Fish that learned how to walk
Baku, December 15 (AZERTAC). FiIt has long been believed that all animals on earth, including mammals, amphibians, reptiles, and birds, evolved from fish that eventually developed the ability to breathe, then walk on land, such lungfish, which are still found in Africa, South America and Australia today. As proof of this theory, scientists have now discovered that an African lungfish (Protopterus annectens) with an eel-like body and a pair of flimsy hind fins can lift its body clear off the floor and propel itself forward using scrawny "limbs," abilities previously thought to have originated in early tetrapods (four-limbed animals). "This shows us (pardon the pun) the steps that are involved in the origin of walking," commented researcher Neil Shubin at the University of Chicago. "What we`re seeing in lungfish is a very nice example of how bottom-walking in fish living in water can easily come about in a very tetrapod-like pattern." "If you showed me the skeleton of this creature and asked me to make a bet on whether it walks or not, I would have bet it couldn`t," Shubin said. "Their fins seem like the furthest thing from walking appendages possible." Additionally, while the fish`s forelimbs appear similar to the hind limbs, they are not employed in its walking movements, raising an interesting question as to why? One theory is that the “lungfish`s ability to support its body on its slim limbs might be aided by their buoyant air-filled lungs.” "It shows what`s possible in an aquatic medium where you don`t have to support yourself with gravity," Shubin said. This discovery might redraw the evolutionary route scientists think life took from water to land. Many of the steps needed to adapt to surface-dwelling could have occurred millions of years before early tetrapods developed limbs with digits and took their first steps on shore, added Heather King, an evolutionary biologist at the University of Chicago, “These findings might also make us rethink whether recently discovered (approximately) 380 million year old tracks were in fact made by early tetrapods. They could have been created by other kinds of fish instead,” she wrote in an e-mailtoLiveScience.
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