The brilliant secret that mammals have been hiding | ET REALITY


At first, it seemed to be another quirk of two already unusual animals: Flying squirrels and platypuses were found to fluoresce, absorbing invisible ultraviolet light and re-emitting it in a shocking pink or bright cyan.

But they are by no means alone. According to a document published in the journal Royal Society Open Science This month, lions, polar bears, scaly-tailed opossums, and American pikas also shine. The same goes for all the species of mammals that a group of scientists could get their hands on.

While this large study of museum specimens does not reveal any broad evolutionary benefits, it overturns the view of mammalian fluorescence as an occasional and mysterious quirk. Instead, it appears this trait is “basically the default,” said Kenny Travouillon, curator of mammography at the Western Australian Museum and lead author of the paper.

While scientists have documented fluorescent mammals to more than a century, there has been an increase in interest in the topic in recent years. Researchers illuminating backyards, forests and museum display cases with black lights have come up with a box full of discoveries.

Most of the resulting studies focused on one species, or a few, “trying to better understand the nuances of the trait” in a single type of mammal, he said. Erik Olson, an associate professor of natural resources at Northland College in Ashland, Wisconsin, who helped discover fluorescence in flying squirrels, platypuses and spring hares.

He was not involved in the new study, in which researchers examined museum specimens of 125 species belonging to more than half of the extant mammal families, from Antilocapridae (pronghorns) to Vespertilionidae. (evening bats).

They found some fluorescence in all of them. The survey“It clearly establishes a broad distribution of the trait within mammals,” Dr. Olson said, “something I didn’t expect.”

Dr Travouillon said the idea for this survey came about in 2020 when the discovery of the platypus prompted researchers at the Western Australian Museum to shine an ultraviolet lamp on their own collections. They found turquoise-tinged wombats and bright-sided flying foxes. But did these stuffed specimens really shine? Or could something else be to blame, such as preservatives or fungi?

Together with colleagues at Curtin University in Perth, the team used a spectrophotometer to expose the samples to ultraviolet light and analyze any fluorescence emitted. They also tested newly acquired specimens of several species, including a platypus, a koala and an echidna, before and after conservation.

Preservation with borax and arsenic affected the intensity of fluorescence, increasing it in certain cases and attenuating it in others. But it never created fluorescence where there was none.

This before-and-after test is “a major contribution to understanding the effects of museum preservation on fluorescence,” said Linda Reinhold, a zoologist at James Cook University in Australia, who served as a reviewer on the study.

While performing these tests, the researchers noticed a pattern: Light-colored areas of the fur and skin fluoresced uniformly.

Wondering if this was universal among mammals, they decided to expand their research, drawing on the museum’s collections to includeas many species as possible in the mammalian family tree,” Dr. Travouillon said.

One by one the mammals passed under the spectrophotometer. The light belly and ears of a koala had a greenish fluorescence. The bare wings, ears, and nose blade of a ghost bat were emitting a pale yellow color. Even the white fur of a house cat gave off a faint glow.

Over time, “it started to get a little boring,” Dr. Travouillon said. “We were checking them like, ‘Yeah, it’s glowing.’”

In the end, samples of the 125 species they analyzed showed some degree of fluorescence. In most cases, it came from structures made of unpigmented keratin, such as white fur, the bare skin of pouches and paw pads, or accessories such as quills, claws, and whiskers. A wallaby with albinism, a condition in which production of the pigment melanin is disrupted, glowed a “super intense” blue, Dr. Travouillon said, while the least bright specimen, a dwarf spinner dolphin, fluoresced only in the teeth.

In some cases, the pigmented fur also fluoresces, suggesting that other materials may be involved, as previously observed in spring hares, whose fluorescence does not match their color pattern and has been attributed to pigments called porphyrins.

As in the past, the discovery of UV fluorescent living things raises a complicated question: can mammals detect these glows in nature?

For the most part, the photographs of spotted hares and beaming polar bears in articles like this are taken in artificial conditions that maximize their effect. They do not reflect the appearances of the real world, where the power of the rest of the light spectrum drowns out these hidden colors.

When the team looked for trends, they saw that nocturnal animals had more fluorescence in terms of surface area than diurnal ones, although the difference was small.

Additionally, “prey species tend to have it on their bellies, but carnivores tend to have it on their backs,” Dr. Travouillon said, suggesting a possible moonlight glow effect that could help predators recognize your own species. Other experts, like Reinhold, question whether moonlight would provide enough ultraviolet rays for this to happen.

But it’s hard to imagine any use for some animals newly added to the brightness chart, like the southern marsupial mole, which is blind and spends its life entirely underground, Dr. Travouillon said.

Innes Cuthill, a professor of behavioral ecology at the University of Bristol in England, who was not involved in the paper, said it should put an end to the idea “that fluorescence in animals is necessarily a signal.”

But we may not make it past the end of the rainbow. Given the study’s findings about the potential confounding effects of preservation, examining live animals of these species could be “mind-blowing,” Ms. Reinhold said. “I hope this study inspires others to go into nature with an ultraviolet flashlight (and an appropriate permit, of course).”

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