[Animals] The platypus is one of the strangest creatures on earth. It lays eggs like birds and produces milk like mammals

[SnO]

The duck-billed platypus is the strangest mammal on Earth. It has a host of strange characteristics. It lays eggs like birds instead of giving birth, and produces milk like a mammal, but through its skin. It also has a beak like a duck, fluorescent fur, a tail like a beaver, two poisonous spines on the male's hind feet, and 10 sex chromosomes.

 

 

The platypus belongs to the order Monotremata, which existed millions of years ago, even before any known mammals appeared today. However, these strange characteristics have made this animal - which inhabits the eastern coasts of Australia - a subject of interest to scientists since its discovery in the late 18th century.

Complete genetic map
Recently, a team of scientists at the University of Copenhagen, Denmark, conducted an extensive genetic survey of this strange animal, hoping to find out the secret of its strange features, as scientists managed in this recent study published in the journal "Nature" on January 6. This January managed to map the complete genome of the platypus.

"The complete genome map of the platypus provided answers as to how the platypus acquired some of these strange traits," said Joji Chan, professor of evolutionary biology and lead researcher of the study.

"Of course, knowing the platypus' genetic code is important, because it explains why we and other mammals are such creatures that give birth to young rather than lay eggs."

Platypus is a mixture of mammals, birds and reptiles (Getty Images)
It lays eggs and nurses its young
Mammals are divided into 3 main orders, monotremes with one pathway for urination, defecation and sexual reproduction, marsupials, and placentals to which we humans belong. The last two groups fall under the class of primary savages that give birth to their young.

However, the monotremes - to which the platypus belongs - differ from both groups, as the platypus is considered a mixture of mammals, birds and reptiles genetically, because it "has retained many of its ancestral traits, which may have been the reason for its ability to adapt to the environment." Where he lives, says Chan.

 

Although the platypus lays eggs, it has mammary glands that sweat milk through the skin to feed its young. Scientists do not know exactly when these three orders of mammals began to differentiate from each other. While some of them see that monotropics were the first to differentiate, others see that the three groups diverged at about the same time.

Shape of the platypus' nest where it lays eggs (Wikipedia - Matteo Di Stefano/Science Museum, Italy)
Genes acquired and lost
It is known that chickens contain the three vitellogenin genes that are important for the production of the egg yolk (yolk), which are the same genes that humans lack. The study showed that the platypus still had one of these genes and therefore laid eggs thanks to this gene, but lost the other two genes approximately 130 million years ago.

And while all mammals had the vitellogenin genes replaced by casein genes responsible for the production of the protein casein, the main component of milk, the platypus had casein genes as well, so its glands secreted milk just as other mammals do.

Unlike the vast majority of mammals, the platypus has two toothless beak plates that it uses to chew food, which is another distinguishing feature. The study showed that the platypus lost its teeth approximately 120 million years ago, when 4 of the 8 genes responsible for tooth development were missing.

 

The platypus has two plated beaks and no teeth (Wikipedia – Twinings)
And while humans possess two chromosomes responsible for determining sex, namely the "X" chromosome (X) and "Y" (Y), as the "X" chromosomes meet in the female (XX), while the male possesses the "X and Y" chromosomes (XY). . The platypus has 10 sex chromosomes, 5 of the "X" chromosome and 5 of the "Y" chromosome, and is thus the only animal that contains 10 sex chromosomes.

By comparing the platypus' sex chromosomes with those of humans, lizards, the Tasmanian devil and the marsupial mouse, the scientists found that its sex chromosomes are more closely related to birds than to humans.

 

https://www.aljazeera.net/science/2021/1/12/خلد-الماء-من-أغرب-كائنات-الأرض-يجمع