Sydney - Australia's early settlers were mystified by the platypus, an animal that looked like nothing else on earth and had the strangest of habits.

A team of international researchers released its genetic blueprint Thursday, and its genes turned out to be as whacky as the animal itself.

"It's really weird," said Sydney University's Kathy Belov. "We still don't know how platypus determine sex. The gene that does it in other mammals doesn't do it in platypus."

Another oddity is that the platypus is born without an immune system but seem to develop one from ingredients in the mother's milk.

The platypus lives the life of a lizard, and like a lizard lays eggs, but it has fur like an otter. It swims like a fish, but runs like a rat and can even growl. The duck-billed creature is shy, almost nocturnal and mostly lives alone.

Along with the echidna, it makes up a group of Australian natives called monotremes, which lay eggs but suckle their young. Though they have a lower body temperature than other mammals, they are mammals all the same.

The male platypus has a claw and a venom duct that used together can kill an opponent and can give a human a nasty wound.

The gene map findings, published in the journal Nature, give a deeper insight into the uniqueness of the platypus.

Australian National University geneticist Jenny Graves said the early settlers were right in thinking that the platypus was a bit of an evolutionary mix up.

When dead specimens were shipped to London, recipients thought it was all a hoax and that the strange creatures had been cobbled together by taxidermists as a practical joke.

The researchers say the platypus is the first animal to have evolved from reptile to mammal and that it retains the characteristics of both. They said the mixture provides clues to the function and evolution of all mammalian genomes.

Belov, whose specialty is the immune system, said molecules in the platypus develop into their own microbials, which are broad-spectrum antibiotics.

"This is big news for science," she said. "We've probably learnt more during this study about platypuses than we have in decades and decades." (dpa)