platypus

platypus
	Platypus ( Ornithorhynchus anatinus )
Systematics
Class :	Mammals (mammalia)
Subclass :	Ursammal (Protheria)
Order :	Monotremes (monotremes)
Family :	Platypuses
Genre :	Ornithorhynchus
Type :	platypus
Scientific name of the family
	Ornithorhynchidae
	JE Gray , 1825
Scientific name of the genus
	Ornithorhynchus
	Blumenbach , 1800
Scientific name of the species
	Ornithorhynchus anatinus
	( Shaw , 1799)

The platypus ( Ornithorhynchus anatinus , English platypus ) is an egg-laying mammal from Australia . It is the only living species in the platypus family (Ornithorhynchidae). Together with the four types of Ameisenigel it forms the taxon of monotremes (monotremes) extending as basal group greatly different from all other mammals.

features

General

The body structure of the platypus is flattened and streamlined , it has certain similarities with a flat-built beaver and also has a comparatively flat tail . The body and tail are covered with brown, water-repellent fur. The feet are webbed. The body length of platypus is around 30 to 40 centimeters, the tail, which is used as a fat store, is 10 to 15 centimeters long. Platypuses reach a weight of 0.5 to 2.5 kilograms, with males being around a third larger than females. As with all monotons, both excretory and sexual organs flow into a common opening, the " cloaca ".

Dimensions of different areas of origin
		Northern Queensland	Southeast Queensland	New South Wales
		Northern Queensland	Southeast Queensland	east of the Dividing Range	Dividing range	west of the Dividing Range
Total length	male	44.1 cm	49.3 cm	50.5 cm	47.4 cm	54.9 cm
Total length	female	41.0 cm	43.8 cm	41.5 cm	40.3 cm	47.0 cm
Weight	male	1018 g	1556 g	1434 g	1379 g	2215 g
Weight	female	0704 g	1222 g	0857 g	0888 g	2000 g

Compared to other mammals, the body temperature of the platypus is very low at around 32 degrees Celsius. Whether this fact was typical for egg-laying mammals or a special adaptation to the way of life can hardly be answered due to the few surviving species of monotremes.

Head and beak

Skeleton of a platypus

The German name of the animal already suggests its most conspicuous characteristic, the flexible beak, which is similar in shape to that of a duck and whose surface has the texture of smooth cowhide. Adult platypus have no teeth, only horn plates on the upper and lower jaw, which are used to grind food. At birth, the animals still have three-pointed molars, but they lose them in the course of their development. In order to be able to use the beak effectively, the chewing muscles of the animals are modified. The nostrils are fairly far forward on the upper beak; this enables the platypus to breathe according to the “ snorkel ” principle when largely submerged . The construction of the lower jaw shows similarities with reptilian ancestors. In contrast to these, the three ossicles ( hammer , anvil and stirrup ), which form parts of the jaw in reptiles, are, however, firmly integrated in the skull. This is a characteristic that all mammals have in common. However, the ear opening is very close to the lower jaw compared to other mammals. In contrast to all other mammals, platypus also have additional bones in the shoulder girdle .

Poison spurs

Hind foot of a platypus with poisonous spurs

The male platypus is one of the few poisonous mammals . They have about 15 millimeters long poisonous spurs at ankle height on their hind legs. These excrete a poison that is produced in glands in the abdomen. Female animals also have spurs at birth, but lose them in the first year of life. Since the venom is only produced during the mating season, it is believed that it is primarily used in the fight for a female ready to mate.

The poison comprises a peptide , the amino-terminal to the C-type natriuretic peptide (CNP, a vasodilatatives peptide having natriuretic action merely indirectly) homolog is. Another five proteins and peptides have been identified in the venom of the platypus : defensin-like peptides (DLPs), Ornithorhynchus venom C-type natriuretic peptides (OvCNPs), Ornithorhynchus nerve growth factor , hyaluronidase and l-to-d-peptide isomerase . The poison is not fatal for humans, but causes very painful swellings, which can hardly be reduced even with high doses of morphine and which can last for several months. From the time when platypuses were still hunted for their fur , there are reports that dogs that were supposed to catch wounded animals died from the poison. How the poison affects other platypuses is not known; However, since it is not used for defense against predators, but in rival fights, its mode of action is probably not designed for death, but for injury.

Karyotype and genome

In 2004, another peculiarity of the platypus was discovered: it has 10 sex chromosomes , the females 10 X chromosomes and the males 5 X and 5 Y chromosomes, while most other mammals (including humans) only have two of these (XX in females and XY in males). In some respects the chromosomal system of these animals is similar to that of birds , but they evolved independently from mammals. The platypus genome is organized into 21 autosomes and 10 sex chromosomes within the cell nucleus, as well as in the mitochondrial genome .

The full genome of a female New South Wales animal was first analyzed in 2007; it consists of 1,995,607,322 base pairs . The exact number of genes (initially estimated at 18,600) is still unknown. Among other things, the platypus shares typical milk production proteins with other mammals, but it also has special genes associated with egg reproduction. The poison proteins of the platypus developed independently of the poison system of the reptiles ( Toxicofera ). What is striking is the large number of genes that code for receptor proteins for olfactory perception under water.

Distribution area:

Home

Settled

distribution

Platypuses inhabit freshwater systems of eastern and southeastern Australia . They prefer clean, standing or flowing water. Their distribution area extends over the states of Queensland , New South Wales , Victoria and the island of Tasmania . They were successfully settled on Kangaroo Island .

Way of life

General

Platypuses are nocturnal loners. They are excellent swimming and spend most of their lives in the water . Both eyes and ear openings are closed underwater . To move forward underwater, they paddle with their front legs, while the hind legs and flat tail are used for steering. When they are not in the water, they withdraw into earth burrows. These are mostly located on embankments, the entrance is just above the water surface and is hidden by plants. Platypuses dig their burrows with their strong front paws, whereby they can fold their webbed feet upwards. A special feature here is the use of their broad tail as a transport medium, under which platypuses can clamp building material such as twigs and transport them rolled up to the building, whereby the beak remains free on the way for other tasks. They usually have several burrows that they use alternately. In cold weather, platypuses sometimes go into a cold rigor, the so-called torpor, for several days . If necessary, platypus can move unexpectedly quickly on land. The left front and right rear legs or the right front and left rear legs are exactly synchronized in their movement; this cloister is also known from many lizards .

nutrition

Illustration from the 19th century

Platypuses are carnivores and their diet consists primarily of crabs , insect larvae and worms . They look for their food underwater. To do this, they take a deep breath and go underground; this way they can stay underwater for around two minutes. They find their food by swimming in the water or by digging in the mud with their beak or by turning stones with it.

While eyes are closed underwater, platypuses use electroreceptors and mechanoreceptors on their beak to find prey. These sensors are among the most effective of all mammals. With the help of their electroreceptors, they can feel the weak electrical fields that arise when the prey animals' muscles move; the tactile corpuscles react to the finest wave movements. Since both perception functions are closely linked, platypus can precisely determine the location and distance of the prey based on the time difference between electrical and tactile impulses and snap shut with pinpoint accuracy . Three variables are of essential importance for identifying the prey: the strength of the electrical output signals, the propagation of the signals in the water and the sensitivity of the platypus. An amplitude and frequency analysis showed that the respective values differed greatly according to prey: The worm Lubricus ssp. hunted at an amplitude of 3 μV / cm at an equivalent frequency of (3 Hz) and giant bugs (Belostomatidae) at an amplitude of 800 μV / cm and a frequency of 20 Hz. Platypuses have thus developed an efficient search system, the exact details of which, however, have not yet been fully clarified. Once they have found food, it is stowed in cheek pouches and only eaten after the animals have returned to the surface.

Reproduction

Platypuses are solitary outside of the mating season. For mating, which takes place in the Australian late winter or spring (July to October), the female approaches the male and repeatedly brushes his fur, then the male grabs the female's tail with his beak and they swim in a circle. Mating also takes place in the water, with the male inserting his penis into the female cloaca. To raise the young, the female digs larger earthworks, sometimes up to 20 meters long. The “kettle” at the end is upholstered with soft plant parts. For transport, the nesting material is clamped with the tail folded under the trunk. Around 12 to 14 days after mating, the female usually lays three white, soft eggs . With their large yolk and parchment-like shell, they look more like reptile eggs than bird eggs. The eggs are incubated for around 10 days; the young come out of the egg naked and with their eyes closed and are around 25 millimeters tall. After hatching, they are nourished with breast milk , which is secreted by glands in the breast area (transformed sweat glands), the milk field . Since the females have no teats , the young lick the milk from the mother's fur. The male does not participate in rearing. The young remain in their mother's den for about five months, but are still fed by the mother afterwards.

Platypuses reach sexual maturity at around two years of age. The highest known age of a specimen in captivity was 17 years and life expectancy in the wild is unknown; Estimates run for five to eight years.

Natural enemies

The natural enemies of platypus include the Murray cod , large birds of prey , the colored monitor lizard and diamond pythons ; Introduced predators such as red foxes also occasionally hunt platypuses. The gold-bellied swimming rat , which is similar in body and way of life to the platypus, sometimes refers to their burrows and eats young animals.

Platypuses and humans

According to an Aboriginal legend, platypuses are the descendants of a female duck and a male swimming rat . They have the beak and webbed feet from their mother, and their brown fur from their father.

"A disbeliever in anything beyond his own reason, might exclaim: Surely two distinct creators must have been at work."

"If someone only believes his own understanding, he could exclaim: Certainly two different creators must have been at work here."

- Charles Darwin : Charles Darwin, diary entry (January 1836)

A bagwolf attacks a platypus, illustration from Cassell's Natural History (1854)

The first European settlers saw these animals in the late 18th century. When they sent a hide to London, it was initially thought to be a joke, the work of a skilled taxidermist. The first scientific description of the animals was made in 1799 by George Shaw in London . He based his investigation on a bellows and a few drawings that were believed to have been sent to England by Captain John Hunter of the Royal Navy, who was governor of the penal colony in New South Wales. Still, Shaw's first description was surprisingly accurate. Biologists later took an interest in the animal. Research into platypus was made difficult by the extremely difficult nature of them to keep in human captivity, and details about their reproduction did not emerge until the early 20th century. Until the beginning of the 20th century, they were hunted for their fur. In some regions of Australia, for example in South Australia , they have disappeared, in others they have become rare due to human settlement and river regulations. As with other animal species, sharp-stranded nets and blocking quivers pose a particular danger for platypus, as they can get caught in them and injure themselves and often cannot avoid these obstacles when crossing their natural habitat. However, these risks can be reduced through the use of animal and environmentally friendly fishing methods. Platypuses prefer clean water and generally avoid human proximity; nevertheless, they are sometimes found in human settlements, while they do not occur in waters that should actually be comfortable for them.

Platypuses are now fully protected; Because of their habitat requirements, they are classified in Australia as “common, but vulnerable” . Private individuals are not allowed to keep platypus, zoos need a special permit. The keeping of these animals is classified as difficult due to the high demands on the habitat; in the 19th century almost all animals kept in human captivity died. Only recently has it been possible to gain the necessary knowledge for species-appropriate and successful husbandry. These difficulties are also evidenced by the fact that - apart from a single case and the first breeding in 1943 at Victoria Zoo - it was only possible to breed the animals in captivity more often from 1998 onwards. The privilege of keeping is now reserved for only a few institutions, including Victoria and Sydney Zoo. Due to the high demand for food, the cost of the feed is particularly high. The systems, which are specially insulated for keeping electrical waves, often give visitors an underwater view. The export of live animals from Australia is completely prohibited. In Europe, only Rotterdam and Leipzig come into consideration as potential former owners.

The platypus is the epitome of the biological curiosity, which is expressed for example in the book title Kant and the platypus by Umberto Eco . Was also known Robert Hardt Gern eponymous poem, published u. a. in Reim und Zeit , Reclam, Stuttgart 2001. In the introduction to the film Dogma from 1999, the platypus is given as an example of the fact that God must have a sense of humor.

Systematics and history of development

Platypus in the Broken River in Queensland

Skull of Obdurodon dicksoni in the American Museum of Natural History in New York

The platypus is considered a living fossil . Unlike the modern mammals and marsupials put the monotremes eggs, one of the considered as ethnic characteristics that gives them the name " Ursäuger has introduced". Platypuses and their relatives, the Echidna , share three characteristic mammalian features: the three ossicles (hammer, anvil and stapes), the presence of hair and the feeding of the young with milk . Although the earliest mammals were likely to lay eggs, platypuses are not the ancestors of the sac or placenta animals , but rather represent a specialized side branch.

The fossil history of platypus relatives is poorly documented. The oldest known fossils date from the Cretaceous Period and were found in southeastern Australia . These are jawbones of the genera Steropodon and Teinolophos , which are probably close relatives of the recent platypus. The jawbones still had molars , but were comparable in size to those of today's animals. A genus from the Miocene , Obdurodon , still had teeth. In Argentina , teeth from the Paleocene period have been found that resemble those of Obdurodon and are very clearly identifiable as teeth of a closely related species; however, they were twice as big. The corresponding animal was called Monotrematum sudamericanum , it is so far the only non-Australian find of a platypus relative. The oldest finds of the genus Ornithorhynchus are around 4.5 million years old; no evidence of today's platypus has been found that is more than 100,000 years old.

literature

ML Augee: Platypus and Echidnas. The Royal Zoological Society, New South Wales 1992, ISBN 0-9599951-6-1 .
Ronald Strahan: Mammals of Australia . Smithsonian Press, Washington DC 1996, ISBN 1-56098-673-5 .
NG Taylor, PR Manger, JD Pettigrew, LS Hall: Electromagnetic potentials of a variety of platypus prey items: an amplitude and frequency analysis . In: LM Augee: Platypus and Echidnas. 1992, ISBN 0-9599951-6-1 , pp. 216-224.
TR Grant: Fauna of Australia . 16. Ornithorhynchidae online publication as PDF ( Memento from November 9, 2006 in the Internet Archive )
Walter Fiedler (Ed.): Mammals . In: Grzimek's animal life . Volume 10, Droemer Knaur, Munich 1967. (Bechtermünz, Augsburg 2000, ISBN 3-8289-1603-1 )
Ann Moyal: Platypus. The Extraordinary Story of How a Curious Creature Baffled the World . Smithsonian Press, Washington DC 2001, ISBN 1-56098-977-7 .
Ulrich Zeller: The development and morphology of the skull of Ornithorhynchus anatinus . (Mammalia: Prototheria: Monotremata), In: Senckenbergische Naturforschende Gesellschaft: Treatises of the Senckenbergische Naturforschende Gesellschaft. Volume 545, Kramer, Frankfurt am Main 1989, ISBN 3-7829-2548-3 . (Also habilitation thesis at the Georg-August-Universität Göttingen )

Individual evidence

^ NF Carrick In: R. Strahan: The complete book of Australian mammals. 1991, ISBN 0-207-14454-0 , p. 38.
^ G. de Plater, R. L Martin, PJ Milburn: A pharmacological and biochemical investigation of the venom from the platypus (Ornithorhynchus anatinus). In: Toxicon , Vol. 33, No. 2, February 2, 1995, pp. 157-169, doi : 10.1016 / 0041-0101 (94) 00150-7 .
↑ Jennifer MS Koh, Paramjit S. Bansal, Allan M. Torres, Philip W. Kuchel: Platypus venom: source of novel compounds. In: Australian Journal of Zoology 57, No. 4, 2009, pp. 203-210, doi : 10.1071 / ZO09040 .
↑ Richard Dawkins : Stories from the Origin of Life . Ullstein Verlag, 2008, ISBN 978-3-550-08748-6 .
↑ MapViewer entry
^ WC Warren, LW Hillier, JA Marshall Graves et al: Genome analysis of the platypus reveals unique signatures of evolution . In: Nature . 453, No. 7192, May 2008, pp. 175-183. doi : 10.1038 / nature06936 . PMID 18464734 . PMC 2803040 (free full text).
↑ Frank Gruetzner, Willem Rens a. a .: In the platypus a meiotic chain of ten sex chromosomes shares genes with the bird Z and mammal X chromosomes. In: Nature. 432, 2004, pp. 913-917, doi : 10.1038 / nature03021 .
↑ ^a ^b N. G. Taylor et al. 1992
^ [1] , Darwin's Diary January 1836
↑ imdb.com: Dogma (1999) - Crazy credits . Accessed December 4, 2010.