2018 Fiscal Year Final Research Report

Evolutionary and ecological studies on sperm and reproductive modes in marine sculpins

Research Project

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Project/Area Number	16H04841
Research Category	Grant-in-Aid for Scientific Research (B)
Allocation Type	Single-year Grants
Section	一般
Research Field	Ecology/Environment
Research Institution	Osaka City University
Principal Investigator	Awata Satoshi 大阪市立大学, 大学院理学研究科, 准教授 (60569002)
Co-Investigator(Kenkyū-buntansha)	宗原弘幸北海道大学, 北方生物圏フィールド科学センター, 准教授 (80212249) 古屋康則岐阜大学, 教育学部, 教授 (30273113) 武島弘彦総合地球環境学研究所, 研究部, 外来研究員 (50573086) 柴小菊筑波大学, 生命環境系, 助教 (70533561)
Project Period (FY)	2016-04-01 – 2019-03-31
Keywords	精子 / カジカ科魚類 / 交尾 / 精子競争 / 卵の保護 / 産卵管 / 種間比較 / 種内変異
Outline of Final Research Achievements	Marine sculpins (Cottidae) exhibit diverse reproductive modes and parental behaviors within a family: non-copulatory- and copulatory species with male care, copulatory species with female care and copulatory species with ostracophils. Here, the effects of reproductive modes and the mode of parental care on the evolution of sperm traits (sperm morphology and motility), male genitalia and ovipositor were investigated in 37 sculpin species. (1) We show that sperm traits and male genitalia may have evolved driven by environmental factors independent of the phylogeny in this group. This may be the first report showing the evolution of sperm depending on the copulatory behavior and sperm competition among animals. (2) We also show that ovipositor length and morphology in ostracophilous sculpins could change owing to the host species used (tunicates or sponges) and their size, even among conspecific populations of marine fish with presumably low dispersal ability.
Free Research Field	行動生態学
Academic Significance and Societal Importance of the Research Achievements	本研究の特徴は、脊椎動物を見渡しても他に例を見ないような交尾種と非交尾種を同じ科内に含むカジカ科魚類を材料としたことで、これまで実証が困難であった、「交尾」と「精子競争」が交尾器や精子をどのように進化させてきたかという大きな疑問を解決できた点にある。これらの成果は、脊椎動物や節足動物の陸上への進出に必要であった交尾行動が、動物の配偶子に与えた影響について新規の理解をもたらしたと考えられる。本研究の成果は、生殖生理学、進化学、行動生態学、細胞生物学の分野に新たな展開をもたらすだけでなく、受精という内容上、医学への応用可能性もあり、学術的・社会的な意義は極めて大きい。