Raw data T. rugatulus from Queen loss increases worker survival in leaf-cutting ants under paraquat-induced oxidative stress

Longevity is traded off with fecundity in most solitary species, but the two traits are positively linked in social insects. The most fecund individuals (queens and kings) live longer than the non-reproductive individuals, the workers. In many species, workers may become fertile following queen loss, and recent evidence suggests that worker fecundity extends worker lifespan. We postulated that this effect is in part due to improved resilience to oxidative stress, and tested this hypothesis in three Myrmicine ants: Temnothorax rugatulus, and the leaf-cutting ants Atta colombica and Acromyrmex echinatior. We removed the queen from colonies to induce worker reproduction and subjected workers to oxidative stress. Oxidative stress drastically reduced survival, but this effect was less pronounced in leaf-cutting ant workers from queenless nests. We also found that, irrespective of oxidative stress, outside workers died earlier than inside workers did, likely because they were older. Since At. colombica workers cannot produce fertile offspring, our results indicate that direct reproduction is not necessary to extend the lives of queenless workers. Our findings suggest that workers are less resilient to oxidative stress in the presence of the queen, and raise questions on the proximate and ultimate mechanisms underlying socially mediated variation in worker lifespan.This article is part of the theme issue ‘Ageing and sociality: why, when and how does sociality change ageing patterns?’.

在绝大多数独居物种中，寿命与繁殖力存在生活史权衡，但在社会性昆虫中，这两种性状呈正相关。繁殖力最强的个体（蚁后与雄蚁）寿命长于非繁殖的工蚁。在诸多蚂蚁物种中，蚁后缺失后工蚁可恢复繁殖能力，近期研究表明工蚁的繁殖能力可延长其自身寿命。我们推测该效应部分源于抗氧化应激（oxidative stress）能力的提升，并在三种蚁亚科蚂蚁中验证了这一假说：红扁胸切叶蚁（Temnothorax rugatulus）、哥伦比亚切叶蚁（Atta colombica）以及棘刺顶切叶蚁（Acromyrmex echinatior）。我们通过移除蚁后诱导工蚁启动繁殖，并对工蚁施加氧化应激处理。氧化应激会大幅降低工蚁存活率，但该效应在蚁后缺失蚁巢的切叶蚁工蚁身上表现得并不显著。我们还发现，无论是否施加氧化应激，外勤工蚁的死亡时间均早于内勤工蚁，这大概率是因为外勤工蚁年龄更大。由于哥伦比亚切叶蚁的工蚁无法产生可育后代，我们的研究结果表明，延长蚁后缺失工蚁寿命并不需要其直接进行繁殖。我们的研究结果表明，当蚁后存在时，工蚁的抗氧化应激能力更弱，该发现也为探究社会因素介导的工蚁寿命差异的近因与远因机制提出了新的科学问题。本文属于“衰老与社会性：社会性为何、如何以及何时改变衰老模式？”专题特刊的一部分。