The Platypus – Did You Know?

In my new Did You Know blog series, learn 10 facts about one animal in 5 minutes. In the series, I’ll tell you stuff you didn’t already know (hopefully). Let me know how many surprised you!

Today I’m going to blow your mind about an ancient mammal: the duck-billed platypus.

Did You Know that platypuses…

1. …Are one of only five mammal species that lay eggs instead of giving birth to live young (Monotremes). The other four are species of echidna. The eggs develop internally for 28 days and are incubated externally for 10 days. The platypus genome has both reptilian and mammalian genes associated with egg fertilisation.

2. …Are one of very few venomous mammals. The male has a spur on the hind leg that can cause severe pain in humans.

3. …Is a recognisable and iconic symbol of Australia. It is endemic to eastern Australia, including Tasmania, and appears on the reverse side of the Australian 20-cent coin.

4. …Completely stunned European naturalists when it was first discovered in 1798. The specimen of a bizarre duck-billed, beaver-tailed, egg-laying mammal was first thought a hoax.

5. …Is the only type of mammal (except some dolphins) to use electroreception. Monotremes (platypuses and the four echidna species) can locate their crustacean prey by sensing the electric fields caused by their muscle movements. A sheet of electroreceptors is found on the bill. By shaking its head from side-to-side while swimming it can detect differences in signal strength to sense the direction of the electrical source.

800px-Platypus-sketch
The platypus (Ornithorhynchus anatinus) is one of the world’s most primitive mammals. John Gould print image: Wikipedia Commons.

6. …Closes its eyes, ears and nose when it hunts underwater. Solely relying on electroreception and sense of touch (mechanoreceptors) on the bill, prey are found by detecting both the electrical fields and mechanical pressure pulses they emit. The different arrival times of these two signals to the bill signify the distance to the prey.

7. …Have unusual eyes among mammals. Their poor vision is more similar to Pacific hagfish than to other tetrapods (vertebrates higher than fishes) and the eyes contain double cones involved in luminance (brightness) perception, which most mammals do not have. Although vision may have been important for hunting in distant ancestors, this may have been sacrificed for the electrosensory system that is better suited to an aquatic and nocturnal lifestyle.

8. …Have a unique swimming motion among mammals. Webbed feet propel them through the water, although only the front feet are used for power in an alternate rowing motion; the hind feet and tail are used for steering.

9. …Feed their young with milk released through pores in the skin. Although platypuses have mammary glands – one of the defining features of a mammal – they lack teats. Instead the blind, helpless and naked young drink milk that pools in grooves on the mother’s abdomen.

10. …Are descended from the extinct monotreme Steropodon.  The fossilised specimen is thought to be about 110 million years old, making it the oldest mammal fossil to be found in Australia. Another fossil relative, Monotrematum sudamericanum, can be placed in the supercontinent Gondwana (when Antarctica joined Australia and South America) up to about 167 million years ago.

Feel free to make suggestions about other animals you want to see featured in the series!

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