The Strange Biology of the Fish That Lives for a Century

Nothing lasts forever.

It's common knowledge that most humans live longer than fish, and many believed one species of which, called the coelacanth, had a lifespan of roughly 20 years. But a new analysis revealed that the creature is really a centenarian of the seas, living up to 100 years, like deep-sea sharks, according to a recent study published in the journal Current Biology.

And, its aging process could be linked to climate change.

The maximum lifespan of the coelacanth is 'five times longer' than thought

The scientists investigated marks on the scales of museum specimens, not unlike evaluating tree rings to determine the age of trees. The research team thinks the centenarian fish reproduces only in late middle-age, and upon inspecting two embryos, the team found both to be roughly five years old. You read that right: coelacanth embryos can live to be five years old before they are born. "Coelacanth appears to have one of, if not the slowest life histories among marine fish, and close to those of deep-sea sharks and roughies," said Kélig Mahé, a scientist with IFREMER Channel and North Sea Fisheries Research Unit in Boulogne-sur-mer, in France, according to a statement in an embargoed release shared with IE.

And this slow-aging process is common in other long-living creatures. "Long-lived species characterized by slow life history and relatively low fecundity are known to be extremely vulnerable to perturbations of a natural or anthropic nature due to their very low replacement rate," explained Mahé, in the release. One reason humans age has to do with DNA replication. Telomeres are "caps" at the end of every strand of DNA that protect our chromosomes, not unlike bottle caps or the plastic tips on shoelaces' ends, and they're a vital part of human cells. Much like shoelaces, without this "cap," the DNA strands accrue damage and reduce the effectiveness of cells.

Every time a human cell copies itself, the telomeres deplete. So naturally, one idea of prolonging or extending life involves slowing the decay of our telomeres, and thus reducing the rate of decay for our DNA. The recent study didn't investigate coelacanth DNA, instead concerning itself with external evidence of age, analyzing the circuli on the creatures' scales. "We demonstrated that these circuli were actually annual growth marks, whereas the previously observed macro-circuli were not," said Mahé. "It meant that the maximum longevity of coelacanth was five times longer than previously thought, hence around a century." But it stands to reason that an underlying biological factor in the unusually long lifespan of the creatures could involve its telomeres.

The coelacanth species' aging process might be affected by climate change

For now, the researchers emphasized the acute implications of their findings on conservation efforts for the coelacanth. According to the researchers, the African coelacanth is regarded as critically endangered, on the IUCN's Red List of Threatened Species. "Long-lived species characterized by slow life history and relatively low fecundity are known to be extremely vulnerable to perturbations of a natural or anthropic nature due to their very low replacement rate," said Mahé in the release. "Our results thus suggest it may be even more threatened than expected due to its peculiar life history."

"Consequently, these new pieces of information on coelacanths' biology and life history are essential to the conservation and management of this species," added Mahé. And a microchemical analysis of the creatures' scales might reveal a relationship between its slowed growth and temperature, potentially shedding light on environmental factors in the aging process affecting this and other vulnerable species in a time of accelerating climate change.