(18-01-10) The record of fossils has numerous examples of species that one day populated the planet and ended up extinguished, because their environment was destroyed by a planetary catastrophe, or maybe because new species better adapted occupied their ecological niche.

    This is the rule imposed by natural selection and only those called “living fossils”, it is, species that survive from ancient times, are able to avoid it. The most representative example of these exceptions to the general rule is the coelacanth (Latimeria chalumnae). According to the fossil record, this type of fish appeared in the Devonian (400 million years ago) and reached its splendour in the Carboniferous (250 million years ago).

    From the Late Cretaceous (65 million years ago) there is no known fossil of coelacanth, so it was believed that this fish had became extinct. However, on 22 December 1938, Marjorie Courtenay-Latimer, curator of the local museum, discovered among the fishes unloaded at the docks of the city of East London (South Africa), a fish whose most distinctive feature was the possession of lobed fins (normal fish have fins with rays).

    The amazing resemblance of the fish with coelacanth fossils allowed a quick identification. The second specimen of coelacanth appeared at the end of 1952 in the Comoros Islands, located in the Indian Ocean between Madagascar and Mozambique. The appearance of new specimens in subsequent years confirmed the existence of a stable population of the species in the archipelago.

    Until 1998 it was believed that this one was the only existing population of coelacanths in the world. Again, the scientific world was surprised when Mark V. Erdmann, a biologist at the University of California in Berkeley, demonstrated the existence of coelacanths in Manado Tua, one of the Celebes Islands (Sulawesi, Indonesia). It was the Indonesian coelacanth (Latimeria menadoensis).

    Celebes Islands are nearly 6,200 miles away from the Comoros Islands. Therefore, this finding considerably extended the geographical distribution of the coelacanth, which could have several populations along the Indian Ocean or even in other seas.

THEY TALK ABOUT LUMINISCENT SPECIMENS

    Currently, numerous specimens have been captured in areas close to the two islands of the Comoros archipelago and also in Sulawesi (Indonesia), Kenya, Tanzania, Mozambique, Madagascar, Sulawesi and the Lucia Wetland Park (South Africa) . They even have found different specimens, some with bioluminescence. The problem of the study of these specimens was that they often burst due to pressure differences, and the samples were very defective.

    The latest news about this species was last November, when the “Coelacanth Expedition” in the Comoros with Dr. Hans Fricke, aboard the yacht Octopus, equipped with a submersible robot, found a shoal of very young coelacanths 820 feet deep. When he was going to film them in HD they had to leave the robot and run away because they were attacked by pirates.

    Fricke says that “it was a shoal of young fish and close to them there were adults, some hidden in a cave. I had never seen a similar concentration. It is a pity that we could not shoot a single second of that discovery.” When there is more security in the area, the “Coelacanth Expedition”" will return to the place where they lost the ROV to look for it with another one while looking for coelacanths.

    Current coelacanths are very similar to their fossil relatives: they are large marine fish (3,94 ft-4,27 ft) bluish gray or sometimes yellow. It is assumed that they usually live in waters between 500 ft. and 1000 ft deep. During the day they shelter in underwater caves made of lava from volcanic eruptions and that in the evening they go up to the surface in search of reef fish that make up their food.

    From its external anatomy they highlight the pair of lobed fins, with great ability to rotate and a symmetric tail with a typical apical lobe. From the internal anatomy, the possession of a swim bladder that contains oil allows it to dive at big depths.

THEY DO NOT REACH SEXUAL MATURITY UP TO 20 YEARS OF AGE

    Reproductive behaviour is not known with accuracy. It is believed that its sexual maturity does not occur until they are 20 years old. They are ovoviviparous with internal fecundation, and the eggs can be up to 4 inches long and weight up to 300 g. Gestation period lasts about 13 months, and after it the female gives birth to 5 to 25 calves quite developed, able to survive, and they do not take care of them.

    The population of the Comoros has about 200 specimens, and there are no data from the population of Indonesia.

    Coelacanths have a great evolutionary importance since they, together with lungfish, are the closest living relatives from terrestrial vertebrate or tetrapods. The transition from aquatic to terrestrial environment, which took place in the upper Devonian, 360 million years ago, was one of the most important episodes in the natural history of vertebrates, since it involved numerous morphological, physiological and ethological or behavioural changes and lobe-finned fish were the protagonists.

    In 1989 it was estimated that the total population of coelacanths in the Comoros was approximately 200 individuals. Nevertheless, between 1991 and 1994 the number of observed coelacanths dropped alarmingly. The most likely cause of this decline was overfishing in the area, which caused a significant reduction in the number of species that coelacanths can feed on.

 

IT IS A VERY VULNERABLE SPECIES

    Furthermore, the intrinsic characteristics of the biology of the coelacanth (complex reproductive cycle, with internal fertilization, development of few embryos inside the female and a very long gestation period) contribute to its vulnerability and make this species be a candidate to extinction.

    Finally, the belief in some Asian countries that the liquid inside the backbone of the coelacanth can prolong life is another great responsible of maintaining a thriving black market of products of coelacanth.

    The future of the coelacanth is uncertain. This fish, which survived mass extinctions that occurred over the past 400 million years, is facing its greatest danger: human being. However, we have still time to avoid their extinction. Strict protection of the coasts of the Comoros should slow down the decline of this population.

    Also, the discovery of the population of Indonesia is a relief for the conservation of the species. Nonetheless, it is necessary to take specific measures to avoid the repetition of dispossession and decline occurred in the Comoros Islands. With some luck, this living fossil can continue to defy the extinction some few million years more.

 

Text: Guadalupe Romero / MWN

TAXONOMY
Kingdom: ANIMALIA
Phylum: CHORDATA
Class: SARCOPTERYGII
Order: COELACANTHIFORMES
Family: LATIMERIIDAE
Scientific name: Latimeria chalumnae
Author of the species: Smith, 1939
Synonym: Malania anjouanae
Common names:
Spanish: Celacanto
English: Coelacanth, Gombessa
French: Coelacanthe
South Africa: Seelakant.