What comes to mind when you think of a platypus? A secret agent in an animated show? A rare Pokémon? Or maybe you've been lucky enough to see the real thing in action! (I'm totally jealous if you have.)
If you're like me, you might think that the most unusual traits of the platypus are the bill and its egg-laying ability. That is until I dug a little deeper to find out just how strange this little creature really is. 😱
Here are a few facts that surprised me the most:
"Platypus" means "flat foot." (It's Greek, by the way, so the proper plural version would be platypuses or platypode 😁) Have you ever seen their feet up close? The front feet have much broader webbing than the back. The platypus will primarily use the front legs to paddle under water - the back legs and tail help steer. Those same feet will curl up on land as the platypus walks on its knuckles!
Speaking of feet, stay away from the venom-ejecting barb on the back legs of the mature males. In a rare example of mammals producing venom, rival platypuses will battle it out with their barbs when competing for a mate. If a person is unlucky enough to get stung by the barb, they will experience excruciating pain that could last up to months.
The platypus excretes waste and lays eggs through one opening called the cloaca, much like a bird or frog. Once the babies hatch, the mother platypus will produce milk for its young. The babies don't nurse like your typical mammal. Instead, the mother "sweats" milk through pores in her skin that pool on the surface of her belly. Weird!
Here's my favorite secret platypus ability: it can detect electrical signals through its bill. When little critters, like worms, move around in cloudy river water, the platypus can detect the electrical activity caused by the prey contracting their muscles. This helps the platypus swoop in for its lunch with deadly accuracy (did I mention that the platypus loses its teeth as it grows into an adult?!).
What you can't see about this animal is just as weird as what you can see. Scientists are studying platypus DNA, and the results are just as odd as you might expect.
The lone species of platypus and four species of echidna (another odd animal) are the only monotremes, an order of mammals who lay eggs. Monotremes share about 80% of their genome with common mammals, but the rest of their DNA is a better match to reptiles, amphibians, and birds. Here's an example: the genes that control the position of the limbs of the platypus, which go "out" instead of "down", are more similar to reptiles than mammals.
In terms of reproduction, female mammals inherit XX chromosomes from their parents and males inherit XY chromosomes. For the platypus, there are five different versions of both the X and Y chromosomes. If that's not confusing enough, the genes on some of these chromosomes produce proteins found more commonly in bird reproduction. The proteins create sexual dimorphism like we see in many birds, where male and female versions of the organisms have different traits.
One of the ways that the male and female platypus differ is in their overall size. Take a look at the graph below to see how their average body masses stack up.
If I brought this graph to my classroom, here are a few questions I'd have to go along with it:
💡The lines in the middle of the red and blue boxes represent the mean masses of male and female platypuses. What is the difference between the mean masses of the males and females?
💡Look at the boundaries of the red and blue boxes. These show a typical range where the platypus mass could fall. What is the mass range for the male platypus? What is the mass range for the female platypus? Which sex has a greater range?
💡The ratio of average male platypus mass to female platypus mass is 1.60 : 1. If a male has a mass of 2 kg, what would be the corresponding mass of a female? Use the ratio to calculate your answer.