Scientists have found the coelacanth, a huge living fossil fish that was once thought to be extinct, to have the remnants of a lung in its gut.
The coelacanth was thought to be an extinct species until one was found in the deep seas. Since then it has always remained quite a mysterious sea creature that has continued to surprise mankind. Now the latest evidence is in that this fascinating fish has an out-of-order lung in its stomach.
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The rudimentary lung must have functioned once upon a time when the fish was still extant on land. But as it shifted its terrain from the terrestrial areas to the deep seas, the lung became obsolete.
All coelacanths found today employ their gills to extract oxygen from the seawater. However, millions of years ago, the prototypical coelacanths used lungs while living on the land instead of in the sea.
But by the time the Mesozoic Era arrived, the coelacanths invaded the deep sea environment which for obvious reasons was not conducive to lung function. So the lung became a useless organ like the vermiform appendix is in man today.
The coelacanth probably avoided total extinction so many years ago thanks to its entry into shallow waters. While the rest of the dinosaurs died off, this particularly strange creature made the amphibious leap and ended up surviving despite the odds.
Right lateral views of the specimens showing the allometric growth of the lung.
Exactly 66 million years ago all dinosaurs that were not birds were wiped off the face of the earth. But the coelacanth managed to live on and low and behold it is extant even today! Fossils of the coelacanth date back to 400 million years ago in the misty past.
When the first live coelacanth was brought up from the depths of the ocean off the coast of South Africa in 1938, it was termed the Lazarus fish. It was almost like the fish had been literally brought back from the dead. However, the coelacanth still remains an endangered species.
The obsolete lung is larger in the embryos of the coelacanth than in its adult versions. Thus this shows that the lung seems to have lost its function and reason for existence as the animal evolved. As the fish matures, its lung also atrophies.
Among some of the other interesting features of the coelacanth are its lobed fins. They resemble the appendages of a four-limbed animal albeit in vestigial form.
The adult coelacanths found in the wild marine environment today grow to be two meters in length, weigh close to a hundred kilograms and have life spans of 60 years or more. There is still a lot we need to find out about this marvelous fish of the deep.
This study was published in Nature Communications.
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