Coelacanth - astonishing find The first
The coelacanth (Latimeria chalumnae) is the only living representative of an ancient order of fishes, until recently thought to have become extinct 70 million years ago, at about the same time as the dinosaurs. In 1938, however, scientists were astonished when living coelacanths were discovered (this is described later).
The coelacanth is a sarcoptergian, or lobe-finned fish, distantly related to the lungfish. However, unlike other bony fishes, the pectoral and pelvic fins of the coelacanth are muscular, and even leg-like in appearance. (The evolutionary ancestor of amphibians, and thus of all land-dwelling animals, had fins similar to those of the coelacanth.) The fins are able to move over 180°, allowing the fish to swim forwards, backwards, and even upside down. While swimming, the coelacanth moves its fins like a quadrupedal land animal moves its legs while walking: the front left and right rear fins move in unison, and the front right and left rear do the same.
The bluish body of the coelacanth is covered with thick scales that are unique to the order. Its jaws are strong. A few specimens have been found with lantern-fish in their stomach, indicating that the coelacanth is predatory in its feeding habits. The retina of its eyes has a reflective layer (similar to that of cats) that helps it see in dimly lit waters.
Most of what we know about coelacanths has come from the study of dead specimens. Some of the first females to be dissected were found to contain several baseball-sized eggs that lacked a shell or hard case. Although it had been hypothesized that fossil coelacanths bore their young alive, this was not conclusively demonstrated until 1975, when a female specimen at the American Museum of Natural History was dissected and five perfectly shaped fetuses were discovered. Each was about 14 in (35 cm) long, and had a yolk sac attached to its stomach. This demonstrated that the coelacanth is ovoviviparous, meaning the female keeps the eggs inside her body to protect them as they develop to the hatchling stage.
Little is known about the ecology of the coelacanth. In 1987, marine biologist Hans Fricke managed to film coelacanths in their deep-water environment off the Comoros Islands in the Indian Ocean. Not only did his team observe the unusual swimming gait described above, but they also saw coelacanths doing "headstands" when the researchers triggered an electronic lure. The coelacanth has an organ between its nostrils called the rostral organ, which is believed to detect the electrical field of prey, as the ampullae of Lorenzini do in sharks. Fricke's research strengthened the evidence that the rostral organ of coelacanths is an electrical sensor.
astonishing find The first
A living coelacanth first came to the attention of science in 1938. At the time, a young biologist named Majorie Courteney-Latimer was the curator of a small natural history museum in South Africa. Because the museum was new, she had been given freedom to decide the direction its collections would take, and she chose to focus on marine life. Local fishermen often brought her unusual fish from their catches. One day, Capt. Hendrik Goosen contacted Courteney-Latimer, saying he had several fish she might be interested in. When she got to the dock, there was a pile of sharks waiting for her. But buried in the pile was a blue fish unlike any she'd ever seen. This one she took back with her to the museum.
The specimen was large, nearly 5 ft (1.5 m) in length, and far too big to fit into the museum's freezer. Desperate to preserve the fish against the hot South African weather, Courteney-Latimer asked a local hospital if she could keep it in their morgue, but was refused. Finally, she managed to get it to a taxidermist.
Knowing that the strange fish was unique, Courteney-Latimer wrote to L.B.J. Smith, an expert on South African fish. Smith recognized the fish as a coelacanth from a sketch provided by Courteney-Latimer. He was able to learn a great deal from the mounted specimen (he dissected one side of it). He then published a notice in the prestigious journal Nature, which announced to the world that coelacanths still existed.
This notice also gave Smith the right to name the new species. He chose to name the genus Latimeria in honor of Courteney-Latimer, and the species chalumnae after the river near which Goosen had caught the fish.
Fourteen years passed before another coelacanth turned up, despite Smith's peppering the eastern coast of Africa with posters describing the coelacanth and offering a reward. Eventually, in 1952, a second coelacanth was caught near the Comoro Islands in the Indian Ocean, many miles from where the first specimen had been caught off eastern South Africa. Smith thought that the second specimen represented another species, which he named Malania anjouanae. However, later scientists deduced that Malania was actually another specimen of Latimeria.
Since that second specimen, more than 200 additional coelacanths have been caught. Many of these are now in research collections, particularly in France, which had ruled the Comoros as a colonial power. Most coelacanths have been caught by local fishermen, using a handline from a dugout canoe. Unfortunately, the hooked fish quickly die, because of the great pressure difference between its deepwater habitat and the surface.
Some people have thought that catching a live coelacanth to display in an aquarium would be a good idea. Others, including Hans Fricke, have objected to this possibility, arguing that the numbers of coelacanths already taken from its small population have adversely affected the species. Part of the problem is that these animals only bear a few live young at a time, so their fecundity is highly limited and cannot sustain much mortality. Because of these objections, the American and British aquariums that had been considering an expedition to capture a breeding pair of coelacanths changed their minds. An Asian aquarium that did mount such an expedition was unable to capture any live fish.
The coelacanth is protected under the Convention on International Trade in Endangered Species (CITES). However, interest in this unusual fish continues and appears to have created a black market in coelacanth specimens. Unless the government of the Comoro Islands decides to vigorously preserve the endangered coelacanth, instead of allowing continued exploitation, the future of this "living fossil" is not encouraging.
As was just described, living coelacanths were only known from cold, dark waters 1,300-2,000 ft (400-600 m) deep off the Comoro Islands, near the northern tip of Madagascar. Remarkably, however, in 1998 another population of coelacanths was discovered in deep water off the Indonesian island of Sulawesi. Incredibly, the extremely rare fish was incidentally noticed in a local village market by an American zoologist, Mark Erdmann, who was on a honeymoon vacation. The two known populations of coelacanths are located 7,000 mi (11,200 km) apart, and are likely different species. Essentially nothing is known yet about the behavior, ecology, or abundance of the newly discovered population of coelacanths.
F. C. Nicholson