After mating, a female echidna lays a single, soft-shelled, leathery egg, about the size of a dime, into her pouch. Ten days later, the baby echidna called a puggle and smaller than a jelly bean hatches.
Echidnas are mammals without nipples. Like all mammals, echidnas feed their young milk. But they do it without nipples. Instead, female echidnas have special glands in their pouches called milk patches that secrete milk, which the puggle laps up. They are electroreceptive. Like the platypus, the echidna has an electroreceptive system. While the platypus has 40, electroreceptors on its bill, echidnas have only , electroreceptors on their snouts. They're toothless but make up for it with their tongues.
At the end of their slender snouts, echidnas have tiny mouths and toothless jaws. They use their long, sticky tongues to feed on ants, termites, worms, and insect larvae.
Since they have no teeth, echidnas break their food down with hard pads located on the roof of the mouth and back of the tongue. Watch a video of an echidna hunting here.
Part of this might be due to their enlarged neocortex, which makes up half of the echidna's brain compare this to about 30 percent in most other mammals and 80 percent in humans. It was long thought that echidnas didn't enter rapid eye movement REM sleep at all, the type of sleep associated with dreaming in humans.
But recently researchers found echidnas will experience REM sleep if they're at the right temperature. They host the world's largest flea.
Retrieved June Cason, M. Animal Diversity Web. Dell'Amore, C. These new findings help to recast these archaic features in a positive light—for instance, whereas the reptilelike shoulders are poor for running fast, they provide strong bracing, allowing for huge shoulder and arm musculature to help echidnas dig into the dirt and platypuses maneuver in the water.
Note: This article was originally printed with the title, "Extreme Monotremes. Already a subscriber? Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science.
Get smart. Sign up for our email newsletter. The mystery then is why any monotremes survived. Now Phillips and his colleagues suggest that platypuses and echidnas lived on because their ancestors sought refuge where marsupials could not follow — the water. Platypuses are amphibious creatures, while echidnas — the anteaters — are terrestrial. However, new genetic evidence and comparisons with fossil monotremes suggests that echidnas only diverged from platypuses 19 to 48 million years ago.
This means echidnas recently had semi-aquatic predecessors and only later recolonized the land. A number of aspects of echidna biology are consistent with an amphibious platypus-like ancestor — a streamlined body, rearward-jutting hind limbs that could act as rudders, and the contours of a duck-like bill during embryonic development. It was thought that the much shorter fossil record for echidnas, from about 13 million years ago, was just due to the patchy nature of the fossil record," Phillips said.
Their new findings suggest "the lack of early echidna fossils was in fact because they simply had not evolved yet. The researchers conjecture that marsupials could not afford a substantial invasion of aquatic environments because when they are born, they need to suckle milk constantly for weeks; newborn marsupials could drown if their mothers ever had to venture into the water.
Not only that, but paper suggests that the change from a platypus-like body form to an echidna-like body form appears to have happened surprisingly quickly, in less than 15 to 25 million years. That such a major change in overall morphology could happen so quickly is intriguing.
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