The Mystery of The Platypus Deepens With The Discovery of Its Biofluorescent Fur

 Scientists are seeing the Australian platypus in a whole new light. Under a source of illumination, this bizarre-looking creature appears even more peculiar than normal, glowing a soft, greenish-blue hue rather than the everyday brown we're wont to see.

The recent discovery has not been found in the other monotreme species, and it's scientists wondering: Have we been overlooking an ancient world of fluorescent fur?

"Biofluorescence has now been observed in placental New World flying squirrels, marsupial New World opossums, and therefore the monotreme platypus of Australia and Tasmania," the authors write.

"These taxa, inhabiting three continents and a various array of ecosystems, represent the main lineages of Mammalia."

(Anich et al., Mammalia, 2020)

Over the centuries, bio fluorescence has been reported in various plants, fungi, fruits, flowers, insects, and birds. It's only recently, however, that scientists have begun to actively hunt examples within the kingdom. Many discoveries thus far were simply happenstance. 

In 2015, for example, scientists chanced upon the primary fluorescent marine turtle while searching for glowing coral. Two years later, the primary fluorescent frog was found unexpectedly, and therefore the team advised others to "start carrying a UV flashlight to the field".

Among mammals, the primary example of bio fluorescence was reported in 1983 within the Virginia opossum, the sole marsupial in North America. But it wasn't until 2017, and by complete accident, that researchers uncovered something similar in North America's flying squirrels (Glaucomys), which are categorized as placental mammals.

While conducting an evening survey of lichens, researchers were amazed to show their LED torch on a bright, bubble-gum pink opossum.

One of the sole things the opossum and squirrel share in common is their nocturnal lifestyles. this is often also when UV light is at its strongest, which suggests the trait can be common among mammals most active in the dark, dawn, or dusk.

Like flying squirrels and opossums in North America, platypuses in Australia are active in the dark. However, they're separated from these other animals by some 150 million years of evolution.

Australia's hidden glows

Despite being home to a number of the foremost primitive mammals on Earth, relatively little attention has been paid to bio fluorescence in Australia's animals. But if they even have glowing fur, the trait may well be way more ancient and potentially more common among mammals than we thought.

"It was a combination of serendipity and curiosity that led us to shine a UV light on the platypuses at the sector Museum," recalls biologist Paula Spaeth Anich from Northland College. 

"But we were also curious about seeing how deep within the mammalian tree the trait of bio fluorescent fur went."

Researchers began with two stuffed museum specimens, a male and a female collected in Tasmania. These creatures' fur was found to soak up short UV wavelengths so emit actinic radiation, fluorescing green or cyan. 

Examining another platypus specimen collected from New South Wales, researchers found the identical thing.

"The pelage of this specimen, which was uniformly brown under actinic radiation, also bio fluoresced green under UV light," the authors write.

To their knowledge, the team says this can be the primary time bio fluorescence has been reported in monotremes. However, in June of this year, a member of The Queensland Mycological Society claimed to own discovered a road-killed platypus with an analogous glow.

"The fur of the platypus mostly appeared dark/purple needless to say under the UV light, but a number of it turned mosstone, although not brightly so," writes Linda Reinhold within the society's non-peer-reviewed newsletter.

Reinhold also found two northern brown bandicoots on the road with fluorescent pink fur, and he or she did manage to snap those.

Lighting up the dark

It's still too early to mention what advantage this trait might give nocturnal mammals – our sample sizes are too small – although scientists have some ideas.

In 2017, when the flying squirrels were discovered with bio fluorescent fur, some thought it would need to do with camouflage since many trees are covered in bio fluorescent moss and lichen.

However, the bandicoots found by Reinhold are ground-dwelling mammals, and their fluorescence may make them stand out.

Standing out may well be a plus, betting on the circumstances. for a few birds, their bio fluorescent feathers play part in mating rituals. Fish use the trait to speak among themselves.

Yet within the platypus, both the male and feminine specimens showed similar fluorescence, suggesting the trait isn't sexually dimorphic. What's more, because the platypus usually swims with its eyes closed, the glow in its fur probably isn't there to speak with others of its kind.

Instead, researchers think it'd help camouflage the platypus from other UV-sensitive nocturnal predators by absorbing UV light rather than reflecting it.

Further study is required within the wild before we are able to say of course what's happening. we do not even know the way the bio fluorescence of this fur even works, and also the benefits of this trait might vary from species to species.

Still, the very fact that this strange glow exists across the fur of egg-laying monotremes, marsupials, and placental mammals suggests it's deep roots.

If nothing else, the invention could be a nice reminder of our sheer ignorance.