Photo: Figure 1 from “Biofluorescence in the platypus,” Mammalia, 15 Oct 2020

This Sunday’s #sciku is about the recent accidental discovery that platypuses have fluorescent fur, joining a surprisingly wide phylogenetic range of mammals to feature the trait. Opossums, flying squirrels, and platypuses diverged from each other over 20 million years ago, and yet they all glow in UV light. What’s interesting is that we had no idea they were fluorescent, and still don’t know why it’s adaptive. It seems to be a feature of nocturnal mammals, so likely involves either intra-species signaling—perhaps a sexual fitness display?—or a kind of camouflage to hide from UV-sensitive predators. None of the articles make much of it, but notice in the photo how the coloring is completely different on the dorsal (back) side compared to the ventral (stomach) side. That reminds me of the coloring patterns on sharks and military aircraft, that camouflage themselves differently for those looking from below than those above. Flying squirrels are the same, only glowing on their bellies. Makes me think it’s more about hunting than being hunted. Platypuses eat things like shellfish and aquatic worms, which also bioluminesce. My hunch is that they’re fooling their food.

Anyway, we only discovered glowing squirrels a few years ago, and platypuses this week! So much of nature leaves us in the dark.

fluorescent fur!
the neighbors throw a party
without us