Coelacanths are fish more than two meters long. They are often mistakenly called sea dinosaurs or living fossils (see video below). If their lineage appeared during the Devonian (419 to 358 million years ago), today’s fish are different organisms and have evolved, albeit slowly and with several morphological modifications. It has long been believed that koelakanti disappeared for millions of years until a young naturalist discovered a specimen in a fishing net in 1938. Today, biologists have identified two species: Latimeria chalumnae and Latimeria menadoensis, both very discreet, as observations of these fish in their natural environment, the deep waters of the Mozambique Strait, and especially the Chambers, are extremely rare. Therefore, we know very little about their habits and their biological cycle.
Koelakant knows his sexual maturity at 55 years old
A new study conducted by Ifremer and the National Museum of Natural History has changed the knowledge about the coelacanth: although it is recognized that these fish could live up to 25 years, it turns out that their lifespan is four times higher! That is to say, not far from the century with sexual maturity coming late, around 55 years and a gestation period of 5 years. It was one of the longest in the animal kingdom!
To understand this, researchers, led by Kelig Mahé, from the Ifremer Manche-Mer du Nord haliutic unit in Boulogne-sur-Mer, were able to take advantage of the world’s largest collection of coelacan specimens preserved in the Museum, with 27 fish at all stages of development. They also used new analytical methods, including polarized light, to study their scales, which like tree rings have traces of growth. “Unlike the only previous study dating back to 1977, we used a so-called polarized microscope that allows for finer observation through the play of light and mirrors. And we discovered 5 to 6 additional lines between those already identified in the past. ”, explains Kelig Mahé in a press release.
Coelacant is the slowest fish
The analysis of these labels therefore allowed a reassessment of their lifespan, but also led to even more surprising discoveries that are all the subject of publication in the journal. Current biology. Thus, analysis of two embryos coming directly from the uterus of a pregnant female showed that they were both 5 years old. Using a growth model to recalculate pregnancy length based on offspring size at birth, the researchers obtained the same answer. Therefore, they conclude that the coelacanth is a record holder in the longest period of pregnancy in the animal world!
Embryo Coelacanth. Credits: MNHN.
It also means that “as one might assume, it is indeed a slow-growing and late-breeding species, one of the slowest species in marine fish“highlighted Kelig Mahé. Which is not necessarily good news: species that have a very long and slow life cycle are more susceptible to natural disturbances and to human activity due to a very low replacement rate. However, the IUCN considers two current types of coelactants to be endangered. Scientists now plan to conduct research to determine if the growth of coelacanth is related to temperature. The response will provide insight into the effects of global warming on this vulnerable species.