Establishment of worldwide taxonomic system of the genus Volvox and unveiling the evolution of oogamy

2017 Fiscal Year Final Research Report

• Project/Area Number: 25304012
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Partial Multi-year Fund
• Section: 海外学術
• Research Field: Biodiversity/Systematics
• Research Institution: The University of Tokyo
• Principal Investigator: Nozaki Hisayoshi 東京大学, 大学院理学系研究科(理学部), 准教授 (40250104)
• Co-Investigator(Kenkyū-buntansha): 関本 弘之 日本女子大学, 理学部, 教授 (20281652) ; 三角 修己 山口大学, 大学院創成科学研究科, 准教授 (90583625)
• Co-Investigator(Renkei-kenkyūsha): TSUCHIKANE Yuki 日本女子大学, 理学部, 助教 (20434152)
• Project Period (FY): 2013-04-01 – 2018-03-31
• Keywords: ボルボックス / 分類体系 / 卵生殖 / 進化 / 多様性

Outline of Final Research Achievements

The present study was undertaken to establish a worldwide, objective and natural taxonomic system of the oogamous genus Volvox and unveiling the evolution of oogamy, based on the molecular and asexual and sexual spheroid morphology of Volvox species collected in various localities of the world. Our field and laboratory studies in this research project resulted in the reconstruction of four, monophyletic infrageneric taxa of the genus Volvox. We re-discovered of the ancestral Volvox species from Thailand and resolved its phylogenyetic position. We identified a novel colonial volvocine genus, Colemanosphaera, in obligately anisogamous conjugation between male and female motile gametes occurred outside the female colony (external fertilization during anisogamy). Considering the external obligate anisogamy, oogamy evolution may have been preceded by the transition from external to internal fertilization during anisogamy within the volvocine green algae.

Free Research Field

多様性進化学