The Starset SocietyBy: Rhodilee Jean Dolor
The average lifespan of most butterflies is just two to four weeks, but a new study reveals that a neotropical genus of these colorful insects can live nearly a year, or up to 25 times longer than some of its relatives.
Heliconius Butterflies
In a new study published in the journal Nature Communications on June 16, researchers took a closer look at the butterflies belonging to the Heliconius genus.
Also known as the longwings or heliconians, these butterflies from Central and South America are known for mimicking the wing patterns of their unpalatable relatives to avoid getting eaten by predators.
They are also among the longest-lived butterflies ever documented. Researchers said that these flutterers are not just breaking the norm in butterfly lifespan. They may also hold the key to unveiling the secrets that may extend human longevity.
According to study researcher Jessica Foley, from the School of Biological Sciences of the University of Bristol in the UK, and colleagues, Heliconius butterflies, on average, can live about three times longer than closely-related species.
The gap is particularly notable between Heliconius hewitsoni, which can survive up to 348 days, and Dione juno–a close relative that can only last 14 days. The researchers said that the maximum lifespan of the two species is marked by a 25-fold difference.
Defying Aging
Foley and colleagues also found that the Heliconius hecale species have little to no measurable physical decline as they age. Using a device called “the pullinator”, the team carried out a grip-strength test to measure age-related decline in the butterflies.
“We placed this on a lab balance, zeroed the balance, and then gently held a butterfly by the wings and lowered it until it grasped the perch,” Foley explained to CNN. “We then tugged until it let go — but as the butterfly tugged, the balance would drop negative, and we could use the maximum negative reading as an indication of how much weight the butterfly could carry before it let go.”
The researchers found that older H. hecale butterflies performed just as well as the younger individuals. They also showed no obvious signs of deterioration.
“What makes them particularly remarkable is that they appear to have evolved not only longer lifespans, but also slower aging. This allows them to live significantly longer than closely related species from which they diverged relatively recently in evolutionary time,” Foley said in a statement.
Pollen And Proline
Foley and colleagues also probed on the popular idea that the extraordinary lifespan of Heliconius stems from their diet. These lepidopterans consume pollen in adulthood.
Most butterfly species primarily rely on nectar but the Heliconius butterflies actively collect and ingest pollen as adults. Scientists suspect that this unusual feeding ability could be the reason why these insects have long lives. For instance, the Heliconius species that consume pollen live longer than their kins that do not feed on pollen.
The researchers think that pollen helps Heliconius butterflies fight age-related physiological decline. They noted that the pollen of Psiguria, which the Heliconius species involved in the study primarily fed on, is rich in the amino acid proline.
Proline plays a critical role in energy storage in insect muscle and haemolymph, the body fluid inside arthropod bodies that transport nutrients and oxygen to tissues.
The researchers observed that while pollen-fed Heliconius hecale maintained their body mass and muscle function with age, those deprived of pollen saw steep decline in body mass. Foley and her team explained how this can help the butterflies live longer.
“[I]mproved physiological condition may have ecological relevance for fitness in pollen-fed Heliconius, conferring advantages in competition for resources, or through enhanced predator avoidance, as reflected in their reduced baseline mortality,” they wrote in their study.
Evolutionary Factor
The researchers also compared the effect of pollen deprivation on Heliconius and its non-pollen-feeding relative, Dryas iulia. They observed that even without dietary pollen, the Heliconius species still lived longer.
“The results of the pollen-manipulation experiment show that while H. hecale and D. iulia show similar baseline mortality, H. hecale has evolved a slower rate of aging, resulting in the observed lifespan extension. This slowed rate is maintained even under pollen-deprivation, suggesting that this parameter is unrelated to the short-term plastic effects of adult diet.”
The results showed that aside from developing the preference to feed on pollen, Heliconius also evolved the physiological adaptations needed to fully exploit the nutritional benefits of its diet. The researchers said that this adaptation did not happen to D. iulia and possibly to other non-pollen feeding butterflies.
“The remarkable lifespan increase in Heliconius has been linked to the evolution of adult pollen-feeding in this genus, which is unique among butterflies,” Foley and colleagues reported.
“This dietary innovation has been linked to a suite of other behavioural, neuroanatomical, and physiological traits in Heliconius that are not present in other non-pollen-feeding Heliconiini. These include increased investment in neural structures supporting learning and memory and more stable long-term visual memories.”
Implication on Human Longevity
Jaret Daniels, an entomologist at the University of Florida who was not involved in the study, said that the mechanisms behind aging are often similar across the animal kingdom. Thus, the extraordinary lifespan of the Heliconius butterfly may be used to advance studies on longevity, which can have potential implications on human longevity.
Diet is also linked to longer lifespan in humans. Experts have long vouched for good nutrition in promoting longevity. Healthy food can protect against cellular damage and support immune cells to help with body repair. Meanwhile, food products that are high in sugar and unhealthy fats can make the body more vulnerable to damage.
“The exciting implication of this lifespan extension is that it provides a powerful opportunity to identify the mechanisms that underpin longevity. By comparing long-lived Heliconius butterflies with their short-lived relatives, we have a natural evolutionary experiment that can help reveal how lifespan is extended, making them a highly promising new model for research into the biology of aging and longevity,” the researchers said.
