組織学的変化と卵殻内培養法による胚発生に関する研究 (2005)
  • Author(s): 土井 守, 佐藤宏佳, 杉山智香, 亀崎直樹, 松沢慶将, 後藤 清, 小久保信一, 福岡敏夫, 大池辰也, 黒柳賢治, 栃本武良, 湯浅義明, 市川憲平, 三木 徹, 増田 修, 津田英治, 清水邦一, 脇本久義, 多田雄作
  • Organizer: 第13回希少動物人工繁殖研究会議
  • Place of Presentation: 東京都多摩動物公園
  • Year and Date: 2005-06-13
  • Description: 「研究成果報告書概要(和文)」より
• [Presentation] Ultrastructural histological study of eggshell and development in culture of the embryo in the loggerhead sea turtle (2005)
  • Author(s): Doi, O., Sato, H., Sugiyama, T., Kamezaki, N., Matsuzawa, K., Goto, K., Kokubo, S., Fukuoka, T., Oike, T., Kuroyanagi, K., Tochimoto, T., Yuasa, Y., Ichikawa, K., Mild, T., Masuda, O., Tsuda, E., Shimizu, K., Wakimoto, H., Tada, Y
  • Organizer: Proceedings of the 13th Annual Meeting in Japanese Study Group on Artificial Reproduction of Endangered Animals
  • Year and Date: 2005-06-13
  • Description: 「研究成果報告書概要(欧文)」より