In numerous animal species, having more than one offspring is related to a shorter lifetime. The distribution of food and metabolic resources is the trade-off between longevity and fertility. For queen ants, however, this is not the case. Researchers from New York University contend that an insulin-suppressing protein could be the key to the ant's longevity. This study published in the Science journal may shed light on how other species age.

(Photo: Kalyan Varma/via Wikimedia Commons)
Jumping Ants

Egg Production and Ants' Life Span

For animals, it takes a lot of energy and more food to produce eggs because the amount of insulin rises. However, the insulin pathway's enhanced activity, which is necessary for reproduction, causes most animals to live shorter lives. Contrarily, food restrictions lengthen life by lowering insulin levels. In fact, several scientists are looking into whether fasting lengthens life, as published in Nature.

The trade-off between reproduction and longevity is not true in ants. Because even though they have the same genome, their queens live considerably longer than worker ants.

A queen in a species like the black garden ant can produce one million eggs during her lifetime and survive for 30 years. However, its sterile worker sisters only have a one-year lifespan. Queens of the jumping ant species Harpegnathos saltator, the subject of this study, normally live for five years, while workers only last seven months.

Harpegnathos Saltator Ants Caste Switching

When a colony's Harpegnathos queen dies, a strange event happens. The female worker ants compete against one another using their antennae to select who will succeed the present queen. While still residing in the smaller body of a worker, the duel winners alter their caste in the ant society and become pseudoqueens, also known as gamergates.

Pseudoqueens extend their life span from seven months to four years and develop queen-like traits, such as producing eggs. However, if another queen steps in to take their position, they revert to worker status, stop making eggs, and have their lifespan cut to seven months.

Harpegnathos ants, which undergo reversible caste switching from workers to pseudoqueens that dramatically extends both their lifespan and capacity for reproduction, offer a special opportunity to study how aging and reproduction can be disconnected, according to the study's co-senior author Claude Desplan, Silver Professor of Biology and Neural Science at NYU.

ALSO READ:  How Do Ants Pass Knowledge to Each Other? Robotics Have the Answer

Insulin Suppresses the Pathway that Regulates Aging

The researchers examined tissue samples from workers and pseudoqueens using bulk RNA-sequencing. They concentrated on ant organs involved in metabolism and reproduction, such as the brain, fat body (an insect's liver), and ovaries. 

They discovered that to create eggs, the ants that changed from worker to pseudoqueen produced more insulin in their brains. One of the two major branches of the insulin signaling system, MAPK, which regulates metabolism and egg development, is activated due to elevated insulin levels.

Pseudoqueens' elevated insulin levels trigger ovary development, producing Imp-L2, a protein that suppresses insulin. Imp-L2 inhibits the other major branch of the insulin signaling pathway, AKT, whose increasing activity shortens life span and regulates aging.

Research Impact on Related Studies

According to Hua Yan, the study's co-first author and a former postdoctoral researcher at NYU Grossman School of Medicine, the interaction, which developed in ants and maybe in other insects, may be responsible for the extraordinary longevity and a large number of offspring in reproductive ants.

Desplan continued by saying that their work is an important example of the value of employing the right model systems when posing important biological queries. For instance, most longevity treatments in animals like mice or flies typically increase their lifespans by 10% to 20%. Ants' extraordinary 500% increase in a lifetime makes studying them considerably more effective.

RELATED ARTICLE: Ants Do Not Eat Leaves: They Use Them To Grow Fungus Garden For Food And Space

Check out more news and information on Medicine and Health in Science Times.