By John Upton
It’s a mammal that lays eggs. It’s one of the few mammals in the world equipped with venomous barbs, which are found on the males’ rear legs. The feet of those legs are shaped like otters’, yet the bills are duck-shaped and the tails resemble beavers. It has no visible ears and its sex chromosomes more closely resemble those of a bird than those of virtually any other type of mammal.
And today we’re going to shower you with some wonderful news: In the rivers of eastern Australia, where the species is native, the ecological freak show known as the platypus is doing awesome.
These little guys are elusive; they can be impossibly tough to spot as they get about their semi-aquatic lives. But get about their semi-aquatic lives they do, even as great cities pop up around them, diving frequently for worms, yabbies and other prey, and laying thumbnail-sized eggs in nests on vegetated riverbanks.
Sure, there are probably substantially fewer platypuses today than there were hundreds of years ago, before Britain started using the sparsely populated continent as a jail, paving the way for widespread urbanization. The critters have pretty much disappeared from the mighty Murray River, for example. But in a country where wildlife populations have been wrecked by invasive species, water diversions and salinity woes, this primitive beast is a freakin’ soldier.
The greatest unnatural threats to the platypus comes from freshwater diversions, declining water quality, the loss of vegetation along waterways and the popular past-time of yabbying. Baited traps are thrown into rivers and hauled back out full of yabbies, which are a ubiquitous freshwater crayfish in Australia. Unless a trap is specially modified, any platypus that darts into it to grab a yabby runs the risk of drowning.
Despite those threats, and with a little help from conservationists, the platypus faces no looming threat of extinction. It’s not considered endangered or threatened. It continues to do awesome.
It should perhaps be unsurprising that the species is thriving: It has been doing so for hundreds of millions of years.
To help understand the genetic history of our own sexuality, researchers studied platypus genes. Humans and most modern mammals have two sex chromosomes, with the arrangement of X and Y chromosomes determining gender. But the researchers discovered that the complex sex chromosome arrangements of platypus are more similar to birds than they are to us.
“Platypus sex chromosomes have strong homology with bird, but not to therian (marsupial and placental mammal) sex chromosomes,” the researchers wrote in a 2008 paper in Genome Research. That led the scientists to conclude that our modern sex chromosomes evolved after egg-laying mammals, known as monotremes, split away from the other mammalian varieties as evolution took its course some 170 million years ago.
So not only are these monotreme mammals outwardly unusual, they are extremely genetically unique. Along with egg-laying echidnas, the platypus is a mammal that is far more primitive than even the pouch-bearing marsupials that dominate the Australian lanscape. And when it comes to sex, they resemble egg-laying birds, not gestating humans.
Which we think is pretty awesome.
Peer inside a platypus nest: