Featured Image Credit: G. Cooke via AAAS / Science
By: Laura Lillycrop
You may have read stories online about unusual species of fish that can walk and breathe air, showing that these animals may be more capable of adapting to life on land than previously thought.
The evolution of the ancient fish that switched from living in an aquatic environment to living on land about 400 million years ago is one of the most climactic moments in the history of the animal kingdom. These first four-limbed species conclusively gave rise to amphibians, reptiles, birds and mammals.
Photo Credit: kidspressmagazine.com
At the time that fish started moving onto land, the fossil record suggests there was a great deal of diversity among fish. This diversity caused heightened competition between the different species and a big motivation factor for those fish that could make use of opportunities on land.
Those fish that had the flexibility to allow them to move out onto land were able to remove themselves from a very competitive environment and into a new habitat of plants and insects. This new habitat proved advantageous, rewarding them with increased shelter and food resources.
However, new studies show that the first fish to take the leap onto land wasn’t the only one to catch a lucky break. Our marine partners may have evolved the ability to come out of the water at least 30 times over the ages.
This information stems from a new study at University of New South Wales in Kensington, Australia focusing on the diversity of amphibious fish currently alive. Their work places emphasis on the factors that foster extreme lifestyle changes. It may even hold some clues as to how the very first fish took to land.
Terry Ord and Georgina Cooke, scientists working on this study, found 130 fish species that live on land today to some degree.Atlantic mudskipper uses armlike fins to crawl around on mudflats to find food, and the bichir that has lungs for breathing air and stubby fins to pull itself along on land.
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There is also the American eel that crawls between ponds after a rainstorm and long-spined sea scorpion that hops out of tide pools when oxygen levels reach a critical level.
The authors of this study say it’s a safe assume that hopping up on land evolved at least 33 times since this is the number of families that contain at least one fish with an affinity for solid ground.
However, in the process of studying these fish, the two scientists uncovered that two blenny species categorized as “marine” actually spent a large portion of time out of water. If that’s at all representative of the other groups of fish where the scientists found affinity for land, this may be indication that 33 is too low of a guess as to how many times marine dwellers have evolved over time.
Curiously, the transition to land for these critters seems to happen more frequently in intertidal zones. These are areas immersed in water at high tide and exposed at low tide.
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Given that the intertidal zones seem to be a beginning point for moving up onto land for marine species today, it is speculated that it may have been hundreds of millions of years ago for both fish, as well as for our ancestors.
It could be that most of the recent findings in science suggest that human ancestors came from the sea.