Biofluorescent fur, first observed in Marsupials, then in Placentals, has now been discovered in the Monotreme Platypus. This means that biofluorescence is all over the mammalian family tree; but researchers are still asking: why?
By Paula Spaeth Anich
The platypus is an ancient mammal with extraordinary talents. It lays eggs, the way the ancestors of all mammals did millions of years ago. It uses mechano-receptors and electro-receptors on its leathery bill to find and capture its prey underwater with its eyes closed, like no other modern mammal. At first glance, the most “normal” mammalian trait of the platypus is its thick coat of brown fur. But as it turns out, the fur of the platypus is remarkable, too.
Researchers recently discovered that the platypus is vividly biofluorescent. As recently published in Mammalia, the animal’s coat of fur which appears evenly brown under visible light (400 – 700 nanometers), appears bluish-green under shorter wavelength ultraviolet light (385 – 395 nanometers). Scientists from Northland College and Colorado State University observed biofluorescence in 3 platypus museum specimens collected in Tasmania and New South Wales during the 19th and 20th centuries. Male and female platypus specimens all displayed the same pattern of vivid biofluorescence across their coats.
Why (some) animals glow in the dark
So what do we know about biofluorescence? When you shine a UV-flashlight or a black light on certain animal species, their bodies absorb those short wavelengths, and emit a longer one — this is biofluorescence. And there are a lot of biofluorescent vertebrates, but very few of them are mammals. Scientists think that biofluorescence in birds, like the bright yellow biofluorescence of the budgerigar, may help individuals attract more mates. Some reef-dwelling fish species are biofluorescent under ambient blue light — their brightly red biofluorescent patches may enable these fish to communicate with one another.
According to the platypus research team, all known mammals with biofluorescent fur are nocturnal. The team is exploring the hypothesis that mammalian biofluorescence may provide a form of camouflage at night. The researchers think biofluorescence might just be one of the many unique things that mammals do to survive and thrive at night.
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