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While hiking through the rainforests of northern Vietnam, scientists unexpectedly discovered wasp nests that glow fluorescent green beneath ultraviolet light.
The nests, which resemble a cluster of hexagonal cells, were built by several species of paper wasps, all belonging to the genus Polistes. Wasps seal the underside of hexagonal cells with silky fiber cocoon caps, which protect the larvae growing in the nest. And for reasons still unknown, these cocoon caps emit a strong greenish-yellow glow when exposed to UV light between 360 and 400 nanometers in wavelength.
“We were very surprised to find such a strongly fluorescent biomaterial,” lead author Bernd Schöllhorn, professor of chemistry at the University of Paris, told Live Science in an email.
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The team initially set out to discover fluorescent insects unknown in tropical rainforests, so they were equipped with UV LED torches. “We weren’t looking for wasp nests in particular,” said Schöllhorn. “To our knowledge, this phenomenon has not been observed in the past, neither by scientific researchers nor by any photographer.”
When exposed to white light, the caps of the nest cocoons appear crisp white. Their verdant fluorescence begins to appear under normal daylight, and at night under a UV torch, the bright green glow of the nests can be seen up to 65 feet (20 meters), the authors wrote in their report, released Tuesday. (Aug. 24) in the Journal of the Royal Society Interface.
The authors compared the nests of these Vietnamese wasps to those of two others. Polistes species: one from the Amazon rainforest of French Guiana and one from a temperate region of southern France. They found that all of the wasp’s cocoon caps exhibited similar fluorescent properties, although their glow varied both in intensity and in the range of UV light that caused the strongest reaction.
After discovering these mysterious luminous nests, researchers are now wondering if the fluorescence is of any particular use to wasps. On this front, they have several ideas.
It could be that the glowing nests act as beacons for wasps returning to their nests at dusk, or maybe wasps of different species use subtle variations in fluorescence to differentiate the nests of their colonies from those of neighboring colonies. . Or it may be that the fluorescent cocoons protect the wasp larvae from harmful UV rays that would otherwise disrupt the development of the larvae.
Previous studies suggest that the development of wasp larvae is strongly influenced by the relative length of day and night; therefore, the glowing cocoons can help control the amount of daylight that reaches the larvae as they develop into pupae, the authors wrote. “The last hypothesis is my favorite,” Schöllhorn told Live Science.
Vietnamese Polistes species typically breed during the rainy season, between June and August, when cloud cover blocks a significant amount of visible light reach the nests but still allows a fair amount of UV light to pass through. By illuminating the cocoons, this residual UV light can increase the overall light exposure of wasp larvae during development, thereby influencing their growth, the authors wrote in the study.
In future studies, the authors wish to determine the chemical structures of fluorescent compounds in nests. They also plan to see if the compounds could have potential uses in biological research or medicine; for example, fluorescent compounds are often used to label molecules in the body.
Originally posted on Live Science.
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