The platypus is even weirder than you thought

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Biofluorescence, in which short wavelengths of light are absorbed and longer wavelengths are re-emitted by living organisms, has been observed in a wide range of fishes (Sparks et al. 2014), reptiles and amphibians (Gruber and Sparks 2015; Lamb and Davis 2020) and birds (Pearn et al. 2001; Weidensaul et al. 2011). Within mammals, biofluorescence of the pelage under ultraviolet (UV) light has been previously documented in nocturnal–crepuscular New World taxa including marsupial opossums (Meisner 1983; Pine et al. 1985) and placental flying squirrels (Kohler et al. 2019). Here we document the discovery of fluorescence of the pelage of the platypus (Ornithorhynchus anatinus)—to our knowledge, the first report of biofluorescence in a monotreme mammal under UV light.

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