Experiment 1 Behaviour - Females.dat from Interactions between the sexual identity of the nervous system and the social environment mediate lifespan in <i>Drosophila melanogaster</i>.

Sex differences in lifespan are ubiquitous, but the underlying causal factors remain poorly understood. Inter- and intrasexual social interactions are well known to influence lifespan in many taxa, but it has proved challenging to separate the role of sex-specific behaviours from wider physiological differences between the sexes. To address this problem, we genetically manipulated the sexual identity of the nervous system—and hence sexual behaviour—in <i>Drosophila melanogaster</i>, and measured lifespan under varying social conditions. Consistent with previous studies, masculinization of the nervous system in females induced male-specific courtship behaviour and aggression, while nervous system feminization in males induced male–male courtship and reduced aggression. Control females outlived males, but masculinized female groups displayed male-like lifespans and male-like costs of group living. By varying the mixture of control and masculinized females within social groups, we show that male-specific behaviours are costly to recipients, even when received from females. However, consistent with recent findings, our data suggest the courtship expression to be surprisingly low cost. Overall, our study indicates that nervous system-mediated expression of sex-specific behaviour <i>per se</i>—independent of wider physiological differences between the sexes, or the receipt of aggression or courtship—plays a limited role in mediating sex differences in lifespan.寿命的性别差异普遍存在，但背后的潜在因果机制仍尚不明确。异性间与同性间的社会互动在诸多生物类群中均已被证实会影响寿命，然而要将性别特异性行为的作用与两性间更广泛的生理差异区分开来，却颇具挑战。为解决这一问题，我们在黑腹果蝇（Drosophila melanogaster）中通过遗传操控神经系统的性别身份，进而改变其性行为，并在不同社会条件下测定其寿命。与既往研究结果一致，雌性神经系统的雄性化会诱导出雄性特有的求偶行为与攻击行为，而雄性神经系统的雌性化则会引发雄性间求偶行为并降低攻击水平。对照组雌性的寿命长于雄性，但雄性化雌性群体则表现出类似雄性的寿命，以及类似雄性的群居生存代价。通过在社会群体中调整对照组雌性与雄性化雌性的混合比例，我们发现，即便雄性特有的行为来自雌性个体，对行为接收者而言仍带有适应性代价。不过，与近期研究结果一致，我们的数据显示求偶行为的表达竟只需极低的适应性代价。综上，本研究表明，由神经系统介导的性别特异性行为表达本身——独立于两性间更广泛的生理差异，亦或接收攻击或求偶行为的经历——在介导寿命的性别差异方面作用有限。