Qhen chickens have teeth… Each of us knows the expression. Finally every French speaker. The English language, on the other hand, has chosen to honor another animal. When pigs fly, she says. The prospect of pigs flying is just as impossible, of course. Although… If most mammals remain confined to the cow’s floor, the ability to fly, or rather to glide, has appeared several times in this class of vertebrates – to which, let us remember, we belong. We think of bats, experts in active flight. But other mammals, such as flying squirrels, colugos and three species of marsupials, glide with dexterity.
It is in the latter that a team of American researchers was particularly interested in order to understand how the patagium could have appeared, this membrane which stretches between the legs and the sides, giving them their famous superpower. Why them and not one of the 1,400 species of bats? ” For two reasonsexplains Ricardo Mallarino, lecturer at Princeton University and coordinator of a study published on April 24 in the journal Nature. On the one hand because the patagium appeared independently in these three close species, which allows us to make comparisons. And on the other hand because this membrane develops not in the uterus but in the maternal pouch, therefore accessible to the experiment. » Let us remember that marsupials, including large kangaroos, give birth to larvae weighing around 1 gram… which crawl to the ventral pouch, attach themselves to a nipple and complete their development there.
The team first sequenced the genome of these three species but also of eleven other species of marsupials lacking the famous membrane. She did not find gene mutations capable of explaining the phenomenon. On the other hand, in the three gliding species, she observed accelerated evolution near the gene Emx2. Different modifications, witnesses of a singular history specific to each species, but all located in the same region.
A breeding of sugar gliders
This gene is not unknown to anyone who studies the establishment of large anatomical structures in the embryo. Present in all mammals, it is notably involved in the development of the brain and the pelvic girdle. Could it be that it also played a major role in the growth of the patagium?
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