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The blind cavernicolous, pale pink, has been living in darkness for millions of years, which has made it lose its old system of DNA repair.
If you spend an hour in a dark room, you will notice significant changes. Your eyes start to get used to the darkness, your other senses sharpen and you might feel a little weird. Imagine living the rest of your life in darkness – and then your offspring and that of your offspring will do the same thing, for countless generations. Much more would begin to change than your sight.
This is especially noticeable in the case of cave creatures. The cave is a very specific environment, with little or no light and generally constant temperatures. There are more than 200 species of cave fish described scientifically, all of which show specific adaptations to this environment. One of them can teach us something very important about mammals, including ourselves.
Organisms such as bacteria, fungi, plants and even most animals have the ability to capture the energy of visible light to repair DNA damage induced by ultraviolet (UV) light . But placental mammals do not do it. So, all these mammals, including humans, probably come from a creature that has lost that ability – just like this cave fish in Somalia.
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This confirms the theory that the ancestor of mammals had an underground or exclusively nocturnal lifestyle, perhaps as a strategy to avoid being eaten by predators such as dinosaurs.
"We have revealed in a species of blind cave fish the loss of an old, highly conserved DNA repair system," says Nicholas Foulkes of the Karlsruhe Institute of Technology in Germany. "Curiously, the only other animals known to date for which DNA repair by photoreactivation is absent are placental mammals. Thus, what we see in this species of cave fish is perhaps the first step in a process that has already occurred in our ancestors in the Mesozoic era. "
The fish in case, Phreatichthys andruzzii has been living in total darkness for about three million years, far more than other cavity fish that have not yet lost this ability. This gives us a rough idea of how long it takes for this to happen – an important clue to identifying the ancestors of mammals.
"Many features of modern mammals, such as the anatomy and function of the eye, show the characteristics of a nightlife lifestyle," Foulkes explains. "This means that we can now predict with greater confidence that mammal ancestors have experienced a prolonged period of evolution in total darkness."
At present, researchers want to further study the fish and see if it has lost or impaired other abilities using the sun to function properly.
Journal reference: Current biology, Zhao et al.: "Modulation of DNA repair systems in blind caverniculturists during evolution in constant darkness"
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