By Ellen Bartlett
CAPE TOWN, South Africa - The island republic of the Comoros, in the western Indian Ocean, is known for its instability - political and seismic. It has 24 political parties, none in control. In 22 years of independence from France, there have been 17 coups or coup attempts. Two of the three islands in the republic seceded recently and the government has been dissolved.
Mt. Karthala, on the island of Grande Comore, is one of the world's largest active volcanos, erupting every 20 years or so. Its last eruption was in 1975 and so it is overdue for another.
But in the deep ocean off the west shore of Grande Comoro, in the cool canyons and overhangs and crevices that slope steeply into darkness, is a living contradiction to the chaos above, a biological symbol of endurance.
The last of the coelacanths swims in the slow lane. Pale blue with irridescent white markings, reaching five feet in length, it is the last example of the crossopterygians, whose fleshy limb-like fins were the probable precursors of arms and legs. fishes. It is the end of the line that some scientists believe gave rise to the first tetrapods, or four-legged, land-dwelling vertebrates.
Assumed to have died out with the dinosaurs in the mass extinctions at the end of the Cretaceous period 65 million years ago, the coelacanth first resurfaced in 1938 in the net of a fishing trawler off East London, South Africa. It was the marine equivalent of stumbling across a living dinosaur.
But as the 60th anniversary of its discovery nears, the venerable fish is in danger of extinction, this time for real. The islands' fishermen are killing it off, though unintentionally.
The species was highly successful in its heyday about 400 million years ago - there are 125 species of coelacanth in the fossil record - but only one species is known to remain. Latimeria chalumnae exists in a single, tiny, relic population off Grande Comoro, at as far down as 2, 000 feet.
Others have been caught, off South Africa, Mozambique and Madagascar, but they are believed to be strays from the Comoran group.
Marine biologist Hans Fricke and his colleagues from the Max Planck Institute in Germany have been following the Comoran coelacanths for 10 years, conducting surveys from a submersible vessel. They have identified more than 100 fish individually, and tagged more than a dozen.
Their early surveys, from 1987 to 1991, showed a stable population of as many as 650 fish. But by 1994, the number in their census area had dropped 30 percent. Then researchers also learned that the coelacanths' range was more limited than believed, pushing estimates lower.
In a paper to be published early next year in the journal ''Conservation Biology,'' Fricke and colleague Karen Hissman estimate the population at less than 300 individuals, living along 38 miles of shore. They warn that overfishing is reducing the population at such a rapid rate that the species is critically endangered.
''We think there is not very much time left to do something'' to save them, Hissman said.
If the last coelacanth species dies out, those who study it say, it will be one of the most tragic of modern extinctions.
''Here we have got one of the most significant back-boned animals that ever evolved, and it's going extinct. It could disappear within the next 15 to 20 years and there is no effective conservation measure in place,'' says marine biologist Mike Bruton of the Two Oceans Aquarium. With Fricke, Bruton is a leading authority on the coelacanth.
The killing is not purposeful. The coelacanth is dying out because it keeps getting caught by fishermen who don't even want it.
The target of the traditional fishing industry off Grande Comoro is Ruvettus pretiosus, the oilfish. The oilfish and the coelacanth share a deep water habitat close to shore, swim at the same depths, take the same bait. Until Western science alerted them to its value, Bruton says, fishermen regarded the coelacanth as a nuisance.
At best, it was let go. But because the coelacanth has impressive jaws and rows of small sharp teeth - and hooks are expensive - the more typical response was to beat it death and retrieve the hook before throwing back.
There was a flurry of local interest in the coelacanth after its discovery by scientists. JLB Smith, the South African biologist who described the coelacanth in 1939, posted notices all over the islands, offering 100 pounds for a specimen. His efforts went unrewarded until 1952, when a second coelacanth was caught off the Cormoran island of Anjouan. There were no commercial flights to the islands, so Smith flew up in a South African military Dakota to claim the fish.
Coelacanths were caught in increasing numbers until the 1980s; most were sent to museums and aquaria for study. Scientists were concerned that even in the race to get specimens for research, they were endangering the species.
There was a drop in the number of coelacanths caught in the 1980s, a side effect of international efforts to help the impoverished Comorans develop their fishing industry. The European Community and the Japanese funded the construction of special floats, known as fish aggregation devices, to attract commercial fish species to new fishing grounds well offshore of the over-fished, close-in waters. Because the new fishing grounds were beyond the reach of the canoes, the group also paid for boats with outboard engines.
But the project ended. The engines broke down, and there was no one to fix them. The fishermen went back to their old dugouts, and back to fishing the inshore waters. They started hooking coelacanths again, and the population went on the sharp decline that continues today. Scientists also think that overfishing may slowly be robbing the coelacanths of their prey species, and high levels of insecticides have shown up in coelacanth tissue. The toxins are thought to have traveled via air from the African continent.
If the coelacanth disappears, it will do so leaving many questions unanswered, among them the fish's place in prehistory. Was it the coelacanth, with its primitive limb-like fins, or the lungfish, capable of breathing air as well as deriving oxygen from water, that is closer to the evolutionary line that led to amphibians, and thus to the rest of the tetrapods, including ourselves?
Those favoring the coelacanth argue that its blood hemoglobin is similar to that of tadpoles - though not to that of adult frogs. But tests of mitochondrial DNA indicate that the lungfish is our closer ancestor. Mitochondrial DNA, passed down through mothers and obtained from cell mitochondria, is used increasingly in determining relationships among ancient animals. Five species of the ancient lungfish also survive today, in Australia, South America, and tropical Africa.
Unlike the lungfish, which is little changed from its beginnings 460 million years ago, the coelacanth is not the window into the past that its finders had hoped it would be. The living coelacanth may look like its fossil precedessors, but it does not operate like them.
''The coelacanth is a highly specialized, extremely sophisticated animal, which almost certainly is not operating now the way it did 400 million years ago,'' Bruton says. ''It is by no means ancient and primitive...It has found unique solutions to the problems that faced it.''
The coelacanth borrowed from the cartilagenous fishes, like the shark, and the bony fishes, and remains somewhere between the two.
Like the shark, the coelacanth has a spiral valve in its intestine to increase surface area and enhance food absorption. Like the shark, it has a long cartilagenous tube instead of a backbone - what Bruton calls ''a basic coathanger for everything to hang on. '' But it has a bony head, teeth and scales.
It is the only vertebrate with an intracranial joint, a feature once common among frogs, enabling it to raise its top jaw as it lowers its bottom jaw to increase its gape.
Perhaps most intriguingly, the coelacanth gives birth to live young, and did so long before the mammals came along. The females lay a number of eggs the size of oranges, which hatch in utero; the embryos consume their own yolk sac and then, some scientists think, their unhatched siblings. There is some evidence that they obtain nutrition and oxygen from their mothers.
But much remains a mystery.
''We don't even know where the juveniles live, we don't know how often they breed, we don't know the growth rate, we don't know the gestation perod, '' Bruton says.
Most of what coelacanths do is beyond human reach. By day they rest in lava caves. They hunt at night, moving down to depths a half mile or so, beyond the reach of the submersibles and the range of the transmitters on their tags.
Coelacanths operate like the big gliding birds of the air, riding the ocean currents and gyres, making slow circles back to their caves after a hunt. Contray to popular belief, they do not use their flexible fins to walk on the ocean bottom.
They are the ultimate energy-saving species, making up for their poor ability to extract oxygen from the water with an extremely low metabolism. They move slowly, in a way that is almost balletic, Bruton says, ''except when they ambush, and then they have a very fast acceleration.''
The very aspects of their physiology that have served them so well through history are what are endangering them now.
No matter how seriously the Comoran fishing community take the scientists' warnings - and Hissman and others believe they do understand the coelacanth's precarious situation - the only way they can help save the fish is to not hook it in the first place.
''A coelacanth pulled up through 21 atmospheres, from a depth of 200 meters [650 feet], is almost certainly not going to survive,'' Bruton says. ''Firstly, in the hot surface waters of the comoros, 26 degrees centigrade [79 degrees F.], there is so little oxygen that they'd probably asphyxiate. They're already oxygen-deprived from fighting the hook, and probably suffering from lactic acid overdose.''
Few that are caught alive remain alive for long. Bruton, with Fricke and Hissman in Germany, has proposed the construction of new floats to attact fish inshore but closer to the water's surface. This would enable fishermen to fish in safer waters, in their canoes, and reduce the chances of capturing coelacanths.
But, says Bruton, ''It's very difficult to get money to conserve an animal that you can't see, and which tourists can't pay to go and look at....People love conserving the hot and furries, but they don't like conserving the wet and slimies.''
So Bruton and Fricke have come up with another plan to raise public awareness to the plight of the fish. They place a low-light video camera outside the entrance of one of the coelacanths' caves, and broadcast continuous, real-time video of their movements. The video would be shown on screens at an educational center on Grande Comore, and by satellite to the outside world.
Once again, the problem is money. And time is running out.
''The decline, plus the fact that they're highly specialized animals adapted to a narrow habitat range, suggests that they will become extinct,'' Bruton says. ''Within a few more million years the coelacanth probably would have gone extinct anyway, but we are bringing it about within a hundred years of our finding it.''
This story ran on page C01 (front of Science Monday section) of the Boston Globe on 1 December 1997.
Credit: Loren Coleman.