Molecular regulation of lifespan extension in fertile ant workers.

The evolution of sociality in insects caused a divergence in lifespan between reproductive and non-reproductive castes. Ant queens can live for decades, while most workers survive only weeks to a few years. In most organisms, longevity is traded-off with reproduction, but in social insects, these two life-history traits are positively linked. Once fertility is induced in workers, e.g. by queen removal, worker lifespan increases. The molecular regulation of this positive link between fecundity and longevity and generally the molecular underpinnings of caste-specific senescence are not well understood. Here, we investigate the transcriptomic regulation of lifespan and reproduction in fat bodies of three worker groups in the ant Temnothorax rugatulus. In a long-term experiment, workers that became fertile in the absence of the queen showed increased survival and upregulation of genes involved in longevity and fecundity pathways. Interestingly, workers that re-joined their queen after months exhibited intermediate ovary development, but retained a high expression of longevity and fecundity genes. Strikingly, the queen's presence causes a general downregulation of genes in worker fat bodies. Our findings point to long-term consequences of fertility induction in workers, even after re-joining their queen. Moreover, we reveal longevity genes and pathways modulated during insect social evolution. This article is part of the theme issue 'Ageing and sociality: why, when and how does sociality change ageing patterns?'