In 1878 the German anatomist Karl Gegenbaur theorized the possible evolution of limbs of mammals from branchia of prehistoric fish.
However, in the absence of fossil evidence, his theory was discarded until today, when the implication of the gene has been discovered. Sonic hedgehog, baptized in honor of Sonic the Hedgehog, the famous character of the videogame company SEGA.
This discovery has been carried out thanks to the study of a cartilaginous fish from the family of sharks, showing that we may have to do with them much more than we think.
What is the function of the Sonic gene?
This gene, named after a group of scientists from Harvard video game fans, is known for performing various functions throughout the different stages of vertebrate development, among which are the brain growthHe, the specification of the motor neurons or the development of teeth. However, our role today is related to the formation of extremities, which takes place in several steps throughout the different stages of the embryonic development.
For starters, at the earliest stages of mammal development, set up the shaft of limbSo, for example, in one hand you would select the location in which each of the five fingers has to grow, from thumb to little finger.
Then, in later stages of development, he ensures that the limb grows to its full size.
How do the fins of cartilaginous fish evolve?
To check whether Gegenbaur theories were correct and the limbs of mammals have a common origin with those of fish, these scientists of the University of Cambridge, who have published their results in the magazine Development, have been based on the development of the embryos of a type of stripe, known as skate fish.
Both rays and sharks have skin extensions that protect their gills and that they are supported by cartilaginous structures in form of arc accompanied by appendices finger-shaped called gill rays and, if the German hypothesis were correct, the development of these structures should be mediated by the Sonic gen.
How did you carry out the experiments to find out the function of the Sonic gene in fish?
All the statements we have seen so far started out as simple hypotheses; so, to go further, these researchers chose to block gene function in the different stages of development of the streak embryos, thus checking if their theories are fulfilled.
In this way, they could see that if the blockage occurred in the early stages, the gill rays grow in the wrong placewhereas if it was done later, I know they were in the right place, but they did not grow properly.
Therefore, although the end is different in each species, it seems that the development of the limbs follows a practically the same process. in fish and mammals.
They then evolved the fins and limbs together from the same ancestor or each differentiation program took place separately? It is difficult to give an answer to this question. In fact, the researchers responsible for the study affirm that to be able to do it safely they must rely on fossil remains and, so far, no one has been found to serve them.
Be that as it may, I know that they have been able to find an evolutionary link that shows that Gegenbaur was not at all wrong with his theories and, above all, they have once again provided evidence of the importance of the union of the different branches of science, in this case genetics and paleontology. The union is strength!
Images: Mirror
