This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
After nearly two months of wandering the Southern Hemisphere and a few weeks of recovery post-return, it's time to get back into the blogging here at the Artful Amoeba. We'll begin with a few wrap-up posts of stuff I didn't get time to blog about while I was down under before resuming our regularly scheduled program.
For your Saturday morning enjoyment, here is an adorable echidna I filmed while visiting Cleland Wildlife Park in South Australia.
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It appears to be a spiny potato sprouting a brown parsnip. It's a monotreme, a lineage that split off from the group that would give rise to both marsupials and mammals. You may know monotremes better by their other famous member: the duck-billed platypus.
This one was up and about the day I visited and having a nice bit of a trundle-about before it snuggled in for a snooze. Look carefully at its style of walking and particularly at its hind feet. It appears that the claws on its hind feet point backwards as it walks.
Monotremes include just the duck-billed platypuses and four species of echidna. The echidnas specialize -- like the totally unrelated mammalian anteaters -- in digging and eating ants, termites, grubs, or worms, depending on the species. They have no teeth, but have what one must imagine to be a truly prodigious and lethal tongue.
Like the platypuses, echidnas have a strange mix of reptilian, mammalian, and marsupial characteristics that would support the hypothesis that they branched off from the common ancestors of mammals and marsupials before those two groups split. They lay eggs, which they immediately deposit in a pouch where their young hatch. (That's right! Echidnas are hatched!)
The females have a single opening for their digestive, reproductive, and urinary tracts called a cloaca, just as most reptiles do. If you perform a self-inspection, you will find this is not the case for you, and, interestingly, if you are a mammal, your situation vis a vis these conduits will also vary based on your gender.
They also secrete milk, but not from a proper nipple -- merely from a patch of pores. And they also have some freaky-deaky electrosensors on their snouts. No idea what that's about, although if you, the reader do, please feel free to fill me in.
And then there's the bizarre echidna penis. It has *four* heads, of which two are only used at any given time, and which alternate with the other two in sequential bouts of echidna baby-making. The female reproductive tract forks, hence the need for a double-barrel. But a quadruple, alternating barrel? I'm not sure how this evolved, but I think I can safely say it is a design that would make the boys at Craftsman proud.
