Following Napoleon Bonaparte’s incursion into Egypt in 1798-1799, French naturalist Étienne Geoffroy Saint-Hilaire came across a weird fish. It had a pair of lungs and was able to walk on its sturdy fins. In 1802 he dubbed it Polyptere bichir and it was this very fish that helped propel his career as a leading anatomist and one of the earliest evolutionary-development researchers. That fish has a smaller cousin called Polypterus senegalus (bichir) and its terrestrial ambition made it the star of a recent study.
Researchers from the University of Ottawa and the McGill University raised more than a hundred two-month-old bichirs in moist environments for eight months. They purposefully created stressful conditions in order to study their adaptability to this terrestrial habitat. Keep in mind that stressful conditions for fish don’t necessarily have the negative impact as they do on us humans.
In fact, what the researchers learned mirrored what fossil records from the Devonian period, when aquatic animals first started to set foot (fin?) on land, some 400 million years ago.
After eight months, the fish had learned how to walk more effectively. They keep their fins closer to the body and their heads higher off the ground. They don’t slip as often as their aquarium-raised peers. They also took faster steps and their tails undulated less. The researchers had predicted that the fish would develop these abilities in order to survive.
More intriguing, however, is the fact that the bichirs suffered morphological changes. Bones from the neck and shoulder regions changed in order to increase the fin mobility and its independence of motion relative to the neck. This phenomenon is a common biological occurrence called developmental plasticity and it could be responsible for the first fish-powered land venture almost half a billion years ago.
The need for variation led to the development of specialized fins that later evolved into supportive limbs and terrestrial locomotion. Those ancient fish paved the way for the earliest four-legged vertebrates that comprised the first members of the superclass Tetrapoda ( fancy ancient Greek for “four-legs”).
You can have a look at the little critters doing their walk below: