Platypuses just got even weirder

Embargoed until: Publicly released: 2026-03-18 11:01

Australia; International

AusSMC

Platypuses lay eggs and have a bill like a duck, but it turns out that these weird characteristics are not the only things they have in common with birds. Researchers have found that platypus hair contains an unusual hollow version of a structure, called a melanosome, which contains colour pigments - something previously only found in birds. In birds, hollow melanosomes give feathers their iridescence - but in platypuses, they seem only to produce brown colours. The team hasn't found these structures in echidnas or any other mammals they have studied so far, making the platypus even more unique. The researchers say that for over 200 years after platypuses were first described as something in between birds and mammals, they have found another example of similar characteristics evolving independently in birds and platypuses.

News release

From: The Royal Society

A unique hollow melanosome morphology in the hairs of the platypus Ornithorhynchus anatinus
Melanin pigments are responsible for the colours of many animals. In vertebrates, they are housed in tiny structures called melanosomes, which usually range from spherical to rod-shaped. For decades it was thought that hollow melanosomes occurred only in birds and are always linked to angle dependent colouration. Here, we present hollow, spherical melanosomes in the hair of the platypus. These structures are absent from other monotremes, and all other mammals studied to date. Remarkably, they only produce brown colouration, not functioning in creating iridescence. This finding opens new questions about how melanosomes evolve and function in mammals.

Gotta catch 'em all - Platypuses, the egg-laying mammals with duck bills and beaver tails, can add a new curious trait to their list. Researchers have found evidence of hollow melanosomes, previously thought to be exclusive to birds, in the animal. Melanosomes determine the colours of many animals, and in birds their hollowness is linked to iridescence. This doesn’t seem to be the case in platypuses, opening new questions about the evolution and function of the organelle.

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Journal/
conference: Biology Letters

Research:Paper

Organisation/s: Ghent University, Belgium

Funder: This work was supported by the Air Force Office of Scientific Research (grant numbers FA9550-1-18-0447 and FA9550-1-23-0622); the European Office of Aerospace Research and Development (grant number FA8655-2-23-0622); the Research Foundation Flanders (FWO) (grant number G0E8322N); the Ghent University Special Research Fund (grant number PDO.2023.0006.01); the Human Frontier Science Program (grant number RGP0047); and Horizon Europe (grant number 101151258).

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