Figure 1: Perry the Platypus, a Disney character from the show Phineas and Ferb
Recent articles from National Geographic and Science News have brought to light an interesting discovery. It was found that the fur of platypuses exhibited biofluorescence. This was not expected from researchers because very few other mammals, such as a few species of flying squirrel and a few marsupials such as opossums, are known to be fluorescent. Fluorescence works when the fur absorbs a photon at one wavelength and emits a photon at another wavelength with common emitted colors being red, green, orange, and blue. When the platypus pelt was illuminated by ultraviolet (UV) light the pelt emitted a blue-green glow similar to the color of Perry the Platypus. However, due to the UV light saturating everything with a purple hue, a yellow filter was used to produce a more “true” color to what the eye sees.
Figure 2: This picture shows what platypuses look like when illuminated with normal visible light and UV light with and without the yellow filter, and the UV reflectance.
The purpose of the biofluorescence is still unknown to researchers. Platypuses are already
one of the strangest creatures alive on several counts. Not only are they one of only two
mammals that lay eggs, but they also have poisonous spines on their rear legs and have the
ability to sense electrical signals in water to aid in catching prey. There are several theories about
why platypus fur fluoresces ranging from camouflage to a simple vestigial trait. The basis of the
camouflage theory is that common predators of platypuses such as birds of prey, dingoes,
crocodiles, and Murray Cod can see in the UV, and since the platypus absorbs UV light it gains
camouflage. On the other hand, it could have no real function and just be an ancestral trait that
was retained and has no practical use anymore. This is plausible because fluorescent fur has beenfound in all 3 major branches of mammals: monotremes (platypuses), marsupials (opossums),
and placental mammals (flying squirrel). While there are still more theories such as aiding in
intraspecies communication, only one real correlation that has been found, the dark. All the
known cases of mammals being fluorescent occur in mammals that are active at night or in the
low light time such as dusk or dawn. Since there is less known about the nocturnal world, there is
a high probability that there are lots of other mammals that exhibit biofluorescence. As research
continues more information on the actual cause and reason for the biofluorescence will come to
light.
Extra Chemical Speculation: It is known that the species of fly squirrels fluoresce pink and platypuses fluoresce blue-green. Therefore, the chemical source of the biofluorescence is most likely different for each animal. None of the articles specified any compounds responsible for the biofluorescence, but typical organic compounds that fluoresce strongly are aromatic and/or heterocyclic compounds. It is likely that the source of biofluorescence in mammals is an unknown aromatic and/or heterocyclic compound.
Sources:
● https://www.nationalgeographic.com/animals/2020/11/glowing-platypus/#close
● https://www.sciencenews.org/article/platypus-glow-blue-green-ultraviolet-light-fluorescent-fur
Clever title. This is one of those things that is interesting because it is unexpected. It doesn't seem to have profound consequences, but it is certainly interesting and appropriate. The graphics are captivating. Your summary of the articles is clear and engaging. I like your speculation about the identity of the fluorescent molecule. It is worth pointing out the molecular roots of all biological phenomena.
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