Fish can walk on land. Yes, that’s right, you didn’t misread it – those gill-bearing, aquatic animals can survive on the same surface that terrestrial animals have occupied for the last few millions of years. Oh, and not to mention humans for the last 200,000 years or so!
Fossil evidence suggests that around 400-500 million years ago fish made the grand journey from living in the sea to venturing over land. There is a lot of research dedicated to understanding this transition – with amphibious fish evolving to be able to spend time away from the murky depths of ponds, lakes and seas. Strong muscular limbs and the ability to breathe in air (through the evolution of lungs, co-existing with gills) has enabled fish to survive on land with mudskippers, Mangrove rivulus and lungfish being notable examples.
So how did fish come to walk? It’s one thing existing on land but to walk on it is another matter altogether! Well, when evolution led to fish trading water for land, it is believed that the lobe-finned fishes evolved into the first four-limbed animals, known as stem tetrapods (which ultimately led to the evolution of amphibians, reptiles, birds and mammals). From the fossil records, it is believed that there was great diversity and competition among fish, and so a switch to a land-based life was necessary. But how this transition actually happened is largely a mystery…. until recently. An interesting study conducted by researchers in Canada have plumbed the depths of nature’s mysteries.
Researchers at (the suitably named) McGill University and Ottawa University studied a species of freshwater fish known as bichir (Polypterus senegalus). Bichir possess similar traits those seen in the fossils of the stem tetrapods, such as the possession of primordial lungs and the ability to breathe. The experiment involved taking bichir fish and raising them on land (as well as a control group in water), to test how life on land might trigger changes in such fish.Publishing their findings in the prestigious journal Nature, they deduced that over time, generations of the fish raised on land underwent changes in their skeleton and muscles that allowed them to lift their heads higher, hold their fins closer to their bodies, take faster steps, undulate their tails less frequently, and evolve fins that slipped less often than bichir raised in water
So although it is a stretch to say fish can ‘walk’ as you and I might think it, it is fair to say that the bichir fish (from the experiment) can walk in their own fishy way! And who knows, they may even evolve to do other un-fish like things – a dancing fish would be a sight to behold!
Answer By Chloe Westley