Coelacanth, a living fossil
There were Coelacanths swimming around in the oceans in 400 million years ago. We only knew them as fossils. And then, in 1938, a fisherman brought up a living Coelacanth.
There were Coelacanths swimming around in the oceans in the Devonian period. That was over 400 million years ago. Research on fossil Coelacanths shows that the genus changed very little over time. The majority of Coelacanth species lived 140 million years later, during the Triassic period. They all died out 65 million years ago, at the end of the Cretaceous, the time of the mass extinction of the dinosaurs. At least …. that’s what everybody thought.
And then, in 1938, a fisherman in South Africa suddenly brought up a living Coelacanth.
The strange fish was taken to Miss Courtenay Latimer, a curator at the East London Museum in South Africa. She couldn’t identify it but sent a sketch with a rough description to a fish specialist. There was huge excitement and telexes rattled out the news all over the world. A fossil fish was back from the dead! A creature that everyone had thought long extinct was still alive and flipping!
After the first Coelacanth was caught in South Africa in 1938, nothing else happened for quite a long time. It was another 14 years before researchers working on the Comoro Islands discovered more Coelacanths. Since then, increasing interest and greater research funding have resulted in the identification of 25 more fish at two places in South Africa alone. New Coelacanth discoveries are expected in the Indian Ocean. Despite this fact, the species has been placed on the list of endangered species, as a precaution against public enthusiasm.
Coelacanths swim very slowly and tend to hang out in a small area. It’s only if they see prey or feel threatened that they swim like other fish. Then, they accelerate by making vigorous movements of their tail and body. The first dorsal fin can be raised or lowered like a fan to keep the fish in balance in the water.
The pectoral and pelvic fins are extremely mobile; as well as moving forwards and backwards, they can also rotate on their axis. Even though the paired fins can move independently of each other like the limbs of four-legged land animals, Coelacanths have never been seen to use them to propel themselves over the sea bed. One very strange piece of Coelacanth behaviour is the way they stand on their heads. A fish will tilt its snout down towards the sea bed and appear to stand upside down for several seconds. Nobody knows quite why they do this. It may have something to do with the operation of an electrosensory organ located directly beneath the top lip. Some people think this is how the fish detects its prey and other Coelacanths.
Coelacanths don’t lay eggs
Most female fish produce eggs and release them into the water, thousands – or even hundreds of thousands – at a time. The currents in the sea can then disperse them over great distances. Coelacanth reproduction is different. The eggs are not released into the water. Instead, they stay inside the mother’s body until they hatch and the young are born alive. This means that the young fish grow up close to their mothers. And that makes it very difficult for the Coelacanth to expand its geographical range.
Nature conservationists sound the alarm as soon as numbers of a species start to decline over an extended period. In the case of most species, we don’t really know how big the population is. And there are some species that have had only small populations for tens of thousands of years and still haven’t died out. A good example is the Galapagos Cormorant. For centuries, there have been no more than 1000 of them on a couple of islands in the Pacific Ocean. They have always survived perfectly well, but recently they have started to need help. The same is true of the Coelacanth, because its very discovery and the public interest surrounding it could be enough to finish off such a rare fish.
After all, similar circumstances proved fatal to the Dodo, a few hundred of which survived on the small island of Mauritius until the 17th century: unfortunately, there was no way of protecting endangered species when it met its end.
Coelacanths are close relatives of the lungfish. Lungfish migrated to dry land 350 million years ago and all land vertebrates are descended from them. That includes amphibians, reptiles, birds, mammals – and us.
If a species is very like one that has been extinct for a long time, we call it a living fossil. Such species are extraordinary both because they have managed to survive for so long and because they have no living relatives. That is why sharks, for example, are not living fossils.
Today’s Coelacanth occupies the same habitat as 65 million years ago and, like its environment, has scarcely changed in all that time. Even so, the modern species is not precisely the same as its prehistoric ancestor. See if you can spot the differences…