Platypus Genome Is As Weird As It Looks

New Scientist ^ | 5-7-2008 | Emma Young

[blam]

Platypus genome is as weird as its looks

18:00 07 May 2008
NewScientist.com news service
Emma Young

It's part-reptile, part-mammal, part-bird – and totally unique. Two centuries after European scientists deemed a dead specimen so outlandish it had to be a fake, the bizarre genetic secrets of Australia's platypus has been laid bare.

Platypuses lay eggs and produce venom like some reptiles, but they sport furry coats and feed their young with milk like mammals. The odd creatures are classed as monotremes, with only one close relative – the echidna.

But as primitive mammals that share the same ancestor as humans, a study of the animal's genome can improve biologists' understanding of how mammals evolved, while illuminating the platypus's strange physiology.

Wesley Warren at Washington University in St Louis, Missouri, led the international team that sequenced the platypus genome. As expected, they found an amalgam of some ancestral reptile and some newer mammalian features. But there were also surprises.

Ancient milk

And while the gene that the human sex-determining gene evolved from is present in the platypus genome, it seems to have nothing to do with sex determination. So, that function must have evolved after the platypus split from our common ancestor, about 166 million years ago.

However, by that time, milk production was well-evolved. The platypus has the same repertoire of milk protein genes as a cow or a human. Clearly, milk evolved long before we evolved to give birth to live offspring, says team member Jenny Graves at the Australian National University in Canberra.

The team also investigated the genes for the platypus toxin, which males deliver via a barbed spur on their heel. While the toxin is similar to a snake's – adapted from natural neurotransmitters and other proteins –

[blam]

The duck-billed platypus, Ornithorhynchus anatinus, found only in eastern Australia, lives in streams, rivers, and occasionally lakes with year-round water. It feeds mostly on bottom-dwelling aquatic insect larvae, which it finds by probing the streambed with its pliable, sensitive bill. It grows to a maximum size of 1 to 2.4 kg (2.2 to 5.3 lb). One of only a few venomous mammals, the male platypus has a poison gland in the hind leg that opens through a bony spur on the ankle. The spur is used to defend against predators and possibly to defend its territory against other males. The females lack the venom gland and bony spur.

[blam]

Echidna

[ClearCase_guy]

Clearly, milk evolved long before we evolved to give birth to live offspring, says team member Jenny Graves at the Australian National University in Canberra.

Sounds logical. Must be true.

[Abathar]

The good lord sure fiddled when he should have faddled when it comes to those things.

Not one of his more beautiful creations IMO...

[Dr. Bogus Pachysandra]

Fascinating animal! Caused by global warming in the distant past. Now again threatened by global warming. Manmade Global Warming will cause it to mutate into it’s giant form, weighing in at 250-400 kilos, with a duck’s bill, a beaver’s tail, and cloven hooves. And it’s your fault!

[Dr. Bogus Pachysandra]

Also, it’s diet will consist of women and children, at first.

[najida]

An animal designed by a committee.

[lesser_satan]

I think the platypus was designed by committee.

[lovecraft]

Take a beaver and slap on a duck's bill....

The platypus: proof that God gets stoned. It's a mammal, but lays eggs....Screw you Darwin! :-)

credit to Robin Williams for the jokes.

[Blood of Tyrants]

A nice story but there is absolutely no evidence that the platypus evolved from anything. Not one fossil of a platypus-like (but not a platypus) creature has ever been found.

[HoustonTech]

Thanks for the picture. After all these years just now I learn what an enchilada is made from.

[lesser_satan]

dammit, you beat me to it.

[HoustonTech]

Not one of his more beautiful creations IMO...

I don't know. If you were a Platypus, you might like your looks. ;-)

[TexGuy]

Clearly, milk evolved long before we evolved to give birth to live offspring, says team member Jenny Graves at the Australian National University in Canberra.

Sounds logical. Must be true.

and ... The milk-delivery system had to evolve before milk since because the male would not even talk to the females prior to the evolution of said delivery system so no offspring could ever have been conceived.

[theFIRMbss]

Where is the pic of
Emo Platypus Needs Love   ?
The net's lost its edge . . .

[Soliton]

A nice story but there is absolutely no evidence that the platypus evolved from anything. Not one fossil of a platypus-like (but not a platypus) creature has ever been found.

The genetic record is profound evidence of the evolution of the Platyus. We no longer need fossils. We can compare genomes. Study, learn, and then criticize

[Southerngl]

Which came first, the chicken or the egg?

(Chicken and egg lying in bed, Chicken smoking a cigarette)

Egg says: Well. I guess we know the answer to THAT question.

[P8riot]

God doesn’t make mistakes. The Platypus and Echidna are just examples of him thumbing his nose at Darwinists.

[CarrotAndStick]

"Not one fossil of a platypus-like (but not a platypus) creature has ever been found."
 

Platypus - Evolution and Conservation

A modern Platypus. Photo: Carl Bento, Australian Museum


Skull of Obdurodon (left) compared with modern Platypus (right) The holes in the upper jaw of Obdurodon are alveoli for true teeth - note the horny pads on the modern Platypus instead of teeth. Photo: Carl Bento, Australian Museum


Opalised jaw fragment of an extinct monotreme, Steropodon galmani, showing teeth. Photo: Carl Bento, Australian Museum

• What are Platypus?
• What do fossils tell us about Platypus?
• What is the evolutionary history of Platypus?
• What are the implications for conservation of Platypus?

Words to know:

• MONOTREMES - the group of mammals that lays eggs.
• MESOZOIC ERA - approximately 245 - 65 million years ago. (The three periods of Triassic, Jurassic and Cretaceous are included in this era).
• GONDWANA - the ancient southern supercontinent that included Australia, New Zealand, New Guinea, South America, Africa, India and Antarctica.

The Platypus (Ornithorhynchus anatinus) is a unique Australian species. Along with echidnas, Platypus are grouped in a separate order of mammals known as monotremes, which are distinguished from all other mammals because they lay eggs.

The fossil record for monotremes is poor in comparison to that of other groups of mammals, and until recently little was known about their evolutionary history. Several fossil discoveries since the early 1970s have shed some light on the origins of monotremes. We now know that monotremes were present in Australia during the Mesozoic Era, when Australia was still part of the supercontinent, Gondwana. The fossil evidence suggests that monotremes originated and diversified in the Australian/Antarctic section of Gondwana, and that there was only a single dispersal to South America before the break up of Gondwana.

Four species related to Platypus have been found in fossil deposits from Australia, including a complete skull of Obdurodon dicksoni and an opalised jaw fragment of Steropodon galmani. The latter is 110 million years old and represents one of Australia's oldest mammals. The only evidence that Platypus ancestors were once present outside Australia came in 1991, when a 61 - 63 million year old fossil tooth was found in Patagonia, in southern Argentina.

Studies of these fossils indicate that the one remaining living species of Platypus is more specialised than its predecessors. It is smaller, its functional teeth have been replaced by horny pads and other aspects of its anatomy appear simpler. It also appears to have a more restricted distribution, being confined to the river systems of eastern Australia. Although Platypus remains widespread and reasonably common, this trend towards increasing specialisation suggests that it may be moving out onto an evolutionary 'limb' and that its current status should not be taken for granted.

Sandy Ingleby
Mammals
Australian Museum
 

 

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