OSB archive
OSB archive

Platypus: a genomic cocktail

Pete Wilton

Is a platypus five times sexier than a human? Well chromosomally-speaking it is: it has ten chromosomes that determine sex to our two. This is just one of the findings from a report in today's Nature.

Work by Chris Ponting from Oxford's MRC Functional Genomics Unit and colleagues has revealed that just as, to look at, the platypus is a pick 'n' mix of different animal attributes so its genome resembles an astonishing DNA cocktail: take sex chromosomes from birds, milk-production chromosomes from mammals, mix with reptilian chromsomes for a venomous bite, shake well and then add a twist unique to monotremes.

Of course, in a sense, it's not surprising that a creature that looks like a cryptozoologist's daydream has such a patchwork of genes. What is remarkable is just how different they are from mammal genes and how similar they are to those of other animal families - for instance proteins from platypus venom are the same as proteins in reptile venom even though the two evolved independently.

And then there's the twist: The platypus bill may look familiar and duck-like but it conceals a unique sensor system that enables this accomplished hunter to use electricity to detect its prey in the silty underwater gloom.

All of this might suggest that the platypus is some sort of zoological joke were it not for the fact that we share a common mammalian ancestor with them that lived around 170 million years ago. As Chris says this gives it a particular importance as a 'missing link' between the reptile-like, egg-laying mammals of the ancient past and the milk-rearing mammals we're all familiar with.

So, for all its idiosyncracies, maybe it's about time we celebrated the platypus as 'one of us'.

Watch a Nature video explaining the project, featuring Chris Ponting, here