Evolution is all over the place in terms of lifespans, which range from the duration of a quick phone call to animals that may be older than recorded history.
Mayflies live for just 5 minutes; Greenland sharks are older than most countries; glass sponges may predate widespread agriculture, and amputated bits of sea cucumber (yes, the animal that 'rents' its anus as an apartment for fish) appear to remain active indefinitely.
Now, researchers have just revealed an incredible variation in the lifespans of closely related butterflies, including a species that lives 25 times longer than others of its kin.
Butterflies perform some of nature's most awe-inspiring acts. Every year, many millions of monarchs migrate from Mexico to the US West Coast, covering the landscapes in a fluttering, black-and-orange wallpaper.
Similarly, painted lady butterflies can cross the Atlantic Ocean, covering 4,200 kilometers (2,600 miles) in about a week, putting historical colonists to shame.
Yet, like many of nature's most spectacular sights, butterflies are ephemeral, typically living for only a couple of weeks.
To better understand the factors controlling insect longevity, researchers compiled the maximum reported lifespans of 10 members of the Heliconiini tribe, comprising dozens of butterfly species, using data from field studies, public butterfly houses, and mark-release-recapture programs.
They found an astounding variation in the lifespans of these close-kin butterflies, ranging from 14 days for the species Dione juno (named for a Greek and a Roman goddess), to 348 days for the Heliconius hewitsoni.
This is the highest variation ever recorded in non-fish animals with such close kinship, offering an environmental-ancestral enigma.
Perhaps their long lives are due to a unique diet: butterflies of the Heliconius genus are the only ones known to consume pollen as adults.
Accordingly, all the longest-lived butterflies in the study were of the pollen-partaking persuasion, with an average maximum lifespan of around 177 days. For comparison, the non-pollen-consumers displayed an average of approximately 58 days.
Overall, Heliconius exhibited longer median and maximum lifespans, lower baseline mortality, slower rates of aging, and, perhaps amusingly, stronger grip strength in the Lepidopteran version of a deadlift.
The researchers also conducted a pollen-manipulation experiment. Surprisingly, when placed on a pollen-deprived diet, the Heliconius hecale butterfly still outlived a species from a different genus, Dryas iulia, suggesting that heritable factors – and not just diet – play a role.
Still, since pollen is loaded with beneficial fats and amino acids, it may boost the butterflies' immune defenses and energy storage capabilities.
However, D. iulia did not gain these benefits when placed on a pollen-inclusive diet, suggesting that Heliconius have gained adaptations that allow them to exploit the diverse nutritional benefits of pollen.
Related: Many Butterflies Have a Second 'Head' – This Could Be Why
The 348-day lifespan of H. hewitsoni is the longest recorded in scientific literature. Yet the researchers did one better, presenting the non-Heliconius butterfly, Myscelia cyaniris, as the most long-lived butterfly, with a reported 380-day maximum lifespan.
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A Heliconius erato, or red postman, with a proboscis full of nutritious, fat-and-amino-acid-laden pollen. (Sebastián Mena) Further study should help disentangle the many factors related to increased longevity and weigh the influence exhibited by individual butterflies with anomalously long lives. For this reason, maximum lifespan may be a problematic measure because it's highly affected by sample size.
And, since real science often proves stranger than fiction, it's not out of the realm of feasibility that such research may eventually inform human-based therapies to improve overall well-being and squeeze another year or two out of our already increasing life expectancies.
This research is published in Nature Communications.