2013 Fiscal Year Final Research Report

Sterilization of fish by high temperature

Research Project

Project/Area Number	23658166
Research Category	Grant-in-Aid for Challenging Exploratory Research
Allocation Type	Multi-year Fund
Research Field	General fisheries
Research Institution	Meio University (2013) University of the Ryukyus (2011-2012)
Principal Investigator	NAKAMURA Masaru 名桜大学, 公私立大学の部局等, 研究員 (10101734)
Co-Investigator(Kenkyū-buntansha)	HIRAI Toshiaki 帝京科学大学, 生命環境学部, 教授 (30238331)
Project Period (FY)	2011 – 2013
Keywords	魚類 / 不妊化 / 生殖腺 / 卵巣 / 精巣 / 生殖細胞
Research Abstract	Juveniles of the Mozambique tilapia, were reared from 3 days after hatching at a high temperature (37 degree centigrade) for 50 days. The gonads of all individuals were sterile. Sterile females did not display sexual behavior or exhibit female nuptial coloration, Histological analysis revealed the absence of all stages of spermatogenic germ cells from the testes of the heat-treated males; however, structures within the layer of epithelial cells lining the efferent ducts were observed to be actively secreting sperm fluid into the ducts, as also seen in the mature testes of normal males. The sterilized males nonetheless displayed male nuptial coloration, actively dug spawning nests, and mated with normal mature females. However, females mated with these males initially brooded their eggs normally but released them prematurely at 4 to 5 days. All the released eggs were unfertilized, and all were dead.