The coelacanth – an amazing fish believed to have gone extinct alongside the dinosaurs 66 million years ago, before it was unexpectedly found alive in 1938 off the east coast of South Africa – presents new surprises.
In a new study, scientists said that these nocturnal inhabitants of the deep sea have a life expectancy of five times what was previously thought – up to about a century – and that females carry their young for five years, the longest known gestation period. in any animal.
Focusing on one of the two living species of coelacanth, the scientists also determined that it develops and grows at one of the slowest rates of any fish and that it does not reach sexual maturity until about 55 years of age.
The researchers used annual growth rings deposited on fish scales to determine the age of the coelacanth, “just like you read tree rings,” said marine biologist Kélég Mahé of the French oceanographic institution IFREMER and author of the lead study published this week in the journal current biology.
Coelacanths appeared during the Devonian period, about 400 million years ago, about 170 million years before the appearance of the dinosaurs. Based on fossil history, it is believed to have disappeared during the mass extinction that wiped out about three-quarters of Earth’s species after an asteroid impact at the end of the Cretaceous period.
After the coelacanth was found alive, it was listed as a “living fossil,” a description that scientists have now avoided.
“By definition, the fossil is dead, and coelacanths have evolved a lot since the Devonian period,” said biologist and study co-author Marc Herpin of the National Museum of Natural History in Paris.
The fins of the coelacanth are lobe-shaped, which are structurally different from other fish. These fish are believed to have paved the way for limb growth in the evolution of the first terrestrial vertebrates.
Coelacanths live in ocean depths of up to 800 metres. During daylight hours they reside in volcanic caves alone or in small groups. Females are usually larger than males, reaching about two meters in length and weighing around 110 kilograms.
Previous research had suggested it had a life expectancy of around 20 years, with one of the fastest rates of body growth among fish. However, it turns out that this was based on reading errors decades ago with other types of rings deposited on the scale.
“After reassessing the life history of the coelacanth based on our new age estimate, it appears to be one of the slowest – if not the slowest – fish,” said Bruno Ernandi, a marine evolutionary ecologist and co-author of the study. “Life expectancy in centiles is something.”
The Greenland shark, the great predator of the deep ocean, is the longest-lived vertebrate on Earth, with a life expectancy of about 400 years.
