African coelactants are very old. Fossil evidence dates back about 400 million years, and scientists thought they became extinct until 1938, when the museum’s curator Marjorie Courtenay-Latimer noticed mercury in a fishing net.
Found on the southeast coast of Africa, coolant they also live long – scientists doubted about 50 years. But proving that life expectancy was hard. (Coelactants are endangered and accustomed to deep water, so scientists can’t just shove their babies into a tank and run a timer.) A French research team that examined their scales with polarized light found they could probably live much, much longer. “We were taken aback,” says Bruno Hernande, the marine ecologist who led the study. The new estimated lifespan, he says, “was almost a lifetime.”
His team from the French Institute for Marine Exploitation, or IFREMER, found not only that individuals can live to be nearly 100 years old, but also that they have gestational periods of at least five years and cannot sexually mature until they turn at least 40. Results were released on Thursday at Current Biology. This slow-moving life underscores the importance of efforts to conserve this rare species, which has been labeled “critically endangered”. IUCN Red List. Only about 1,000 exist in the wild, and their long pregnancies and late maturity are bad news for the resilience of their population to human attacks. “It’s even more endangered than we thought before,” says Hernande.
“This will have huge consequences,” agrees Daniel Pauly, an ichthyologist at the University of British Columbia who was not involved in the study. Pauly is the creator of FishBase, a database of biological and ecological information on tens of thousands of species. If a fish takes a decade to spawn, killing it destroys its potential for population recovery. “A fish that needs 50 years to mature, as opposed to 10 years, is five times more likely to be in trouble,” he says.
Koelakanti are thick scales that grow up to two inches, and for decades ichthyologists have been debating how to read those scales in search of signs of age. In the 1970s, researchers noticed small calcified structures on them. They thought the rings were signs of age, like rings on a tree. However, they disagreed on how to count them: Some concluded that each label signifies one year; others believed that seasonal turns create two rings a year. At the time, they best assumed that their life expectancy was about 22 years. That conclusion, which meant the 200-pound stake weighed 17 years, implied they were growing very fast: “They would grow as fast as tuna, which is crazy,” Pauly says.
It is crazy because these are animals with a slow metabolism, which should indicate slow growth. Coelacanth’s hemoglobin is adapted to a slow metabolism, which means that they cannot take in enough oxygen to support fast-growing fish. Some claim that their small gills are additional evidence of oxygen restriction. They also live a very passive lifestyle, resting most days in caves and slowly scurrying through twilight zone of the ocean, down to 650 feet and below, when they are worthy to move. “Predominant, biological traits point to slow-living fish,” says Hernande.
In addition, scientists who follow the lives of individual coelacanths knew that 20 years was far too little. In the eighties, researchers began sending submarines and remote-controlled vehicles to the cave where there are 300 to 400 koelakanta. They returned to this place for more than 20 years. During each visit, they recognized individuals by their characteristic white markings. Only about three or four fish in this group would die, and an equal number of new ones would be born each year. This observation provided astonishing evidence that coelacants live long – even more than 100 years, that study claims.