Strange ‘Walking’ Fish Helps Explain Animal Evolution

A strange African fish capable of “walking” and breathing air may help explain how ancient fish evolved and adapted to land.

Scientists are studying this modern fish, known as the bichir (Polypterus senegalus), in the hopes of understanding how the now-extinct stem tetrapods crawled out of the sea 400 million years ago. The bichir, with lungs for breathing and stubby fins that act as rudimentary legs, have many traits similar to the prehistoric creatures.

In order to learn how the ancient tetrapods may have evolved, researchers experimented with the bichirs. They raised groups of fish on land over an eight-month period to see how they developed in comparison to bichir living in the water. The idea was to see how a land-based environment might change their anatomy and behavior, not unlike the evolutionary challenges their ancestors faced.

Scientists designed a special aquarium that had enough water to keep the fish moist, but was essentially land locked. After researchers compared these fish to the ones raised in water, they made some startling discoveries. The land-raised fish showed significant changes in bone structure and musculature. They were also able to raise their heads higher and pull themselves along or “walk” faster. In effect, they adapted to life on land.

Researchers refer to this adaptability as plasticity. They suspect that plasticity was also common among the bichir’s evolutionary ancestors. Unearthing fossils of stem tetrapods from a sample population would help confirm this theory, said study co-author Hans Larsson. That is unlikely to happen anytime soon, but for now, researchers would like to raise several generations of land-based bichir to see how they continue to “evolve.”

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