Genetic analysis of the microbrain mechanism controlling Drosophila courtship behavior

在昆虫的交配、取食或攻击等行为中，通常会观察到固定的行动模式。然而，人们对遗传背景的本质知之甚少，尽管这些行为通常被称为“基因决定的”或“本能的”。我们发现，果蝇的雄性求偶行为受来自复眼的视觉提示(S)控制。对行为光谱的分析揭示了至少两个截然不同的区域：紫外线或较短波长往往会抑制雄性求爱，而较长波长会促进这种求爱。亚种间的比较分析表明，不同物种对物种间的依赖程度有很大差异。对同一物种内不同品系之间的相互分析发现，雄性基因独占决定了对光的依赖。通过诱变实验，我们发现眼色素基因白色或细胞黏附基因CHOTO的突变导致在光照条件下正常雄性表现出求偶的抑制求偶。白色和毛色的突变都是形态突变，会影响眼睛的光学性质，特别是光感受器的偏振敏感性和/或角度敏感性，而不会对光敏性产生太大影响。因此，我们认为雄性果蝇通过色光和/或偏振光输入来使用视觉信息，果蝇物种对于求爱的视觉控制具有进化上的发散神经机制。

Fixed action patterns are typically observed in the insect behaviors including mating, feeding or aggression. Little is known, however, about the nature of the genetic backgroud although those behaviors are often called as "genetically determined" or "instinctive". We found that the male courtship behavior of Drosophila is controlled by visual cue(s) from the compound eyes. Analysis of the action spectrum revealed at least two spectrall distinct regions : UV or shorter wavelengths tend to suppress the male courtship while longer wavelenghs encourage it. Comparative analysis among melanogaster subspecies group showed that each species has substantially different spectal dependency. Reciprocal analysis between strain within a given species we found that male genotype exclusively determines the light dependency. Through mutagenesis experiments we found that mutaion in the eye-pigent gene white or the cell adhesion gene chaoptic leads to suppression of courtship under light conditions where normal males show courtship. Both mutations in white and chaoptic are morphological mutations that affect the optical property of the eyes, especially the polarization sensitivity and/or the angular sensitivity of the photoreceptors without much affecting photosensitivity. Therefore we propose that males use the visual information through a chromatic and/or polarized light input and that Drosophila species have evolutionary divergent neuronal mechanism for the visual control of courtship.