Some snakes have fangs at the front of their mouths, others in the back of their mouths, and some nowhere. It was always quite indistinct how Leiden biologists so come, but now understand it. The gift and appears to be a one-off invention, which has been adopted in the course of evolution, different positions.
Many snakes have fangs, but they look very different, and not always in the same spot in their upper jaw. His arms once emerged in the evolution of several groups snakes they invented independently?
For both positions until now something to say, says biologist Freek Vonk because the snake family tree is a strange jumble, But shows the evolution of snake embryos that it is a single invention. For all fangs evolved from the same piece of tissue, which in the upper jaw, they eventually end up. Snakes can be primarily divided into "modern" types, with fangs and venom glands, and primitive, without poison. As the names indicate, most biologists assumed that the venom glands arose after the split into these two groups. Already in 2005 it turned out that they were wrong. When discovered a group of researchers, including Spark (then a biology student at Leiden) which also feature lots of lizards from venom glands. Their conclusion was that the first venom glands all originated in a common ancestor of snakes and lizards (see 'Toxic Dragons - glands sit a long time in the family, "Northern News, November 17, 2005). That discovery made the columns of Nature.
And now it's hit. Vonk and his colleagues have sliced snake embryos cut to follow the evolution of fangs. They wanted to know how this happens at different snake species. To their surprise, the fangs were found the front slang en bek to have the same origin as fangs sitting in the back. The team, mainly of Leiden researchers, discovered that the teeth and its associated glands at each venomous snake arise from a particular piece of tissue, which behaves differently from the rest of the jaw future.
Vonk: "And those pieces always occur in the same places, at the back of the mouth. But they continue not always. "The most dangerous snakes in the world, cobras, and vipers, this tissue grows into impressive hollow teeth with a muscular Gifreservoir it. "While moving the development of embryo forward, or rather the tissue behind it grow faster so that they stand in the front of the mouth when the tube comes out of its egg."
Embryos from harmless, but technically it poisonous snakes, such as the grass snake, address it differently. With them growing a piece of tissue even in the back of the mouth, but stays there. There's a row of teeth before the fangs, which originate from a different piece of fabric. These teeth are smaller, and Gifreservoirs do not own muscles to press them quickly. That probably looks more like the original situation, says Vonk. The picture is as follows. First, there were snakes probably had venom glands in their upper jaw, only without specialized fangs. That group was about sixty million years ago divided into two: one group gradually lost its toxicity, from the present primitive snakes arose. And a group that remained toxic. That toxic group is then further split fairly quickly.
Vonk: "It is precisely because the embryonic development of the posterior teeth when these houses became disconnected from the rest of the teeth, they were given the opportunity to develop these rear teeth further to fangs useful in all kinds of variations. That was a great success. Of the three thousand species of snakes that are now appearing on earth, is heard in 2700 at home in that group. You can find them almost everywhere, and they owe their sophisticated weapons. "The most dangerous snakes in the world are to see clearly as they distend their mouths, this applies for example to the "inland taipan 'that lives in the desert of Australia. "Even a small scratch of such a tooth can be fatal," says Vonk. A taipan has enough poison with them to kill hundreds of people, he said. But that does not stop him from picking up such a beast as He'm encounters. Spark is, in fact, a decade obsessed with snakes and other reptiles. First, it was a hobby, now also his work. He got in May Top Talent grant from NWO: 180 thousand euros to join doctoral research at their discretion. To poisonous snakes, of course.
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