Genetic analysis of the microbrain mechanism controlling Drosophila courtship behavior

在昆虫的交配、取食、攻击等行为中，通常可以观察到固定的行为模式。然而，尽管这些行为通常被称为“遗传决定的”或“本能的”，但对遗传背景的性质知之甚少。我们发现果蝇的雄性求偶行为是由复眼的视觉线索控制的。对雄性求偶行为的光谱分析表明，至少有两个光谱区：紫外线或短波长的光抑制雄性求偶行为，而长波长的光促进雄性求偶行为。在一个给定的物种内，我们发现，雄性基因型之间的相互分析完全决定了光的依赖性。通过突变实验，我们发现，在眼睛色素基因白色或细胞粘附基因混沌的突变导致抑制求爱在光照条件下，正常男性显示求爱。白色和混沌的突变都是形态学突变，其影响眼睛的光学性质，特别是光感受器的偏振灵敏度和/或角灵敏度，而不太影响光敏性。因此，我们建议，男性使用的视觉信息，通过彩色和/或偏振光输入和果蝇物种进化发散的神经元机制的视觉控制求爱。

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.