The Platypus Paradox
Australia’s long geographic isolation and tectonic stability have enabled the development of unique fauna. At some point, evolution on the land down under chose a different path and plenty of Australia’s animal kingdom is not seen anywhere else. Many ecological niches that are elsewhere occupied by placental mammals are filled by marsupials. It is the only continent on which you are more likely to encounter a venomous snake than a non-venomous one. Australia is home to a variety of distinct invertebrates - insects, arachnids and molluscs that fill many important ecological roles such as decomposers, pollinators, and food sources.
When I think about Australia, there is one specific species that pops into my mind - the Platypus. Mother nature must have found a new source of inspiration and creativity when it was working on the eastern part of Australia; The result is a mole-like animal that has a bill of a duck, a tail of a beaver and its inner parts resemble those of a reptile. It lays eggs and yet it suckles mother’s milk. It has the ability to sense electrical currents. Oh, and if that is not enough, it is venomous. The Platypus displays such an amalgamation of properties, when the first platypus specimen arrived in Europe and scientists laid their eyes on it, they believed that it was a hoax.
In 1798, the first platypus specimen has landed in Europe, preserved in spirits, to be examined by naturalists and scientists. As nothing like this was known before, many of the scientists had doubts that this is a real organism at all. It was easier to believe that it was the creation of an inventive taxidermist. George Shaw, an English botanist and zoologist, was the first to write a description of the little animal. He has confessed that he could not believe what he saw. A bill of a duck on a quadruped was unheard of. It took a careful examination for him to conclude that the animal he examined was not a fake.
Shaw proceeded to name this newly discovered organism; he gave it the binomial name of Platypus anatinus - a name that means flat-foot duck-like. At about the same time, Johann Blumenbach, a German naturalist, had named it Ornithorhynchus paradoxus; the genus name means bird-snout and the species name was chosen to reflect the paradoxical shape of the platypus. And so, for a while, the platypus went by two names. When it was discovered that the name Platypus was already taken by a genus of beetle, a combination of the names was decided upon - Ornithorhynchus anatinus, that is bird-snout duck-like. The name Platypus has stuck as the common name of this curious creature.
The platypus, a small, amphibious, mostly nocturnal burrow-dweller is the only extant species in its genus. Its closest relative is the echidna, of which three types exist (four, if you wish to include Knuckles). Together, they form the order Monotremata, which is one of three groups of living mammals; The others being placentals and marsupials - both are much larger groups than the monotremes. What separates the monotremes from the other groups of mammals is the fact that these species lay eggs, instead of giving birth to live young.
The assortment of characteristics displayed by the platypus has drawn a lot of interest and confusion. Children’s stories used to tell that the platypus, for being a mixture of other animals, was not allowed to enter Noah’s ark. The scientific world was split in the case of the platypus for most of the 19th century. For a long time it was not known if the platypus lays eggs or if it produces milk. It has taken quite a while to decide whether to classify the platypus as a bird, a reptile or a mammal. Let’s examine a few of the platypus more interesting traits for ourselves.
The platypus is a small, furry animal. The male platypus is slightly bigger than the female, at about the size of a house cat. The greater part of its face is covered with its large distinguishing bill, along with two beady eyes that make it look somewhat harmless. It has four webbed paws and a large beaver-like tail. Its brown fur is thick and dense, and it traps air that provides an insulating layer to keep it warm (sounds familiar?). The platypus spends most of its waking hours swimming and foraging for food in cold water. It sometimes rests fully submerged for a few minutes at a time, so the waterproof fur is advantageous. Despite its innocuous appearance, the platypus is carnivorous, and feeds mostly on shrimps and worms, and sometimes on frogs and fish.
The platypus is a Mammal. Possibly the defining characteristic of mammals is, of course, having mammary glands. These are the milk-producing organs, used for feeding the young offspring. These usually come along with nipples that allow for effortless nursing of the young sucklings. Well, the platypus does not have nipples, a fact that acted as another cause for arguments when early attempts to classify the platypus took place. When examined, glands that resemble mammary glands were discovered, but many thought that they were lubricating glands, similar to those found in salamanders. Eventually, it was discovered that these were mammary glands and that milk secretes through the platypus skin. This milk is pooled on the platypus abdomen and so the young can suckle, unlike any other mammal.
The platypuses live in burrows that they dig in the banks of rivers and streams. There are two types of burrows, that serve two roles. The simple-and-small type of burrows is used all year long by both sexes of the platypus. These don’t go very deep, and provide a resting place for the platypuses. They usually live alone, but nests that held a small group of these critters were witnessed in the past. The more-complex burrows are used by females during breeding season. These burrows stretch longer - they sometimes get to 15-18 meters in length. In the deepest part of this tunnel is a chamber that is lined with leaves and dry grass. This is where the platypus mother lays its eggs, incubates them and nurse its babies. These burrows are built to have a few tight passages that are assumed to squeeze the water out of the mother’s fur after she has gone out to forage for food. This helps in keeping the burrow dry and warm for the baby platypuses.
The platypus is the sole mammal to possess a bill. The bill of the platypus does not play the same role as that of a bird or a reptile. When scientists started to study the platypus, they quickly noticed that the mouth and the bill of the platypus were not one and the same. The bill of the platypus serves as its main sensory organ. When it dives, the platypus closes its eyes, ears, and nostrils and so it relies on its bill for sensing its environment and finding the worms and shrimp it digs from the ground to eat. It is assumed that the bill is mostly relied upon on land, as well. The placement of the platypus’ eyes, which give it its timid demeanor, does not suggest a great vision of objects that are in front of the platypus.
The bill is a sensory organ in more ways than one. In addition to mechanoreceptors (normal sensory nerves for gathering tactile information) the front of the bill is also lined with electroreceptors. These are sensory organs that sense electrical currents. That means that other than touching things with its bill, it can also sense physiological electrical currents emitted by its prey. With this sixth sense, the platypus can sense its food even if it is buried or hidden. The bill is where the concentration of these two types of sensors is highest, in a way that resembles the high concentration of sensory nerves on the palm of our hands.
Researchers have noticed that when the platypus swims submerged, it will motion its head from side to side, most likely trying to sense an electrical signal that might mean food. Sometimes, it will wedge itself under something solid and use it as a rest. Then, it will wait motionless up to a few minutes, until it senses anything of interest. Once it has picked up on something, the platypus will use its bill to dig up its prey and swim back to the surface to breathe and eat.
The platypus does not chew its food in the traditional way. Most mammals possess teeth.There are only two mammalian groups that do not - Pangolins and Anteaters. The platypus does grow teeth as a baby, but it will lose them at some point before leaving the burrow for the first time. When the platypus digs up food with its bill, it will also collect some gravel that will use for grinding the food, filling in the role of the absent teeth.
Mammals that produce venom are not unheard of, but they are definitely not the norm. Hence, the platypus is one of the few venomous mammals. It has a spur on its hind feet that delivers a venom that is not lethal but can lower blood pressure, cause severe pain and increase blood flow in humans. Both male and female platypuses have these spurs, but only the males produce venom, and only during mating season. As a result, it is believed that the venom is used as a weapon to control territories and assert dominance between platypuses.
The platypus, portrayed on the back of the Australian twenty-cent coin, has webbed paws and a large, flat tail. These are used for swimming. Contrary to what might seem logical, the platypus uses only its front paws to propel itself through the water, while the hind legs and tail are used for steering. When it is on land, it retracts its webbing and walks on its knuckles to protect the webbing. When it does that, its sharp claws are clearly visible. These claws also may be used as defensive tools.
The platypuses live near many bodies of fresh and brackish water in eastern Australia and Tasmania. Even though their numbers decreased due to hunting, they are not considered endangered. The platypus is a conserved species and it is protected in Australia. Today, their habitats are dwindling though, due to anthropological (humankind related) factors such as dams or pollution that affect the quality of their habitats.
Research on the platypus goes further on even today. With today’s DNA sequencing technologies, genetic testing of the platypus allows us to look at it from new angles. For example, recent studies have found that the platypus is gifted with vomeronasal receptor genes, a type of nasal taste buds. This suggests that the platypus might have a developed ability to smell underwater. This might prove to be a sense that the platypuses heavily rely upon.
We have started studying the peculiar platypus over 200 years ago. For a long while, it has caused a fair amount of confusion. Today, we know enough to classify it but we have a lot to study and learn about it yet. Who knows what other surprising properties this little creature might still hide from us? While scientists are busy studying these antipodean mammals, the platypus, in a manner that reminds me of the hobbits of the shire, keeps floating lazily on the water, unaware of the passage of time and the troubles of the world around them.
As always, if you want to read some more - about Winston Churchill's platypus, what is a Platypusary or the (clickbait warning) Giant Platypus (it's a lie), then you should check out the Additional Notes to this article.
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Thanks for reading!
D. S. Cyprus.