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Platypus-The duck-billed mammal

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Description

While fossil dating suggest that platypuses split from echidnas around 19–48 million years ago, in Europe was first encountered in 1798, when a pelt and sketch were sent back to Great Britain by Captain John Hunter, the second Governor of New South Wales.
British scientists' initial hunch was that the attributes were a hoax
Platypuses, or known as Duck-billed platypus are both bizarre looking and unusually adapted.
The Scientific name for this mammals is Ornithorhynchus anatinus.They belong to a sub-group of mammals which is called monotremes that lay eggs rather than giving birth to live young .

While it may not be the biggest, fastest, or most impressive species in the world, the little Australian mammal is certainly one of the most confusing.
The bizarre forces of evolution (which apparently love a good joke) that led to this animal have blessed it with a wide array of characteristics that you’re unlikely to find together outside a biology textbook.
The animal is best described as a hodgepodge of more familiar species: the duck (bill and webbed feet), beaver (tail), and otter (body and fur). Males are also venomous.
They have sharp stingers on the heels of their rear feet and can use them to deliver a strong toxic blow to any foe.On land, platypuses move a bit more awkwardly.
However, the webbing on their feet retracts to expose individual nails and allow the creatures to run. Platypuses use their nails and feet to construct dirt burrows at the water's edge.
The males are slightly bigger; however the biggest difference between sexes is a physiological feature that is not obvious at a glance.


Because of this competition, Platypus are basically a solitary animal. However, some may be seen in the same stretch of river where boundaries may overlap considerably, especially of the more tolerant females.
They generally live in a burrow dug into the bank, which is often dug amongst tree roots, with a very tiny entrance just above the water line (Ryan and Burwell 2000).
They can be relatively common in the streams of the tropical rainforest of Australia, but their shyness mean they can be difficult to spot. They seem more common at higher altitudes, such as on the Atherton Tablelands.

 

platypus_closed_up_


It has features of both mammals and reptiles. Like mammals, it is covered in fur, produces milk and has a four-chambered heart. Like reptiles, it lays eggs, produces vitamin C in its liver (not kidneys) and has similar kidney bones
Platypuses once swam around with dinosaurs. In Argentina, fossil remains prove that they existed at the time when the South American and Australian land masses were joined in the super-continent Gondwana.
A fossil jaw 110 million years old of a platypus prototype was found in New South Wales. However, this animal was almost twice as big and had teeth unlike the modern version. This was possibly the largest mammal in the world at that time.
It is readily distinguished from the water rat or other mammals that swim in Australian rivers and streams by its smooth swimming action, low silhouette, absence of visible ears and its rolling dive.
A covering of long flattened guard hairs give it a sleek appearance.Platypus blood is rich in oxygen-carrying haemoglobin and red blood cells, so it is able to reduce its need for oxygen by reducing its heart rate from more than 200 beats per minute to less than ten.
Living in captivity, individuals have been recorded to live for up to 17 years, and in the wild, up to at least 13 years.

 

platypus_evolution


Monotremes (for the other species, see Echidna) are the only mammals known to have a sense of electroreception: they locate their prey in part by detecting electric fields generated by muscular contractions. The platypus' electroreception is the most sensitive of any monotreme.
The electroreceptors are located in rostrocaudal rows in the skin of the bill, while mechanoreceptors (which detect touch) are uniformly distributed across the bill.
The electrosensory area of the cerebral cortex is contained within the tactile somatosensory area, and some cortical cells receive input from both electroreceptors and mechanoreceptors, suggesting a close association between the tactile and electric senses.
Both electroreceptors and mechanoreceptors in the bill dominate the somatotopic map of the platypus brain, in the same way human hands dominate the Penfield homunculus map.
The platypus can determine the direction of an electric source, perhaps by comparing differences in signal strength across the sheet of electroreceptors. This would explain the characteristic side-to-side motion of the animal's head while hunting.
The cortical convergence of electrosensory and tactile inputs suggests a mechanism for determining the distance of prey items which, when they move, emit both electrical signals and mechanical pressure pulses; the difference between the times of arrival of the two signals would allow computation of distance

 

Platypus_skeleton_

Weight varies considerably from 0.7 to 2.4 kg (1.5 to 5.3 lb), with males being larger than females: males average 50 cm (20 in) total length while females average 43 cm (17 in).
There is substantial variation in average size from one region to another, and this pattern does not seem to follow any particular climatic rule and may be due to other environmental factors such as predation and human encroachment.
The Platypus has an average body temperature of about 32 °C (90 °F) rather than the 37 °C (99 °F) typical of placental mammals.
Research suggests this has been a gradual adaptation to harsh environmental conditions on the part of the small number of surviving monotreme species rather than a historical characteristic of monotremes
The Platypus is generally regarded as nocturnal and crepuscular, but individuals are also active during the day, particularly when the sky is overcast
Dives normally last around 30 seconds, but can last longer although few exceed the estimated aerobic limit of 40 seconds. 10 to 20 seconds are commonly spent in recovery at the surface



Habitat

The duck-billed platypus is one of the strangest-looking mammals in the world. It lives in the lakes and streams of eastern Australia and has also been introduced by humans to Kangaroo Island, just off Australia's south coast.

Detailed_Map_of_Platypus_habitat


They can be viewed early morning and late afternoon at the Chambers Wildlife Rainforest Lodge platypus viewing area, or up stream from the falls besides the walking path at the Malanda Falls Environmental Park.
Other viewing areas include the bridge over Maroobi Creek, the Petersen Creek viewing area in Yungaburra and in front of the Atherton pump station on crossing road.




Feeding

Platypuses hunt underwater, where they swim gracefully by paddling with their front webbed feet and steering with their hind feet and beaverlike tail. Folds of skin cover their eyes and ears to prevent water from entering, and the nostrils close with a watertight seal.
In this posture, a platypus can remain submerged for a minute or two and employ its sensitive bill to find food.
The platypus's most famous feature, their extraordinary beak, is used to shovel up invertebrates from stream or lake beds. They also eat the occasional frog, fish, or insect taken from the water's surface.
These Australian mammals are bottom feeders. They scoop up insects and larvae, shellfish, and worms in their bill along with bits of gravel and mud from the bottom. All this material is stored in cheek pouches and, at the surface, mashed for consumption.
Platypuses do not have teeth, so the bits of gravel help them to "chew" their meal.



Breedig

The species exhibits a single breeding season; mating occurs between June and October, with some local variation taking place in populations across the extent of its range.
Male platypus are larger than the female. They reproduct by mating which occurs once a year, between June - October. The female lays between 2 - 4 eggs and incubates these for a two week period. When a young platypus is born, they feed from milk from the mother.
The mother secretes this milk from large glands under the skin, the young platypus feed from this milk which ends up on the mothers fur.

 

Platypus-wall-poster


If you thought this was a cute and cuddly Australian animal, well, you are only half correct.
Platypus reproduction is nearly unique. It is one of only two mammals (the echidna is the other) that lay eggs.
Females seal themselves inside one of the burrow's chambers to lay their eggs. A mother typically produces one or two eggs and keeps them warm by holding them between her body and her tail. The eggs hatch in about ten days, but platypus infants are the size of lima beans and totally helpless.
Females nurse their young for three to four months until the babies can swim on their own.




Evolution

The Platypus and other monotremes were very poorly understood and some of the 19th century myths that grew up around them—for example, that the monotremes were "inferior" or quasi-reptilian—still endure.
In 1947, William King Gregory theorised that placental mammals and marsupials may have diverged earlier and a subsequent branching divided the monotremes and marsupials, but later research and fossil discoveries have suggested this is incorrect.

 

Platypus_caracteristics_and_evolution


In fact, modern monotremes are the survivors of an early branching of the mammal tree, and a later branching is thought to have led to the marsupial and placental groups.Molecular clock and fossil dating suggest platypuses split from echidna around 19–48 million years ago.
The oldest discovered fossil of the modern Platypus dates back to about 100,000 years ago, during the Quaternary period. The extinct monotremes (Teinolophos and Steropodon) were closely related to the modern Platypus.
The fossilised Steropodon was discovered in New South Wales and is composed of an opalised lower jawbone with three molar teeth (whereas the adult contemporary Platypus is toothless)




Interesting facts

      Baby platypuses have teeth, but soon after leaving the burrow they lose them
    When the first platypus was shipped to Britain from Australia, people thought it was a joke and that someone had sewn a duck's bill to a mammal's body. Even when accepted as real, it was thought to be a bird or a reptile as it laid eggs.
    Platypus is one of only five living species of monotreme (the other four are species of echidna), meaning that it lays eggs rather than giving birth to live young.
    Platypuses are venomous, males having a hollow spur full of poison that can cause agonising pain in humans and kill a dog or a small animal.The defensin proteins are produced by the immune system of the platypus.

 

platypus-venom3


    Molecular clock and fossil dating suggest platypuses split from echidnas around 19–48 million years ago.
    Platypuses can consume their own body weight in food in a 24 hour period.
    A baby platypus is not called a puggle, which seems to be a common misconception. There is no official name for a baby platypus, but a common suggested name is "platypup".
    The platypus can determine the direction of an electric source, The electroreceptors are located in rostrocaudal rows in the skin of the bill, while mechanoreceptors (which detect touch) are uniformly distributed across the billand in this way they can locat the food sources under the water.

 








 

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Sources :
http://rainforest-australia.com/platypus.htm
http://animals.nationalgeographic.com/animals/mammals/platypus/
http://www.bbc.co.uk/nature/life/Platypus
http://en.wikipedia.org/wiki/Platypus
http://slices-of-life.com
http://www.bestinfographics.info
http://ristorantemystica.wordpress.com/2009/03/page/4/
http://www.ghcma.vic.gov.au/water/rivers/in-stream-habitat/

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