The Coelacanth, a living fossil
A prehistoric fish thought to be extinct suddenly reappears one morning in 1938. What secrets can it reveal to us about the world of 400 million years ago?
The living fossil
One morning in 1938, in the national museum in East London (South Africa), a rather large package was displayed on the desk of the museum curator. The package had been brought by a fisherman.
The museum curator, Mrs. Latimer, cautiously opened the package - almost foreseeing what it contained - and stared at the marvelous contents.
A strange fish with phosphorescent eyes. Its body had a steel blue color, almost metallic, with white spots. The scales had a stony appearance: they were - in fact - very hard, and the teeth were small, numerous, conical and pointed.
However, the state of conservation of the fish was not excellent, in fact it showed extensive traces of ongoing decomposition. Dr. Latimer's analysis continued carefully, while a thin voice began to whisper a name in her mind: coelacanth.
The Coelacanth
The coelacanth is a fish belonging to the order of the crossopterygians, known - until then - only through fossil remains and therefore believed to have been extinct since the time of the dinosaurs.
Crossoptèrygi are a subclass of exclusively fossil osteite fish, with the exception of the genus Latimeria (named after its discoverer, Dr. Latimer), a living coelacanth [the coelacanth, precisely].
According to paleozoology the first crossopterygians date back to the Devonian (395 and 345 million years ago). The skull is similar in anatomy to that of amphibians. They have even fins, in the form of biserial blades, which are articulated by means of a single piece of bone linked to the shoulder and pelvic girdle.
Some are considered precursors of the first terrestrial vertebrates (the stegocephalic amphibians), while others (the coelacanths) did not undergo any evolution after the Devonian. For this characteristic they are defined as living fossils.
This fish can be considered a close relative of the Ripidistidae (today entirely extinct), which abandoned aquatic life in the Devonian to live on the mainland, as at that time there was a great drought which dried up several rivers and lakes, making many others muddy and poor in oxygen: many fish with gills died inexorably.
Part of the Ripidistites (equipped with a very rudimentary lung and very powerful fins) managed to adapt to land. In this era - therefore - the Coelacanth adapted to living in areas poor in food and oxygen. Proof of this is its metabolism; it consumes only 3.8 milliliters of oxygen for every kilogram of body weight every hour.
The table below shows comparisons with other animals: tuna (identical in size) and trout (definitely smaller).
| Species | Milliliters of O2 per kg per hour |
| Coelacanth | 3.8 - [1] |
| Tuna | 484 - [127 times bigger] |
| Trout | 42.5 - [11 times bigger] |
Therefore, the more the metabolism increases, the more oxygen consumption increases as more energy is needed. The coelacanth, by saving its strength and reducing its metabolism to a minimum, managed to overcome extinction.
James Smith's Confirmation
To be sure of the intuition, Dr. Latimer consulted the most famous South African ichthyologist, James Smith, who confirmed the exceptional discovery: it was indeed a living specimen of Coelacanth.
The discovered animal, according to the analyzes conducted, had kept its physiology unchanged, remaining identical to the same specimens that lived in the Mesozoic era (from 254 million to 64 and a half million years ago).
To carry out more in-depth studies, it was necessary to have a coelacanth in excellent condition and therefore an extensive search was carried out in the area where the specimen had been caught. However, expectations were disappointed, as no other specimens were caught.
Subsequent discoveries
In 1952, however, another specimen of Coelacanth was caught off the coast of the Comoros Islands (near Madagascar - Indian Ocean). The news, however, did not end with the discovery of the fish, because shortly thereafter it was learned that the local natives knew that fish well, to the point that they used to cook it and eat it in brine and used its hard skin as paper abrasive. The specimens that it was possible to fish off the coast of the Comoros islands were numerous. It became clear to scholars that in the depths of those islands there was an entire colony of that wonderful fish, but nevertheless nobody had been able to understand or learn about the life habits of the Coelacanth.
In 1987, technology came to the aid of scholars: using a bathyscaphe it was possible to descend into those seabeds and study the movements and habits of the Coelacanth right in its environment. The date of the first actual sighting of the Coelacanth was January 17, 1987. Towards the late afternoon, a specimen measuring approximately 1.5 meters passed in front of the porthole of the bathyscaphe Geo. The bathyscaphe lay at about 198 meters deep, there were - subsequently - few other sightings due to the excessive depth to which this fish liked to go, the bathyscaphe was not able to exceed 200 meters deep.
The scholars did not lose heart and, thanks also to an intense awareness campaign, they managed to obtain a new bathyscaphe, the Jago, capable of reaching 400 meters of depth. With this new bathyscaphe they dived following a steep slope of lava which, around 250/260 meters, was covered by a very fine sandy sediment. Along this slope another exceptional discovery occurred: the coelacanth's burrows, masterfully hidden between the horizontal cracks in the wall.
The fish itself demonstrated a formidable adaptation to the seabed and amazing camouflage skills.
Peculiarities and characteristics of life
The white spots in their bodies have a very important function, varying from individual to individual. They act as fingerprints, making it possible to study individual animals and allowing the consistency of the colony to be numerically verified. Thanks to these spots, it was possible to identify certain fishes and follow them more directly in their habitat. This allowed us to discover that Coelacanths live in caves that they leave only at night, in no more than four individuals. Scholars have understood that this coexistence is forced and does not respond to any social scheme, as the coelacanth is a solitary animal.
A very interesting characteristic of Coelacanths is that in caves they remain perfectly still, they let themselves be carried by the currents and - every now and then - they skilfully move their fins to avoid touching each other (it has been noticed that if two coelacanths accidentally touch each other, they both withdraw very quickly the fins taking on an extremely defensive attitude overall).
The cave - therefore - is their home, which is abandoned in the evening, when the coelacanths come out of their den to go pooping, pushing into the sea depths in search of red mullet, sea bream or other fish they like. Their way of diving towards the depths is reminiscent - even if vaguely - of what some birds adopt when they descend from the air to the ground: they make more or less wide turns, descending a few meters for each turn made. The depth that, however, is reached by these fish is on average around 300 meters. However, their hunting territory is much larger in the width sense, in fact they move (always in a circular manner) for a radius of about eight kilometers from the den. However, the den is not a fixed home, but the closest one is chosen in the morning, which is why coexistence between coelacanths is forced: for them the cave (den) is a place where they only spend the daytime hours.
Scientists are still uncertain about the method used by these fish to orient themselves among the seabed at night. Among the many explanations the one that seems - for now - to receive the greatest consensus is the one that believes that the ancient lava (material of which the slopes where the coelacanth caves are made) creates forms of particular magnetism that the coelacanth is capable of to perceive.
How the Coelacanth hunts
The coelacanth does not take half measures in its hunting trips: little technique and a lot of strength mean that very few preys manage to escape. As soon as it sees prey in front of it, the coelacanth accelerates lightning-fast, opens its mouth wide (thanks also to a special joint between the bones of the skull hitherto only found on fossil remains) and swallows the prey in a single bite.
Since the coelacanth only moves at night, the problem arose of how it can "see" its prey, considering that absolute darkness reigns at around 200 meters deep. The scholars started from the fact that the coelcanthus (a saver of energy to the point of excess) attacks only the prey placed in front of it, its action is rapid and calculated and above all precise.
After months of studies, they managed to identify a sensor at the end of the head which they called rostral organ. This organ, it seems, is able to perceive the small electrical discharges emitted by the muscular contractions of the fish that swim in front of the coelcanth, now providing the exact position of the prey to be attacked.
The Coelacanth thought to be extinct, has instead forcefully returned to prominence, demonstrating that adaptation or evolution is not always necessary for the conservation of a species. The research on this fish is obviously not finished. This has perhaps given too much publicity to this animal which now risks, in just a century, what time has failed to do in 400 million years: extinction. Huge numbers of Coelacanths lie stuffed on stands near the Comoros Islands.
