Coelacanths, from the Latin for hollow spine, are crossopterygii, a class of bony fishes most members of which are extinct or, at least, thought to be extinct. These fishes are thought to be direct evolutionary ancestors of amphibians and, consequently, of all land living tetrapods[1], living and extinct. Indeed, coelacanths, fossils of which have been found in rocks dating from the Devon through to the end of the Cretaceous periods, i.e. approximately between 380 to 75 million years ago, had long been thought to be extinct ever since they were first described by John Woodward (1665-1728) the English naturalist, antiquarian and geologist. But, surprise, the coelacanth was not actually extinct; in December 1938, a very much alive specimen was found off the River Chalumna, in waters on the east coast of South Africa. Since then, the fish has been found along a long stretch of the east African coast, in Tanzania, Kenya, Mozambique, South Africa, as well as the Indian Ocean islands of Madagascar and the Comoros. Some 60 years after the first living coelacanth was discovered (1998), the scientific world was again stunned with the announcement that yet another species of the fish had been discovered on the other side of the Indian Ocean, in Sulawesi, Manado, Indonesia. The coelacanth is now recognized as one family, Latimeridae[2], one genus, Latimeria, and two species, Latimeria chalumnae, the African species, and Latimeria menadoensis, its Asian cousin.
Coelacanths have some peculiar characteristic that differentiate them from other fishes and animals.
The fish is possessed of fleshy fins. These lobate fins, as they are known, are by no means unique to the coelacanth, but it is the only fish group that has developed seven such fins, the paired fins being supported by girdles that, it is thought, might be the precursors of the pelvic and pectoral girdles found among tetrapods. The fishes are not vertebral creatures, being supported by a hollow tube that is stiffened by fluid under pressure known as a notochord.
The skull of the coelacanth has a unique design that permits the fish to open its mouth by moving not just by moving the lower jaw, but also by moving the upper jaw. This arrangement which permits a considerably increased gape, is unique in the animal world.
The brain of the coelacanth is amongst the smallest in the world, occupying just approximately 1.5 % of the cranial cavity, the rest of the cavity being filled with fat.
The fish is viviparous, i.e. gives birth to its young live, its eggs, the size of chicken eggs, hatching within the females into embryos, which are born in due course. The young fish measures between 35 and 38 centimeters at birth and grows up to 150 centimeters in the male and up to 190 centimeters in the female. Adult fishes weigh in at between 50 to 70 kilograms. The African species is bluish-grey with white marks distributed over the body. These marks are unique to each fish, in the manner of human fingerprints. On dying, the fish turns brown. The coloring of the Asian species is less clear, not enough specimens having come to light, but one live specimen was a brownish color.
The coelacanth has a very narrow habitat range. Combined with its specialized physiology and lifestyle, as well as past overfishing for scientific and pseudo-scientific purposes, the fish is listed in the International Union for Conservation of Nature (IUCN) Red Book as a critically endangered species.
The coelacanth is not a food animal as such, because it’s extremely high oil content gives the flesh a mean and tainted taste, although it was occasionally consumed on account of its presumed anti malarial qualities. A somewhat more bizarre, and more serious from the point of view of coelacanth survival, was the idea that consuming the fluid in the fish’s notochord had a life prolonging effect! This idea contributed to the overfishing of the species, as individual fishes went for several thousand dollars ostensibly for medicinal purposes!
[1] Tetrapods are the class of vertebral animals other than fishes.
[2] Named for Marjorie Courtenay-Latimer (1904-2004), a curator at East London (South Africa), who, failing to identify the fish had sent a sketch to L. B. Smith (1897-1968) an ichthyologist at Rhodes University (South Africa) who identified the fish as a coelacanth.
