platypus n : small densely furred aquatic monotreme of Australia and Tasmania having a broad bill and tail and webbed feet; only species in the family Ornithorhynchidae [syn: duckbill, duckbilled platypus, duck-billed platypus, Ornithorhynchus anatinus]

English

Etymology

From Modern Latin Platypus (originally a genus name, but already used for a type of beetle), from Greek πλατύπους ‘flat-footed’, from πλατύς ‘flat’ + πούς ‘foot’.

Noun

platypus (plural: platypuses, platypi or platypus; rare, pedantic: platypodes)

1. An egg-laying, semiaquatic mammal with a bill resembling that of a duck, a mole-like body, a tail resembling that of a beaver, a waterproof pelt, and flat webbed feet — males have poisonous spurs on the inside of the back legs. The platypus (Ornithorhynchus anatinus) lives in the freshwater streams of Tasmania and eastern mainland Australia.

   Victoria's Healesville Sanctuary is celebrating the births of two baby platypuses, in a major milestone. — ABC News, March 2 2008

Synonyms

• duck-billed platypus
• duckbill
• duckmole
• watermole

Translations

Quotations

Singular platypus

• 1779, George Shaw, The Naturalist's Miscellany: Or, Coloured Figures Of Natural Objects; Drawn and Described Immediately From Nature

  The Platypus is a native of Australia or New Holland, and is at present in the possession of Mr. Dobson, so much distinguished by his exquisite manner of preparing specimens of vegetable anatomy.

Plural form platypuses

• 1958, Richard H. Manville, Concerning Platypuses, in Journal of Mammology, Vol. 39, No. 4

  For the past ten years the only living duck-billed platypuses, Ornithorhynchus anatinus, outside their native Australia and Tasmania were the two in the collection of the New York Zoological Society.

Plural form platypi

• 1832, On the Mammary Glands of the Ornithorhynchus paradoxus, in Philosophical Transactions of the Royal Society of London, Vol. 122

  In the insides of several female Platypi which were shot, eggs were found of the size of a large musket-ball and downwards, imperfectly formed however, i. e. without the hard outer shell, which prevented their preservation. Several young Platypi were obtained and put into spirits, in which state they are forwarded.

Plural form platypus

• 1998, Paul R. Manger, Leslie S. Hall & John D. Pettigrew, The Development of the External Features of the Platypus (Ornithorhynchus Anatinus), in Philosophical Transactions: Biological Sciences, Vol. 353, No. 1372

  In this study, the examination of 33 nestling platypus was undertaken, which represents the largest collection of nestling platypus examined in any single study. The ages of these platypus ranged from the day of hatching through to approximately 6 months of age.

Plural form platypodes

• 2001: Peter Mackay, Native Animal Recipes? in canb.general http://groups.google.com/group/canb.general/browse_thread/thread/75d2e8cbedc51a73/3ff147e2b034aed8?lnk=st&q=&rnum=28#3ff147e2b034aed8

  Anyway, kangaroos evolved here, as did platypodes and a whole bunch of other birds and animals and fish and plants. Murray Cod. Emu. Macadamias.

See also

• echidna
• monotreme

The Platypus (Ornithorhynchus anatinus) is a semi-aquatic mammal endemic to 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 to live young. It is 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 bizarre appearance of this egg-laying, venomous, 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 has 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 the Australian 20 cent coin.

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.

Taxonomy and etymology

When the Platypus was first discovered by Europeans in 1798, a pelt and sketch were sent back to the United Kingdom by Captain John Hunter, the second Governor of New South Wales. The British scientists were at first convinced that the attributes must have been a hoax. It was thought that somebody had sewn a duck's beak onto the body of a beaver-like animal. Shaw even took a pair of scissors to the dried skin to check for stitches. Shaw assigned it as a Linnaean genus name when he initially described it, but the term was quickly discovered to already belong to the wood-boring ambrosia beetle (genus Platypus). It was independently described as Ornithorhynchus paradoxus by Johann Blumenbach in 1800 (from a specimen given to him by Sir Joseph Banks) and following the rules of priority of nomenclature it was later officially recognised as Ornithorhynchus anatinus.

Description

The body and the broad, flat tail of the Platypus are covered with dense brown fur that traps a layer of insulating air to keep the animal warm. and fat-tailed sheep). It has webbed feet and a large, rubbery snout; these are features that appear closer to those of a duck than to those of any known mammal. The webbing is more significant on the front feet and is folded back when walking on land.

The Platypus has an average body temperature of 31–32 °C (88–90 °F) rather than the 37 °C (100 °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.

Modern Platypus young have three-cusped molars which they lose before or just after leaving the breeding burrow; adults have heavily keratinised pads in their place. Although powerful enough to kill smaller animals, 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.

The electroreceptors are located in rostro-caudal 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 animal's characteristic side-to-side motion of its 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, which would also allow for computation of distance from the difference in time of arrival of the two signals.

Ecology and behaviour

The Platypus is semi-aquatic, inhabiting small streams and rivers over an extensive range from the cold highlands of Tasmania and the Australian Alps to the tropical rainforests of coastal Queensland as far north as the base of the Cape York Peninsula. Inland, its distribution is not well known: it is extinct in South Australia (barring an introduced population on Kangaroo Island) and is no longer found in the main part of the Murray-Darling Basin, possibly due to the declining water quality brought about by extensive land clearing and irrigation schemes. Along the coastal river systems, its distribution is unpredictable; it appears to be absent from some relatively healthy rivers, and yet maintains a presence in others that are quite degraded (the lower Maribyrnong, for example).

In captivity Platypuses have survived to seventeen years of age and wild specimens have been recaptured at eleven years old. Mortality rates for adults in the wild appear to be low. The introduction of red foxes as a predator for rabbits may have had some impact on its numbers on the mainland. Its habitat bridges rivers and the riparian zone for both a food supply of prey species and banks where it can dig resting and nesting burrows.

The Platypus is an excellent swimmer and spends much of its time in the water foraging for food. When swimming it can be distinguished from other Australian mammals by the absence of visible ears. Uniquely among mammals it propels itself when swimming by alternate rowing motion with the front two feet; although all four feet of the Platypus are webbed, the hind feet (which are held against the body) do not assist in propulsion, but are used for steering in combination with the tail. The species is endothermic, maintaining its body temperature about 32 °C, lower than most mammals, even while foraging for hours in water below 5 °C (41 °F). The Platypus is a carnivore: it feeds on annelid worms and insect larvae, freshwater shrimps, and yabbies (freshwater crayfish) that it digs out of the riverbed with its snout or catches while swimming. It utilizes cheek-pouches to carry prey to the surface where they are eaten. Females are thought likely to become sexually mature in their second year, with breeding confirmed to still take place in animals over nine years old. The male takes no part in caring for its young, and retreats to its yearlong burrow. The female softens the ground in the burrow with dead, folded, wet leaves and she fills the nest at the end of the tunnel with fallen leaves and reeds for bedding material. This material is dragged to the nest by tucking it underneath her curled tail. The eggs develop in utero for about 28 days with only about 10 days of external incubation (in contrast to a chicken egg which spends about 1 day in tract and 21 days externally). During the second, the digits develop, and in the last, the egg tooth appears.

The newly hatched young are vulnerable, blind, and hairless, and are fed by the mother's milk. Although possessing mammary glands, the Platypus lacks teats. Instead, milk is released through pores in the skin. There are grooves on her abdomen that form pools of milk, allowing the young to lap it up. After about five weeks, the mother begins to spend more time away from her young and at around four months the young emerge from the burrow. In fact, modern monotremes are the survivors of an early branching of the mammal tree; a later branching is thought to have led to the marsupial and placental groups.

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.

Because of the early divergence from the therian mammals and the low numbers of extant monotreme species, it is a frequent subject of research in evolutionary biology. In 2004, researchers at the Australian National University discovered the Platypus has ten sex chromosomes, compared with two (XY) in most other mammals (for instance, a male Platypus is always XYXYXYXYXY). Although given the XY designation of mammals, the sex chromosomes of the Platypus are more similar the ZZ/ZW sex chromosomes found in birds. It also lacks the mammalian sex-determining gene SRY, meaning that the process of sex determination in the Platypus remains unknown. A draft version of the platypus genome sequence was published in Nature on 8 May 2008 revealing both reptilian and mammalian elements, as well as two genes found previously only in birds, amphibians and fish. Until recently the introduced Red Fox (Vulpes vulpes) was confined to mainland Australia, but growing evidence now indicates that it is present in low numbers in Tasmania. This efficient, adaptable predator is recognised in Australia as the single most devastating introduced pest and threat to Australia's native land animals. It would be a disaster to native biodiveristy if it was allowed to establish in Tasmania. Tasmania arguably represents the best habitat for platypus in Australia and probably has the highest numbers of platypus of any state. Fungal disease and fox predation may represent significant challenges to these iconic animals.

Much of the world was introduced to the Platypus in 1939 when National Geographic Magazine published an article on the Platypus and the efforts to study and raise it in captivity. This is a difficult task, and only a few young have been successfully raised since — notably at Healesville Sanctuary in Victoria. The leading figure in these efforts was David Fleay who established a platypussary — a simulated stream in a tank — at the Healesville Sanctuary and had a successful breeding in 1943. In 1972, he found a dead baby of about 50 days old, which had presumably been born in captivity, at his wildlife park at Burleigh Heads on the Gold Coast, Queensland. Healesville repeated its success in 1998 and again in 2000 with a similar stream tank. Taronga Zoo in Sydney bred twins in 2003, and had another birth in 2006.

Cultural references

The Platypus is sometimes jokingly referred to as proof that God has a sense of humor (at the beginning of the film Dogma for example). Its unusual appearance has led to it featuring in many media, particularly in its native Australia.

The Platypus has been used several times as a mascot: "Syd" the Platypus was one of the three mascots chosen for the Sydney 2000 Olympics along with an echidna and a kookaburra, "Expo Oz" the Platypus was the mascot for Expo '88 which was held in Brisbane in 1988, and Hexley the Platypus is the mascot for Apple Computer's BSD-based Darwin operating system, Mac OS X.

The Platypus has also been featured in songs, such as Green Day's Platypus (I Hate You), and frequently appears as a character in children's programmes, for example, the Platypus Family on Mister Rogers’ Neighborhood, and Ovide, the star of the cartoon Ovide and the Gang.

See also

• Australian fauna
• List of venomous mammals
• Henry Burrell

Notes

References

• Augee, Michael L. Platypus. World Book Encyclopedia. 2001 ed.
• Burrell, H. The Platypus. Adelaide: Rigby, 1974.
• Marshall, Ben "The Amazing Duckbilled Platypus" New York Publishers Inc. 2002 ed
• Grant, Tom. The platypus: a unique mammal. Sydney: University of New South Wales Press, 1995. ISBN 0-86840-143-9.
• Griffiths, Mervyn. The Biology of the Monotremes. Academic Press, 1978.
• Michael Hutch, Melissa C. McDade, eds. Grzimek's Animal Life Encyclopedia; Volume 12. Detroit: Gale, 2004.
• Moyal, Ann. Platypus: The Extraordinary Story of How a Curious Creature Baffled the World. Smithsonian Books, 2001. ISBN 1-56098-977-7.
• Strahan, R. The Mammals of Australia. New South Wales: Reed Books, 1995.

• Eye of the Storm. Documentary by the Australian Broadcasting Corporation.

External links

• Nature.com "Top billing for platypus at end of evolution tree" 7 May 2008
• PBS.org
• Platypus-Evolution and Conservation

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