New direction of evolutionary study of compound eyes: deep homology of photoreceptors

2016 Fiscal Year Final Research Report

• Project/Area Number: 26650117
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Animal physiology/Animal behavior
• Research Institution: The Graduate University for Advanced Studies
• Principal Investigator: Arikawa Kentaro 総合研究大学院大学, 先導科学研究科, 教授 (20167232)
• Research Collaborator: Perry Michael , JSPS Post-doctoral fellow
• Project Period (FY): 2014-04-01 – 2017-03-31
• Keywords: 複眼 / 視細胞 / 進化 / 発生 / ショウジョウバエ / チョウ類 / 調節因子 / 国際研究者交流

Outline of Final Research Achievements

Compound eyes of many insects consists of two spectrally-heterogeneous ommatidia. The number is three in butterflies and bees, making their eyes spectrally richer. Is this an adaptation for having better color vision in flower-visitors? We addressed this question by comparing the eye development in flies and butterflies. A transcription factor Prospero (Pros) is expressed in a short-wavelength receptor, R7, in all ommatidia in flies. We found Pros is expressed in two cells per an ommatidium in butterflies: R7 seems to be duplicated. Ommatidial heterogeneity is detected in flies by stochastic expression of Spineless (Ss) in R7. In butterflies, two R7-like cells express Ss in three patterns, on/off, on/on and off/off, as if they correspond to three ommatidial types. In fact, butterflies whose ss gene is knocked-out have only the UV-UV type ommatidia. It thus appears that the spectral richness of butterfly eyes is associated with duplication of R7-like cell in the process of adaptation.

Free Research Field

神経行動学、感覚生理学