15th July: Duck-billed platypus

On this date in 1922 the duck-billed platypus was first exhibited in the US, at the Bronx Zoo in New York. Everyone knows the platypus is a mammal which lays eggs and lives in Australia - but what else is there to know about these strange creatures?

1. The Latin name for a platypus is Ornithorhynchus anatinus, which literally means "bird snout" in Greek; and anatinus, which means "duck-like" in Latin. The common name, platypus, means "flat-footed". Early British settlers called it "watermole", "duckbill", or "duckmole". Scientists are divided over what the plural of platypus should be. Platypuses? Platypus? Platypi? Platypodes? Take your pick.
2. The platypus is the only living member of its family although fossils suggest it once had relatives. The oldest discovered fossil of the modern platypus dates to about 100,000 years ago, during the Quaternary period.
3. It isn't quite unique in the mammal kingdom for laying eggs. There are four other mammal species which do, and they are the four species of echidna. After mating (June to October) the eggs develop inside the female for 28 days and are incubated for about 10 days after laying. The female platypus builds a special burrow for laying her eggs and raising her young, which can be up to 20m (66 ft) long and blocked at intervals with plugs which presumably keep water and predators out and help regulate the temperature. The male plays no part in caring for the young.
4. The female platypus produces milk, but doesn't have teats. Instead, she secretes milk through her skin. The milk collects in grooves on her abdomen and the young lap it up.
5. The diet of the platypus includes annelid worms, insect larvae, freshwater Shrimp, and freshwater yabby. It either digs its food out of the river bed or catches it while swimming. It stores its food in cheek pouches rather like a hamster does so it can eat it at leisure out of the water. The platypus needs to eat about 20% of its own weight each day. Another unusual feature of the platypus is that it uses electroreception to find food. It can detect the small electrical fields generated by muscle contractions in its prey. The only other mammals which do this are Dolphins and echidna.
6. An adult platypus has no teeth. It grinds up its food with heavily keratinised pads in its jaw. The young have three teeth but lose them before leaving the burrow.
7. Male platypuses are venomous, another rare trait among mammals. They have a spur on their hind foot which releases a nasty venom which contains defensin-like proteins (DLPs), three of which are unique to the platypus. While the venom isn't deadly to humans it will cause severe pain, oedema and a hypersensitivity to pain which can last for months afterwards.
8. Captain John Hunter, the second Governor of New South Wales, was one of the first Europeans to see a platypus in around 1788. He skinned one and sent the pelt back along with drawings of the animal. The scientists at home thought he was having a laugh. They thought a taxidermist had sewn a duck's beak onto the body of a beaver-like animal. One scientist even took a pair of scissors to the dried skin to check for stitches.
9. The weirdness of the platypus extends to chromosome level. Most mammals have two chromosomes which determine sex - X and Y. The platypus has ten, so a male platypus is XYXYXYXYXY.
10. The platypus is the animal emblem of the state of New South Wales. Famous platypus mascots include Syd, one of the three mascots chosen of the Sydney 2000 Olympic Games along with an echidna and a kookaburra; Expo Oz, the mascot for World Expo 88 in Brisbane; and Hexley, the mascot for Apple Computer's BSD-based Darwin operating system, Mac OS X.