In most living organisms, there is a relationship between reproduction and lifespan. This is largely because animals that have many offspring often commit significant nutritional and metabolic resources to reproduction at the expense of their own longevity.
However, ants and some other insects are an exception to this pattern. In any ant colony, reproductive activity is limited to a single or a few queens. Reproductive queens can live for decades – the equivalent of many lifetimes of a colony’s non-reproductive workers – and lay millions of eggs.
In some species of ants, such as Harpegnathos saltator, workers can change castes and become reproductive pseudo-queens, or gamergae, when a queen dies or is removed from the colony.
Despite being born as workers, gamergadae can live up to five times longer than their ancient counterparts. Additionally, gamergadae can revert to their (reverted) worker status if incorporated into a colony with an established worker caste, reverting to a short-lived.
How this reproductive longevity is regulated in these animals, particularly during active reproduction, has long been a biological mystery.
An ant. (Photo: Amazings/NCYT)
To assess the relationship between reproduction and longevity, Hua Yan of New York University in the United States and colleagues performed bulk RNA sequencing in tissues relevant to reproduction and metabolism of worker H. saltator ants, gamergated and reverted, comparing gene expression during caste change.
As expected, Yan’s team found that insulin was upregulated to favor oogenesis in gamergadae, although this did not lead to shorter lifespans, as it does in other animals. The study authors found that increased insulin induces ovarian development in gamergae, which in turn results in the production of the insulin suppressor protein Imp-L2 in the MAPK branch of the insulin signaling pathway.
This anti-insulin protein blocks signaling in the other main branch of the insulin signaling pathway responsible for aging control, AKT. According to the study authors, decreased AKT activity may allow H. saltator queens and pseudoqueens to live longer.
The study is titled “Insulin signaling in the long-lived reproductive caste of ants.” And it has been published in the academic journal Science. (Source: AAAS)