2009 Fiscal Year Final Research Report

Ecophysiological investigation of sexual and asexual reproduction of the giant jellyfish Nemopilema nomurai.

Research Project

Project/Area Number	20780138
Research Category	Grant-in-Aid for Young Scientists (B)
Allocation Type	Single-year Grants
Research Field	General fisheries
Research Institution	Hiroshima University
Principal Investigator	IKEDA Hideki Hiroshima University, 大学院・生物圏科学研究科, 研究員 (50452628)
Project Period (FY)	2008 – 2009
Keywords	エチゼンクラゲ / 大量発生 / 再生産 / 生殖巣 / ポリプ / ポドシスト
Research Abstract	The giant jellyfish Nemopilema nomurai reproduces through sexual and asexual processes. In the sexual reproduction, medusae began to develop gonads in their gastric cavity from late June. Oocytes or sperm follicles appeared in the gonads from late July, and the number of oocyte increased and attained several hundred million per a female in November. Maturation of oocytes and sperm follicles rapidly progresses after medusae are physically damaged and are supported by the specialized gonadal epithelial cells which transfer nutrients from the gastric cavity to oocyte and sperm follicle. Asexual reproduction is carried out via dormant podocyst formed by a polyp. Podocyst stores carbohydrates, proteins, and lipids to maintain its dormancy for several years.