Published online 1 October 1998 | Nature | doi:10.1038/news981001-1

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Coelacanth discovery in Indonesia

On 30 July this year, a fisherman called Om Lameh Sonathan and his 10-strong crew caught a strange fish in deep water off the small volcanic island of Manado Tua in Sulawesi, Indonesia. The 29-kilogram, 124-centimetre fish was an unusual catch - for it was a coelacanth, a rare ‘living fossil’ whose only other known population is 10,000 kilometres away, in the Comoro Islands in the western Indian Ocean.

The discovery of coelacanths in Indonesia changes our outlook on the conservation status of a fish that looks very much as its ancestors did, 370 million years ago, and which was believed to have become extinct about 70 million years ago - until a living specimen was netted off South Africa sixty years ago, startling the zoological world.

The Indonesian fisherman took the fish to Mark Erdmann, a postdoctoral researcher from the University of California, Berkeley, who has been working in Sulawesi for several years. He had been on the track of a live coelacanth for ten months, ever since his wife had spotted one in a fish market in Manado, Sulawesi - equivalent to seeing a unicorn in your garden - and had managed to take a few photographs before the fish was sold. Erdmann pursued the elusive fish by first interviewing local fishermen, several of whom claimed to have caught what locals call raja laut - the ‘King of the Sea’.

The fish netted by Om Lameh Sonathan and his crew was still alive by the time it reached Erdmann, who shot six reels of film of the still-swimming creature. Once the animal had died, Erdmann froze it and managed to store tissue samples in liquid nitrogen for later study.

“Our discovery of an Indonesian population of coelacanths challenges the notion that there is a single, unique population of these unique animals in the far western Indian Ocean and holds hope that other populations may exist throughout the Indo-Pacific”, says Roy Caldwell of the University of California, Berkeley, Erdmann’s colleague.

Caldwell, Erdmann and colleague M. Kasim Moosa from the Indonesian Institute of Sciences in Jakarta officially announce the discovery of the Indonesian coelacanth in the 24 September 1998 issue of Nature.

The tale of the coelacanth is strange indeed, and shows that the deep sea is full of surprises. Coelacanths were known for decades, but only as fossils. They appeared in the fossil record around 370 million years ago, had their heyday in terms of species diversity around 220 million years ago, and went into a long sunset that appeared to end with extinction, around 70 million years ago - just before the dinosaurs themselves perished.

Although coelacanths occupied many habitats in the sea and in fresh water, they always adopted a rather conservative appearance, similar to the very earliest species. Deep-bodied and sometimes large, with big, heavy scales, coelacanths look like something straight out of the Lost World.

Prominent among coelacanth features are the paired pectoral (fore-) and pelvic (hind-) fins, each with a robust, fleshy base like a little leg. The structure of these fins, among other things, led to the coelacanths’ place in zoology as possible representatives of the stock whence land vertebrates, including ourselves, evolved. Later work has placed coelacanths at a greater distance from the ancestry of land vertebrates, but their place in the hearts of zoologists was assured.

Finding a living coelacanth would be like finding a living dinosaur - yet it happened, on 23 December, 1938, when a specimen was caught in the Chalumna River, near East London, South Africa. That fish was named Latimeria chalumnae, after its place of discovery, and Marjorie Courtenay Latimer, the curator of a local museum who got the first good look at the fish. The finding was described in Nature in 1939. Another 12 years were to pass before a second specimen was found.

After that, it became clear that all the coelacanths being caught came from the Comoro Islands, a small archipelago between Africa and Madagascar, in the western Indian Ocean. Fishermen catch about three or four coelcanths a year in the Comoros: there have been more than 200 catches since 1938. Specimens caught off Madagascar or Mozambique are considered to be strays from the Comoro population, although rumors persist that coelacanths caught off Madagascar might represent a distinct population.

But why the Comoros? Could coelacanths not exist elsewhere? And why the huge geological gap - 70 million years - during which coelacanths must have existed, but are conspicuous by their absence?

One answer could lie in the choosiness of the modern species, Latimeria chalumnae. Judging from its distribution within the Comoros, the fish prefers water that is both deep and cool - around 180 metres and less than 18 °C. In addition, it prefers to live near steep, submarine slopes pocked by caves. The Sulawesi coelacanths seem to prefer the same sort of habitat. But such pickiness is not extreme: there are probably many suitable places in the Indo-Pacific region that might yet harbour coelacanths.

Another answer is that the fossils of deep-sea fish of any kind, not just coelacanths, are scarce in the geological record. Historically, coelacanths occupied a variety of ecological niches, but deep-sea coelacanths are unlikely to have been preserved at all.

A third answer is that coelacanths are rare, even in places where they are known to occur. Even in the Comoros, catching a coelacanth is still not a commonplace. What this says about the conservation status of the species is unclear - either the species really is endangered, or it is very shy, and generally good at keeping out of harm’s way.

A fourth answer may lie more with ourselves than with the coelacanths. While the coelacanths were considered extinct, nobody would have looked systematically for a live one. Why should they? Finding a living coelacanth would have been considered as futile a quest as hunting a live Tyrannosaurus. The rediscovery of the coelacanth could only ever have been an accident.

And when coelacanths were found in the Comoros, people celebrated the mere fact of their existence, and were less inclined to search for them elsewhere. And if they did, where would they start looking? With just one population to study, nobody had any idea how to estimate the animal’s total geographic range. In truth, they could be anywhere and everywhere. Stories emerged of coelacanths elsewhere in East Africa, even in the Mediterranean - stories that remained unconfirmed fishermens’ tales.

The discovery of a second population gives the problem a badly needed dose of perspective. The researchers think that the Indonesian coelacanths probably belong to Latimeria chalumnae, but have certain differences: the Comoro coelacanth is blue-grey in colour, the Indonesian version is more of a brown shade, with golden flecks. Studies of DNA should settle that issue.

At the same time, the discovery makes a search for coelacanths in the Indian Ocean, and perhaps the western Pacific, a credible proposition. It also is something to give hope to conservationists: it is easy to destroy one, isolated population - to destroy two is much harder.

But the final lesson must be that the ocean is huge enough to conceal, with ease, many of its mysteries from prying eyes. To have found live coelacanths at all is comparable with finding live plesiosaurs, or live ammonites. Who knows what secrets the oceans may not yet yield?