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Coelacanth

Coelacanth

A coelacanth (pronounced SEE-luh-kanth) is a large, primitive fish found in the Indian Ocean. Described as a "living fossil" and once thought to be extinct, this deep-sea fish is believed to form one of the "missing links" in the evolution from fish to land animals.

An "extinct" discovery

Until December 1938, the coelacanth was known only by the fossil record that suggested it had lived as long as 350 million years ago in what is called the Devonian period, and that it probably went extinct some 70 million years ago. It was identified scientifically as part of the extinct sub-class of Crossopterygii (pronounced kross-op-teh-RIH-jee), which means a "lobe-finned fish." Until 1938, most scientists believed the coelacanth had disappeared along with the dinosaurs at the end of the Cretaceous (pronounced kree-TAY-shus) period. However, during that year, fisherman off the eastern coast of South Africa caught a 5-foot (1.5-meter) fish with deep-blue scales and bulging blue eyes that was strange enough to make them bring it to a local museum. The curator, Courtney Latimer, could not identify it, but knew that it was important enough to contact J. L. B. Smith, a leading South African ichthyologist (pronounced ik-thee-OL-low-jist), a zoologist who specializes in fishes. Smith then pronounced the fish to be a coelacanth, and this "living fossil" became the zoological find of the century. Soon after the discovery and publicity, other fisherman from nearby islands were reporting that they too had caught these strange fish that were not good to eat.

Words to Know

Carnivorous: Meat-eating.

Extinct: No longer alive on Earth.

Missing link: An absent member needed to complete a series or resolve a problem.

Missing link between fish and mammals?

One of the reasons that this discovery caused so much excitement was that in 1938 the coelacanth was thought to be a direct ancestor of tetrapods (pronounced TEH-truh-pods), or four-limbed land animals. This was believable because the coelacanth is unlike any other fish. Coelacanth means "hollow spine" in Greek, and, in fact, this strange creature seems to be a combination of two very different types of fish: those that are made of cartilage, like sharks, and all the other regular bony fishes. Its backbone is a long tube of cartilage instead of being a rigid backbone, yet it has a bony head, teeth, and scales. It is a carnivorous (pronounced kar-NIH-vor-us) predatormeaning that it catches, kills, and eats its live preyand has impressive jaws and rows of small, sharp teeth. Most important, it has four muscular, limblike fins underneath its body that it uses like legs to perch or support itself on the ocean bottom. This led some to believe that it actually used these jointed fins to "walk" on the bottom like a four-legged animal. However, recent molecular analysis indicates that the lungfish, instead of the coelacanth, is genetically the closest living fish that is a relative of land animals.

The modern coelacanth

Since that first discovery of a living coelacanth in 1938, additional coelacanths have been caught not only off the southern tip of Africa but off Sulawesi, Indonesia, as well, suggesting that they are more numerous than believed. Today's coelacanths are larger than those found as fossils, and they can grow to be more than 5 feet (1.5 meters) long and weigh as much as 180 pounds (82 kilograms). Scientists still do not know a great deal about them, and it was not until 1975 when a female was dissected that scientists learned that the coelacanth gives birth to live "pups." Zoologists believe that females do not reach sexual maturity until after 20 years of age and that the gestation (pronounced jes-TAY-shun) period, or the time it takes to develop a newborn, is about 13 months. Females give birth to between 5 and 25 pups, which are capable of surviving on their own after birth.

Although there are more coelacanths than at first supposed, they are still recognized as an endangered species. The main reason for this is that they are a highly specialized species that has adapted itself to a narrow habitat range. This means that they can only survive in the cool, deep watersover 650 feet (200 meters) deeparound volcanic islands. Further, they are a highly specialized fish, resting in lava caves during the day and hunting and feeding at night. Although they move with slow, almost balletlike motion, they are excellent predators who can move surprisingly fast when they ambush a smaller fish for a meal. Along with the nautilus (pronounced NAW-tih-lus) and horseshoe crab, the coelacanth is one of the "living fossils" of the sea, since they have changed little from their ancient ancestors.

[See also Fish ]

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coelacanth

coelacanth A bony fish of the genus Latimeria, which was believed to be extinct until 1938, when the first modern specimen of L. chalumnae was discovered in the Indian Ocean around the Comoros Islands, off the SE coast of Africa. A second species, L. menadoensis, was discovered in 1999 in the Celebes Sea, SE Asia. The coelacanth belongs to the same order (Crossopterygii – lobe-finned fishes) as the ancestors of the amphibians. It is a large fish, 1–2 m long and weighing 80 kg or more, with a three-lobed tail fin. The body is covered in rough heavy scales and the pectoral fins can be used like crutches to help movement across the sea bed. The young are born alive. Fossil coelacanths are most abundant in deposits about 400 million years old and no fossils less than 70 million years old have been found.

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coelacanth

coelacanth a large bony marine fish with a three-lobed tail fin and fleshy pectoral fins, found chiefly around the Comoro Islands near Madagascar. It is thought to be related to the ancestors of land vertebrates and was known only from fossils until one was found alive in 1938.

The name is recorded from the mid 19th century, and comes via the modern Latin genus name from Greek koilos ‘hollow’ + akantha ‘spine’ (because its fins have hollow spines).

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coelacanth

coelacanth Bony fish of the genus Latimeria. Thought to have become extinct 60 million years ago, it was found in deep waters off the African coast in 1938. It is grey-brown with lobed fins that have fleshy bases. The scales and bony plates are unlike those of modern fish. Length: 1.5m (5ft). Order Crossopterygii; species Latimeria chalumnae.

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coelacanth

coe·la·canth / ˈsēləˌkan[unvoicedth]/ • n. a large, bony marine fish (Latimeria chalumnae, family Latimeriidae) , found chiefly around the Comoro Islands. It was known only from fossils until one was found alive in 1938.

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coelacanth

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coelacanth

coelacanth: see lobefin; fish.

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coelacanth

coelacanth See COELACANTHIFORMES.

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Coelacanth

Coelacanth

The first, astonishing find

Resources

Coelacanths are the only living representatives 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.

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 lanternfish 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. Frickes research strengthened

the evidence that the rostral organ of coelacanths is an electrical sensor.

The first, astonishing find

A living coelacanth (Latimeria chalumnae ) first came to the attention of science in 1938. At the time, a young biologist named Marjorie 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 shed 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 museums 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 J.L.B. Smith, an expert on South African fish. Smith recognized the fish as a coelacanth from a sketch provided by CourteneyLatimer. 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 Smiths 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. The IUCN lists Latimeria chalumnae as critically endangered.

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 have now been confirmed to be two species. The new Indonesian species is named Latimeria menadoensis. Essentially nothing is known yet about the behavior, ecology, or abundance of the newly discovered species of coelacanth.

Resources

BOOKS

Forey, P. History of Coelacanth Fishes. London: Chapman & Hall, 1998.

Musick, J.A., M.N. Bruton, and E.K. Balon, eds. The Biology of Latimeria chalumnae and the Evolution of Coelacanths. Dordrecht: Kluwer, 1991.

Thompson, K.S. Living Fossil: The Story of the Coelacanth. New York: W.W. Norton, 1991.

PERIODICALS

Holder, M.T., et al. Two Living Species of Coelacanths? Proceedings of the National Academy of Sciences U.S.A. 96 (1999): 1261612620.

F. C. Nicholson

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Coelacanth

Coelacanth

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.


The first, astonishing find

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

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Coelacanth

Coelacanth

Latimeria chalumnae

phylum: Chordata

class: Osteichthyes

order: Coelacanthiformes

family: Latimeriidae

status: Critically endangered, IUCN

range: Comoros, Mozambique, South Africa

Description and biology

Biologists (people who study living organisms) call the coelacanth (pronounced SEE-la-kanth) a "living fossil." This fish is the only living member of an order that was abundant 80,000,000 to 370,000,000 years ago. A stocky fish, it is brown to steel-blue in color. It has large, rough scales and muscular lobes at the base of its fins. The coelacanth grows to a length of 5 feet (1.5 meters) and can weigh up to 150 pounds (68 kilograms). It feeds on lantern fish, cuttlefish, and other reef fish.

Like its relatives the lungfishes, the coelacanth can sense an electric field through an electroreceptive organ in its snout. When it encounters an electric field, it assumes an unusual "headstanding" position: it tilts so its head points downward and its tail points upward. Biologists believe this might be a technique the fish uses to detect prey hiding in the seabed.

A female coelacanth does not lay eggs, but gives birth to fully formed young after a gestation (pregnancy) period of over 12 months. Between 5 and 26 offspring are born at a time, each measuring about 15 inches (38 centimeters) long at birth. Young coelacanths probably live in caves and hunt at night. The fish reach sexual maturity at about 12 to 15 years of age and may live up to 80 years.

Habitat and current distribution

Coelacanths have been found in the waters off the coasts of South Africa, Mozambique, and Comoros (group of islands between northeastern Mozambique and northwestern Madagascar). The greatest concentration of these fishes seems to be around Comoros, especially near the western coast of Great Comoro Island. Biologists have found it difficult to determine the exact number of coelacanths currently in existence. They estimate the total population to be between 200 and 300.

Coelacanths inhabit caves and steep, rocky drop-offs at depths between 400 and 1,000 feet (122 and 305 meters). Some of these fishes have been recorded at depths of almost 2,300 feet (700 meters). They congregate in caves during the day and emerge at night to hunt for food. A single coelacanth may cover a stretch of coastline over 5 miles (8 kilometers) in length in one night.

Habitat and current distribution

In 1938, an unusual fish was caught by fishermen off the eastern coast of South Africa. British amateur ichthyologist (scientist who studies fishes) James L. B. Smith identified it as a coelacanth. Scientists had previously thought this fish had been extinct for 80,000,000 years. In 1952, biologists found coelacanths living and breeding off Comoros. It was then discovered that native inhabitants of the islands had been catching and eating the fish for years.

Word of these discoveries soon spread. Museums, aquariums, and private collectors quickly sought the elusive fish, paying high prices. The number of coelacanths caught increased each year, reaching a high of 11 in 1986. In 1989, the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES; an international treaty to protect wildlife) granted the fish Appendix I status. This banned the trade of the fish between nations that had signed the treaty.

In recent years, coelacanths have been caught and then sold illegally in eastern Asia. People in the region believe fluid from a certain part of the fish's body promotes longer life in humans.

The Coelacanth Conservation Council, established in 1987 in Moroni, Great Comoro Island, promotes public education programs coordinates research, and organizes protection efforts for the endangered coelacanth.

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