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Tassie 1/22 & 23

Friday, January 24, 2014

Well first things first. A bright and early morning it was. For a good reason as well. We went on a tour to see Duck Bill Platypus. They are such interesting creatures. It's like they can't make up their minds. Bills like a duck, Fur instead of feathers and tails like beavers. Not to mention the Spurs that the males have. But I am ahead of myself.

The tour started out really early in the morning. The sun was up but my brain was not. They did provide Tea & Coffee which helped. There were also breakfast type nibbles as well. They drove us to a trail head and then the "walk" ensued. It was very hard and difficult too. But the glorious pool at the end of the "hike" was well worth it.



We all arranged ourselves around it and waited for the magic to happen. It didn't take long. While we waited they gave us some information on the Platypus.

The platypus is a semiaquatic mammal that lives in eastern Australia, including Tasmania. Together with the four species of echidna, it is one of the five extant species of monotremes, the only mammals that lay eggs instead of giving birth.


Platypus eggs

Monotremes (from the Greek monos "single" + trema "hole", referring to the cloaca) are mammals that lay eggs (Prototheria) instead of giving birth to live young like marsupials (Metatheria) and placental mammals (Eutheria). The only surviving examples of monotremes are all indigenous to Australia and New Guinea, although there is evidence that they were once more widespread. Among living mammals, they comprise the platypus and four species of echidnas (or spiny anteaters). There is currently some debate regarding monotreme taxonomy. Monotreme young are sometimes called puggles.

Like other mammals, monotremes are warm-blooded with a high metabolic rate (though not as high as other mammals); have hair on their bodies; produce milk through mammary glands to feed their young; have a single bone in their lower jaw; and have three middle-ear bones.

Monotremes lay eggs. However, the egg is retained for some time within the mother, which actively provides the egg with nutrients. Monotremes also lactate, but have no defined nipples, excreting the milk from their mammary glands via openings in their skin. All species are long-lived, with low rates of reproduction and relatively prolonged parental care of infants.

Extant monotremes lack teeth as adults. Fossil forms and modern platypus young have a "tribosphenic" form of molars (with the occlusal surface formed by three cusps arranged in a triangle), which is one of the hallmarks of extant mammals. Some recent work suggests that monotremes acquired this form of molar independently of placental mammals and marsupials, although this is not well established. Monotreme jaws are constructed somewhat differently from those of other mammals, and the jaw opening muscle is different. As in all true mammals, the tiny bones that conduct sound to the inner ear are fully incorporated into the skull, rather than lying in the jaw as in cynodonts and other premammalian synapsids; this feature, too, is now claimed to have evolved independently in monotremes.



The monotremes also have extra bones in the shoulder girdle, including an interclavicle and coracoid, which are not found in other mammals. Monotremes retain a reptile-like gait, with legs on their sides of, rather than underneath, their bodies. The monotreme leg bears a spur in the ankle region; the spur is not functional in echidnas, but contains a powerful venom in the male platypus.



The Platypus are the sole living representative of its family (Ornithorhynchidae) and genus (Ornithorhynchus), though a number of related species have been found in the fossil record.

The unusual appearance of this egg-laying, duck-billed, beaver-tailed, otter-footed mammal baffled European naturalists when they first encountered it, with some considering it an elaborate fraud. It is one of the few venomous mammals, the male platypus having a spur on the hind foot that delivers a venom capable of causing severe pain to humans. The unique features of the platypus make it an important subject in the study of evolutionary biology and a recognizable and iconic symbol of Australia; it has appeared as a mascot at national events and is featured on the reverse of its 20-cent coin. The platypus is the animal emblem of the state of New South Wales.

Until the early 20th century, it was hunted for its fur, but it is now protected throughout its range. Although captive breeding programs have had only limited success and the platypus is vulnerable to the effects of pollution, it is not under any immediate threat.

While both male and female platypuses are born with ankle spurs, only the male's spurs produce venom, composed largely of defensin-like proteins (DLPs), three of which are unique to the platypus. The DLPs are produced by the immune system of the platypus. Although powerful enough to kill smaller animals such as dogs, the venom is not lethal to humans, but the pain is so excruciating that the victim may be incapacitated. Edema rapidly develops around the wound and gradually spreads throughout the affected limb. Information obtained from case histories and anecdotal evidence indicates the pain develops into a long-lasting hyperalgesia (a heightened sensitivity to pain) that persists for days or even months. Venom is produced in the crural glands of the male, which are kidney-shaped alveolar glands connected by a thin-walled duct to a calcaneus spur on each hind limb. The female platypus, in common with echidnas, has rudimentary spur buds which do not develop (dropping off before the end of their first year) and lack functional crural glands.
Since only males produce venom and production rises during the breeding season, it may be used as an offensive weapon to assert dominance during this period.


Close up of Spur


Showing the sac holding the venom

Monotremes (for the other species, see Echidna) are the only mammals (apart from at least one species of dolphin) 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.


Showing the shorter lower "bill"

The platypus feeds by neither sight nor smell, closing its eyes, ears, and nose each time it dives. Rather, when it digs in the bottom of streams with its bill, its electroreceptors detect tiny electrical currents generated by muscular contractions of its prey, so enabling it to distinguish between animate and inanimate objects, which continuously stimulate its mechanoreceptors. Experiments have shown the platypus will even react to an "artificial shrimp" if a small electrical current is passed through it.

Recent studies say that the eyes of the platypus could possibly be more similar to those of Pacific hagfish or Northern Hemisphere lampreys than to those of most tetrapods. Also it contains double cones, which most mammals do not have.


Platypus eyes

Although the platypus' eyes are small and not used under water, several features indicate that vision played an important role in its ancestors. The corneal surface and the adjacent surface of the lens is flat while the posterior surface of the lens is steeply curved, similar to the eyes of other aquatic mammals such as otters and sea-lions.

After our wonderful outing I chose to rest since the next day was going to be very busy!

After a wonderful dinner of all the fresh vegetables one could eat I had a great sleep and was up bright and early ready for our flight. It was only a 2 hour flight and the plane was a small plane and seemed to be mostly filled by our group. That was great so we could chat the whole way there!

To Be Continued
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  Member Comments About This Blog Post:

JAOTAO 1/24/2014 11:54AM

    Wow - what an informative blog! Thanks for posting this!

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EMMABE1 1/24/2014 4:14AM

    Great - I have actually never seen a platypus in the wild - they are very timid - I have seen them in wildlife parks though!! Interesting animals!!

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