CAPE TOWN: The coelacanth — a wondrous fish that was thought to have gone extinct 66 million years ago before unexpectedly being found alive and well in 1938 off South Africa’s east coast — is offering up even more surprises.
Scientists said a new study of these large and nocturnal deep-sea denizens shows that they boast a lifespan about five times longer than previously believed — roughly a century — and that the females carry their young for five years, the longest-known gestation period of any animal.
Focusing on one of the two living species of coelacanth, the scientists determined that it develops and grows at among the slowest pace of any fish and does not reach sexual maturity until about age 55.
The researchers used annual growth rings deposited on the fish’s scales to determine the age of individual coelacanths — “just as one reads tree rings”, said marine biologist Kelig Mahe of the French oceanographic institution Ifremer, who is lead author of the study published last week in the journal Current Biology.
Coelacanths first appeared during the Devonian Period roughly 400 million years ago, about 170 million years before the dinosaurs. They were thought to have vanished during the mass extinction that wiped out about three-quarters of Earth’s species following an asteroid strike at the end of the Cretaceous Period.
After being found alive, the coelacanth was dubbed a “living fossil”, a description now shunned by scientists. “By definition, a fossil is dead, and the coelacanths have evolved a lot since the Devonian,” said biologist and study co-author Marc Herbin of the National Museum of Natural History in Paris.
It is called a lobe-finned fish based on the shape of its fins, which are thought to have paved the way for the limbs of the first land vertebrates to evolve.
Coelacanths reside at depths of as much as 800m. During daylight hours, they stay in volcanic caves alone or in small groups. Females are somewhat larger than males, reaching about 2m long and weighing 110kg. Previous research had suggested roughly a 20-year lifespan and among the fastest body growth of any fish. It turns out that this was based on a misreading decades ago of another type of ring deposited in the scales — Reuters
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