Clogged growth rings in coelacanth scales indicate that the fish can live not 20 years, but nearly 100 years, according to the researchers.
Almost everything about coelacanths – a fish with fins that seem to stand still – indicates a “slow life”. However, using growth rings in the scales, the researchers concluded that the giant fish did not live more than 20 years. Not slow growth, but very fast growth.
A particular contradiction, according to French marine ecologists. So they re-examined the fish. The team discovered more growth rings, visible only under polarized light. Conclusion: Coelacanths likely lived five times longer than previous researchers suggested, ecologists write in the journal current biology – Maybe almost a century.
coelacanths, such as the African coelacanth (Latimeria Chalumni) Its length can reach two meters. They have a slow metabolism and absorb oxygen from the water relatively slowly. Coelacanths also breed eggs: the eggs are incubated in the mother’s body. All these qualities are typical of slow growers, who can age.
However, two previous studies (from 1939 to 2000) on the age and growth of fish found the opposite. Growth rings (circles) on the scales, which are comparable to tree growth rings, indicate that coelacanths are fast growers. They will live for a maximum of 20 years.
The team behind the new study took the scales of 27 African coelacanths (Latimeria Chalumni), which was captured between 1953 and 1991 off the coast of the Comoros Islands, is under examination. And they found that the circuits their colleagues described earlier weren’t the only ones. For each episode, they found, on average, five smaller streaks – visible only under polarized light.
Additional ‘broken’ circles indicate that the estimated lifespan of coelacanths has been underestimated by the authors of previous studies by fivefold. Fish can live no more than 20, but even 100 years. According to the researchers, the oldest of the 27 coelacanths was 84 years old.
Incidentally, there have been several studies that suggest – in part on the basis of their typical “slow lifestyle” – that coelacanths live well beyond 20 years maximum. The age of perhaps 100 has not been estimated before. Coelacanths are difficult to hunt because the fish are highly endangered and thus rare. So scientists usually have to make do with “museum specimens” that are already dead.
Using the new estimated age, the researchers estimate that males are sexually mature (read: fertile) between 40 and 69 years, and females between 58 and 66. Also, circles on the scales of two fetuses indicate that females may be up to five years pregnant.
Christian Tudorach, a biologist and fish physiologist (Leiden University) who is not involved in the research, is not convinced of the latter. “I don’t find late sexual maturity strange. We see it a lot. Pregnancy (read: gestational age, red.) for five years, on the other hand, I find unlikely. Five years of pregnancy versus a 30-year fertile period (between 40 and ~70 years, red.It doesn’t seem worth it in any way from a biological point of view.”
“A five-year gestation period is not worth it from a biological point of view”
Christian Tudorach, biologist and fish physiologist (Leiden University)
Although Tudorache talks about a nice new way to determine the age of fish, the biologist is critical. “I miss the verification process using a well-known method like ear dust analysis. That would make the research and conclusions much stronger.” Ear stones, also called hearing stones, are structures in the inner ear of fish. The age of the fish can be determined by the annual growth rings in the ear dust.
The biologist agrees that coelacanths are special animals, and are still quite a mystery, so it’s a good idea to do research. However, the “frequent fanfare” about fish has been found to be somewhat exaggerated. “Century is a long time, of course, but coelacanths are by no means the only saltwater fish. In this way, the belugaster (spindle spindle) live 150 years ago and a few years ago a Greenland shark (Somniosus microcephalyDiscover – a real living fossil – over 500 years old.”
Bild: Laurent Ballista; Bruce Henderson/CC BY-SA 4.0; Mahe, Hernande and Herbin, 2021 / Current Biology