The Platypus

The Biological characteristics of the Platypus

The Platypus - Ornithorynchus anatinus. A truly unique animal.

The most notable of physical adaptations is the platypus’s bill. The bill is used as a tool for, both, locating and mechanically digesting food. Touch and electroreceptors on the bill enable the Platypus to navigate the river without the use of its eyes or ears. The touch sensitive pores operate via a pushrod device which triggers nerves below the surface, while the electrosensative pores contain a mucus gland attached to nervous fibres, able to detect the minute electrical impulses generated by the muscle activity of prey, as well as the small electrical field created as water flows over stationary objects.

A behavioural adaptation of the Platypus is that it sweeps its bill underwater from side to side 2-3 times a second, sifting its way through the river bed and picking up the electrical impulses.

Another physical adaptation of the Platypus is its shoulder girdle. The forefoot muscles are reinforced by an interclavicle, which aids the platypus in digging its burrows.  The acute eyes and ears, necessary for a nocturnal lifestyle, are closed tight within furrows when the platypus submerges. In no way does it use sight or sound in foraging underwater. Furthermore, the platypus’ eyes and nostrils are situated on top of its body, an adaptation to aquatic lifestyle, allowing it to stay largely submerged while still able to breath (see above) – similar to the hippopotamus and crocodile.

The streamlined shape of a platypus assists in moving through water without much resistance.

A platypus’ coat consists of two layers. The underlayer consists of fine hairs which trap air –acting as an insulator- to keep the monotreme warm. The outer layer acts as a water seal, waterproofing the platypus’ coat, and is also acutely touch sensitive, aiding in submarine navigation. It is vital that a platypus keeps warm as it is predominantly nocturnal and spends most of its time in the water, which tends to be colder than air.

Both, a physical and physiological adaptation of the platypus is its venomous spur (see left). Both males and females are born with it, but females shed it after about 9 months. The 12mm long spur is connected to a venom gland, and is situated on the hind foot. This spur is believed to be used as a defence and to climb the social hierarchy, especially during the mating season.

Another physiological adaptation of the platypus is that it reduces blood flow to bare and extreme parts of its body in cold weather. This keeps the vital [central] internal organs intact.

The tail of the platypus serves two main purposes. It acts as a stabilising and steering rudder underneath the water, but also stores fat. When food is scarce, or if the platypus lapses into torpor, this fat store supplies the necessary food for a certain time period.

Also, the Platypus’ kidney has evolved to dispose of water rapidly, as there is no water shortage in a platypus’ freshwater environment. However, it retains and absorbs salts with great efficiency to compensate for the lack of salt in its freshwater habitat. This salt is then used in various bodily processes.

The webbed feet of a platypus only occur on the forefeet. They extend for propulsion, but retract on the return stroke. This reduces energy expenditure, which is beneficial to the platypus.

Another physiological characteristic of the platypus is its oxygen rich blood. An increased amount of hemoglobin and red blood cells enable the platypus to remain underwater for extended periods of time – up to 14 minutes!

Changing ideas about the Platypus, and Aboriginal ideas

The Platypus has played a part in the Aboriginal dreamtime and culture

The most famous of dreamtime stories explaining the existence of the platypus is about Daroo the Duck and a Water Rat, however, it takes two different forms. The first was probably an adaptation for children to hear, while the second was the initial story.

Bilargun and Daroo

One day, a Water Rat called Bilargun was out hunting and he spotted a Duck in the distance. This duck was called Daroo, and Bilargun wanted Daroo as his wife. He snuck up on her and escorted Daroo back to his den. Here, he fed her and nurtured her. Together, they were very happy and Bilargun told Daroo that whenever she was in danger to slap her tail on the surface of the water.

After a while, Daroo had a brood, but quite an unusual one. The offspring each had 4 legs and a fur coat like their father (Bilargun), and a beak and webbed feet like their mother.

That offspring’s descendants can be seen nowadays, and they still use that same warning sign, and have the characteristics of a bird and mammal.

Bilargun and Daroo (Version 2)

Daroo the Duck lived with other ducks in a secluded pond and all were in fear of the Mulloka, or Water Devil, which lurked in deeper waters. Thus, they never strayed far from their pond. One day, however, Daroo decided to disobey the elders' advice and ventured out downstream. She stumbled across the territory of the “Water Devil”, Bilargun the Water Rat. He threatened duck with his spear when she tried to flee, and dragged her underground into his burrow. He forced her to mate with her, and remained his captive for weeks before escaping.

When it came to hatching season, all the other ducks emerged from the reeds to parade their newborn ducklings. On the other hand, Daroo was ashamed to lead out two extraordinary offspring. They had fur instead of feathers, a bill and webbed feet, and a spike on each hind leg, reminiscent of the Water Rat’s spear. Daroo was ashamed and taunted, so she left the pond with her offspring, the first of the platypuses.

Over the past 200 or so years since the first Platypus specimen was sent to England for examination in 1798, ideas about the platypus have changed considerably, from belief that it was a hoax, to a more in-depth (but nowhere near complete) knowledge of this fascinating monotreme.

The British scientist, Dr Shaw, examined the strange pelt and believed it to be a clever conglomeration of mammalian and avian body parts. However, after careful re-examinations, by 1799, it was affirmed as a genuine animal.

Initially, it was referred to as the “water mole” by settlers, but was formally named Ornithorynchus anatinus.

Since then, varying technologies have furthered our knowledge of the Platypus. A branch of mammalians known as monotremes consists of the Platypus and Echidna, Monotreme meaning “one holed” in reference to the same “hole” being used for excretion and reproduction. The biology of the Platypus has been delved into with modern technologies such as the electron microscope, and the evolution has been uncovered through the fossil record interpretation.

Over the past 20 years, intense research has gone into uncovering the breeding habits and lifestyle of this elusive creature, and though they can be very difficult to find, scientists are slowly progressing in their knowledge.

Breeding programs at organisations like zoos have recently had success in breeding platypuses in captivity, another big step in our knowledge of them.

Our ideas about the platypus have gone from one end of the spectrum, that of complete and utter disbelief, right on its way to the opposite end. The fascination of this perplexing animal motivates science to delve deeper into the life of “God’s only mistake”, the Platypus.

Technologies contributing to our knowledge of the platypus

The Platypussary

The Platypussary was an innovation developed by Dr. David Fleay, an Australian, in the late 30’s and early 1940’s. It was developed in order to stimulate the platypus’ natural habitat, in the pursuit of breeding a pair. Dr. Fleay’s Platypussary, located at the Healesville Sanctuary just outside Melbourne, consisted of natural settings and a series of tanks and pumps. Though previous attempts had been made at mimicking a stream, such as that by Eadie in the previous century, Fleay’s incorporated a series of flowing pools, filled with gravel and natural items you would expect to find in a typical Australian stream.

The significance of Dr. Fleay’s technology, the Platypussary, was that it gave rise to the first breeding pair of platypuses ever. In 1943, at Healesville, two platypuses gave birth to “Corrie”. The Platypussary had nest boxes and glass panels, making all areas accessible by keepers. The outcome of this was revolutionary research into the breeding habits of the platypus, including gestation, pre-natal and post-natal process.

The most invaluable knowledge of the platypus to date comes from the research of Healesville Platypussary, and, since then, technology has been advanced, creating almost exact replicas of the platypus’ natural environment. The birth at Healesville in 1943 was the only one until 2003. Taronga Zoo had just established its Wollemi Exhibit, a walk through enclosure mimicking the natural Eastern Australian bushland. The stream running through it, in conjunction with a first class Platypussary, led to the birth of twin Platypuses, and, again, in 2006.

The simulation of the Platypus’ natural environment was quintessential, and, through an elaborate network of pumps and filters, a life-like flowing stream, monitored closely, enabled the Platypus to be bred in captivity, thus, giving us an in-depth knowledge into the lifestyle and breeding habits of the Platypus. 

Electron Microscopy

The first Electron Microscope (left) was built in 1931 by the German engineers, Ruska and Knoll. This technology went on to advance knowledge in just about every field of science, including zoology, where it clarified the mysteries of the platypus.

Up until the 1930’s, the Platypus was observed closing its eyes, ears and nostrils when foraging underwater. This led to the question, “how do they actually find their food?”. 

The Electron Microscope enabled scientists to take a much closer look at the strange bill of the Platypus, which they noticed was vigorously swept from side to side during foraging. What was discovered about the amazing bill of the Platypus was a shock to scientists.

Thousands of ultra-sensitive touch receptors streamed messages back to the brain, helping the Platypus to navigate its way through the streams with its eyes closed. It could also be used to detect prey, if touched.

Even more alarming was the detection of Electroreceptors on the bill. These work to detect minute electrical signals, relay the message back to the brain, creating an image of the riverbed and locating prey.

Not only were these revelations due to the Electron Microscope, but a myriad of others in biology too.

Cells could be delved into in more detail, enabling scientists to examine further biological adaptations of the Platypus, such as increased hemoglobin count, salt retaining kidneys and the nervous network between the bill and the brain.

The Electron Microscope has contributed to many fields of s

The venomous spur of the Platypus, connected to a venom gland above the hind leg

Bibliography

Websites

“Platypus”, Wild Watch, < http://www.wildwatch.com.au/platypus.htm> (Unknown

date) Accessed 23/7/07

“Life and Adaptations to Water”, South Australian Museum, <

http://www.samuseum.sa.gov.au/water/platypus.htm> (Unknown date) Accessed

23/7/07

“Platypus”, DPIW, < http://www.dpiw.tas.gov.au/inter.nsf/WebPages/BHAN-

53573T?open> (11 July 2007) Accessed 21/7/07

“Historical Background and Naming”, Australian Platypus Conservancy, <

http://www.platypus.asn.au/> (Date Unknown) Accessed 23/7/07

”Electron Microscope”, Wikipedia, <

http://en.wikipedia.org/wiki/Electron_microscope> (20 July 2007) Accessed 24/7/07

Journals

Hamilton, G. (1988). “The Platypus”. Australian Geographic, Vol.12, pp50-67.

Literature

Grant, T. (1995). “The Platypus: A Unique Animal”. Sydney: UNSW

Moyal, A. (2001). “Platypus”. Sydney: Allen and Unwin

Audio-Visual

BBC., 2003. “The Life of Mammals: A Winning Design”. [DVD]. London: BBC