Coelacids were long thought to be extinct. Because fossils were found but never living specimens, zoologists were convinced that the animals, up to two meters long, did not survive the great extinction of species around 65 million years ago and disappeared with the dinosaurs. It was a sensation when a coelacanth was caught in the Indian Ocean off the South African coast in 1938 – but it did not survive the operation. To this day, little is known about the strange Comoros coelacanth, which during the day can be found in groups in lava caves about 200 meters below sea level. At night they go hunting for other fish alone and tear their mouths wide open with the help of a special joint in the skull.
Apparently it still happens that apparently certain findings about the animals have to be revised: A study by French researchers that is currently in the specialist journal Current Biology has appeared shows that the primeval fish can live up to 100 years. And not just 20, as was previously thought.
The fish embryo in the womb was already five years old
“The age of the Comoros coelacanth was underestimated by a factor of five,” says Kélig Mahé from the Fisheries Laboratory in Boulogne-sur-mer, France, who led the study. Mahé and his team examined 27 coelacanth exhibits from a collection of the Muséum National d’Histoire Naturelle de Paris. From two-meter-long fully grown specimens to embryos that were still in the uterus, everything was included.
To determine the exact age of the fish, the researchers used a new method with which they could visualize tiny calcified structures on the animals’ scales. Just as the number of rings in the trunk of trees allows conclusions to be drawn about age, these structures can be used to determine the age of the coelacanth, the researchers write in their study.
The oldest of the specimens examined is therefore 84 years old. “Our new assessment of age also enabled us to reassess the rate at which the Comoros coelacanth grew,” says Mahé. Accordingly, the animals grow extremely slowly. The two embryos that were still in the womb, for example, were already five years old, according to the new findings.
“Comoros coelaceans seem to develop extremely slowly compared to other marine fish,” says Mahé. According to the scientists, this does not only affect growth. The animals obviously lead a leisurely, slow life and only become sexually mature at the age of 55, for example. The mothers then carry the offspring for at least five years, as the age determination of the embryos suggests.
With their cozy lifestyle, the Comoros coelacids have something in common with other animals that also live to a great age: the Greenland Shark, for example, which can live to be more than 500 years old. It is not for nothing that the Latin name of this animal, which is known among arctic fishermen for its indolence, is Somniosus microcephalus: “the sleepy one with the small head”.
The sharks live in ice cold water and have a very low body temperature. The metabolic processes in your body therefore run extremely slowly. Greenland sharks are four to five meters long on average, but only grow one centimeter a year. They reach sexual maturity at the proud age of 150 years.