Among butterflies, adulthood usually lasts only a matter of weeks — a time for feeding, mating, and laying eggs, after which the body rapidly declines. However, species of the genus Heliconius from the tropical forests of Central and South America live on average three times longer than their closest relatives, and individual specimens reach 348 days. At the same time, some of them, such as Heliconius hecale, show almost no physiological deterioration with age.
A study published in Nature Communications and conducted under the leadership of the University of Bristol together with the Smithsonian Tropical Research Institute in Panama compared species of the tribe Heliconiini. The scientists measured lifespan, body mass, and grip strength — an indicator of muscle function. Even when Heliconius hecale were deprived of pollen, their main source of nutrients, they still lived significantly longer than Dryas iulia, which does not feed on pollen. The difference in maximum lifespan between the species reached 25 times — 348 days versus 14.
Pollen undoubtedly provides an advantage: it allows the body to be sustained longer than nectar does. But the experiments showed that nutrition does not explain everything. Heliconius hecale maintained body mass and grip strength throughout their lives, whereas Dryas iulia lost a quarter of their strength after just five weeks. Baseline mortality in the long-lived species turned out to be lower, and the rate of aging slower. This points to evolutionary changes in the biology of the insects themselves.
The close kinship of species with sharply differing lifespans makes Heliconius a convenient model. Instead of comparing organisms far removed from each other, researchers can look for specific genetic and physiological differences that slow the wear of tissues. The next step is to identify which mechanisms allow these butterflies to maintain muscle performance and stable body mass for so long.
The discovery underscores how plastic the aging process can be even within a single group of insects. If it becomes possible to understand which biological traits ensure delayed aging in Heliconius, this will provide new reference points for studying how organisms in general control the rate of wear and the maintenance of functions.
