ON DECEMBER March 23, 1938 Marjorie Courtenay-Latimer, curator at the East London Museum, South Africa, stumbled upon her local fish market. There, she spotted the most beautiful fish she had ever seen. It was pale mauve, was nearly two meters long, and had silver markings. Although she had no idea at the time, it turned out that he was part of a group called the coelacanths, which until now were believed to have gone extinct along with the dinosaurs.
This find, called Latimeria chalumnae in honor of Courtenay-Latimer, showed that coelacanths are still very much alive. It has been hailed as the most important zoological discovery of the century. Now the work that has just been published in Current biology by Kélig Mahé of the Fisheries Laboratory, Boulogne, France, suggests that in addition to having lasted collectively for over 400 million years, coelacanths also hang around as individuals for a long time. Dr. Mahé’s study indicates that they have a lifespan similar to that of human beings, which places them among the vertebrates with the longest lifespan in the world.
The excitement at LatimeriaThe discovery of s was not only due to the curiosity of his survival. It is also that the coelacanths belong to a group that has lobe-shaped fins of a kind that are believed to have been precursors to the members of terrestrial tetrapods. Many experts have therefore sought to study Latimeria closer. It is, however, difficult. Latimeria is solitary, nocturnal, lives at depths less than 100 meters, and is known only from the southwest Indian Ocean and from a second, smaller population, L. menadoensis, near Manado Tua, an island in Indonesia.
In particular, Dr Mahé wanted to know how long Latimeria Lives. Previous work, which examined the annual growth rings in its scales, suggested a maximum of 20 years. This does not correspond to the animal’s slow metabolism and low fertility, two characteristics characteristic of long-lived species.
Rather than using standard microscopes, he and his colleagues used polarized light to study the scales. This revealed additional growth rings so thin that previous work had missed them. Of the 27 people studied, six were in their sixties and one was 84 years old.
It was a discovery that Dr. Mahé and his colleagues had expected more than halfway. What really surprised them was a discovery made while looking at two unborn youngsters – for Latimeria Females bear live young rather than laying eggs. The scales of the fetuses suggested they were five years old, a remarkably long gestation period given the previous record of three-and-a-half-year-old vertebrates held by the deep-sea frilled shark.
While interesting in some ways, Dr. Mahé’s discovery is bad news. An already rare, slow-growing animal with a gestation period of half a decade has about the most extinction-prone profile imaginable. Latimeria is protected by law, insofar as this protection concerns the sea, and is not a particular target for fishermen. But it is already listed as Critically Endangered by the International Union for the Conservation of Nature. It would be both ironic and tragic if, after surviving the impact of asteroids 66 million years ago that struck dinosaurs, coelacanths were to disappear for good under mankind’s watch. ■
This article appeared in the Science & Technology section of the print edition under the title “More curious and more curious”