Odonata species display a remarkable diversity of colour patterns, including intrasexual polymorphisms. In the damselfly (Ischnura senegalensis), the expression of a sex-determining transcription factor, the doublesex (Isdsx) gene is reportedly associated with female colour polymorphism (CP) (gynomorph for female-specific colour and andromorph for male-mimicking colour). Here, the function of Isdsx in thoracic coloration was investigated by electroporation-mediated RNA interference (RNAi). RNAi of the Isdsx common region in males and andromorphic females reduced melanization and thus changed the colour pattern into that of gynomorphic females, while the gynomorphic colour pattern was not affected. By contrast, RNAi against the Isdsx long isoform produced no changes, suggesting that the Isdsx short isoform is important for body colour masculinization in both males and andromorphic females. When examining the expression levels of five genes with differences between sexes and female morphs, two melanin-suppressing genes, black and ebony, were expressed at higher levels in the Isdsx RNAi body area than a control area. Therefore, the Isdsx short isoform may induce thoracic colour differentiation by suppressing black and ebony, thereby generating female CP in I. senegalensis. These findings contribute to the understanding of the molecular and evolutionary mechanisms underlying female CP in Odonata.

蜻蜓目物种表现出显着的颜色模式多样性，包括性内多态性。据报道，在豆娘 ( Ischnura senegalensis ) 中，一种性别决定转录因子的表达， doublesex ( Isdsx ) 基因与雌性颜色多态性 (CP) 有关（雌性型代表女性特有的颜色，雄型型代表模仿雄性的颜色）。在此，通过电穿孔介导的 RNA 干扰 (RNAi) 研究了Isdsx在胸部着色中的功能。雄性和雌雄同体雌性中Isdsx共同区域的 RNAi 减少了黑色化，从而将颜色模式改变为雌雄同体雌性的颜色模式，而雌雄同体的颜色模式不受影响。相比之下，针对Isdsx长异构体的 RNAi 没有产生任何变化，这表明Isdsx短异构体对于雄性和雌性雌性的体色男性化都很重要。当检查性别和雌性形态之间存在差异的 5 个基因的表达水平时，两种黑色素抑制基因（黑色和乌木）在Isdsx RNAi 身体区域中的表达水平高于对照区域。因此， Isdsx短亚型可能通过抑制黑色和乌木色来诱导胸部颜色分化，从而在塞内加尔伊蚊中产生雌性CP。这些发现有助于理解蜻蜓目雌性 CP 的分子和进化机制。