Fish that can walk on land and breathe air exist, and they're providing important clues to how their ancient ancestors evolved from swimming in the sea to living on land.
In a study published in the journal Nature, researchers at McGill University studied Polypterus senegalus (the Senegal bichir or "dinosaur eel"), fish with "functional lungs and strong fins" that can pull themselves out of the water.
The scientists raised 111 juvenile bichir on land for eight months and monitored changes compared to a control group of fish remaining in water.
"Fish raised on land walk with a more effective gait," lead author Emily Standen told The Verge. "They plant their legs closer to the body’s midline, they lift their heads higher, and they slip less during that walking cycle."
Scientists found major differences between land-raised and aquatic-raised bichir, NBC News reports:
"They found that the land-raised fish lifted their heads higher, held their fins closer to their bodies, took faster steps, undulated their tails less frequently and had fins that slipped less often than bichir raised in water. The land-raised fish also underwent changes in their skeletons and musculature that probably paved the way for their changes in behavior. All in all, these alterations helped bichir move more effectively on land."
So, what does it all mean for the study of evolution?
"This is the first example we know of that demonstrates developmental plasticity may have facilitated a large-scale evolutionary transition," Hans Larsson of McGill University said in a statement, "by first accessing new anatomies and behaviours that could later be genetically fixed by natural selection."
For more, learn how another species of fish also evolved a unique method for getting a meal:
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