Evolutionary ecology of developmental system: Why has situs inversus evolved only in internally fertilizing snails?

• Project/Area Number: 26650161
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Ecology/Environment
• Research Institution: Shinshu University
• Principal Investigator: ASAMI Takahiro 信州大学, 学術研究院理学系, 教授 (10222598)
• Project Period (FY): 2014-04-01 – 2016-03-31
• Project Status: Completed (Fiscal Year 2015)
• Budget Amount: ¥4,160,000 (Direct Cost: ¥3,200,000、Indirect Cost: ¥960,000); Fiscal Year 2015: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000); Fiscal Year 2014: ¥3,510,000 (Direct Cost: ¥2,700,000、Indirect Cost: ¥810,000)
• Keywords: 左右性 / 螺旋卵割 / 鏡像進化

Outline of Final Research Achievements

In bilaterian metazoa, mutation for left-right reversal is associated with an increased probability of early developmental defect and reduces survival. This purifying selection constrains the evolution of situs inversus. In contrast, left-right reversal of primary asymmetry has repeatedly evolved in gastropods that copulate for reproduction (i.e. internally fertilize). The present study disclosed that mutations in wild populations of terrestrial gastropods generate continuous variation in the degree of left-right polarity in spiral cleavage by their maternal effect.