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| Latimeria chalumnae (Elizabeth Morales) |
Any of various mostly extinct fishes of the order Coelacanthiformes, known only in fossil form until a single living species, Latimeria chalumnae of African marine waters, was identified in 1938.
[New Latin Coelacanthus, former genus name : Greek koilos, hollow; see –coel + Greek akantha, spine.]
coelacanthine coe'la·can'thine' (-kăn'thīn', -thĭn) adj.(Coelacanths)
Class: Sarcopterygii
Order: Coelacanthiformes
Number of families: 1
Evolution and systematics
The living coelacanths are often celebrated as the most unusual case and important example of animal evolution. The first fossil coelacanths were recognized in rocks between 380 and 75 million years old. More than 100 years ago Woodward published the first review on these fishes. Fossils younger than 75 million years were never found, as if all coelacanths had become extinct at that time, very much like the dinosaurs. The bony structures in these fossil crossopterygians, especially their paired (pectoral and pelvic) fins, placed them close to the ancestor of the first amphibians and all other land vertebrates.
It is of no surprise, therefore, that the December 1938 find of a living coelacanth, when announced to the world by J. L. B. Smith in March 1939, caused disbelief and created one of the greatest biological sensations of the last century. Finding a living coelacanth—morphologically so similar to the fossil specimens left in rocks more than 75 million years ago—was as inconceivable as meeting a living dinosaur on a weekend walk.
The living coelacanth, sometimes known by the common name "gombessa," is a single advanced life form that has survived with relatively little change for nearly 400 million years. While some of the coelacanth's relatives became implicated in the ancestry of all terrestrial vertebrates, the aquatic descendants developed structural solutions to life absent in other animals. For example, instead of the calcified vertebrae that normally reinforce the axial skeleton, the coelacanths evolved a strong-walled elastic tube that is as far transformed from the notochord as are the vertebrae. Instead of a solid braincase, they evolved a two-part neurocranium with an intracranial joint that is operated by a special basicranial muscle. It is the only animal with that structure living today. This intracranial joint and other unique rotational joints in the head together with the rostral organs and the gular reticulate electrosensory system may explain the special suction feeding and head standing behavior observed by Hans Fricke.
In the synthesis of coelacanth evolution by P. Forey, a total of 83 species are recognized to have lived between 380 million years ago in the middle Devonian and 75 million years ago in the Upper Cretaceous. There is no fossil record of coelacanths from the past 75 million years. During that time coelacanths lived and died without leaving fossils. The highest diversity of coelacanths during their geological history was recorded in the Lower Triassic (16 species) and in the Upper Jurassic (8 species). While most fossil remnants were found in marine deposits, many were also found in freshwater deposits, especially in the Upper Carboniferous, Lower Permian, Upper Triassic, Jurassic, and Lower Cretaceous.
The first living coelacanth that came to the attention of scientists was named Latimeria chalumnae by J. L. B. Smith in 1939. Upon seeing a second specimen in 1952 and noting that it lacked the first dorsal fin, Smith considered it a new species and named it Malania anjouanae. When it was found later that except for the lack of the first dorsal fin all other structures were like the first specimen, it was concluded that this first dorsal fin was probably bitten off by a shark, and Malania anjouanae become a synonym of Latimeria chalumnae.
A second species of coelacanth, Latimeria menadoensis, was discovered near Sulawesi by M. V. Erdmann in 1998.
At the beginning of the twenty-first century, one family was recognized: Latimeriidae. It contains one genus (Latimeria) and two species: Latimeria chalumnae and Latimeria menadoensis.
Physical characteristics
The living coelacanth is often referred to as a "living fossil." A representative of an ancient group whose other members have all gone extinct, it has survived for millions of years with a virtually unchanged body form. Studies of the living coelacanth's soft anatomy and body fluids have shown various similarities with chondrichthyans. These characteristics are thus considered "primitive vertebrate features," but the coelacanth has also developed many specialized characteristics.
Coelacanths have several unique characteristics, the most obvious of which are the fleshy (lobate or pedunculate) fins. While these fins have some similarity with the lobate fins in fossil lungfishes, rhipidistians, and some polypterids, no other fish group has developed seven fleshy fins. The paired fins are supported by girdles that resemble the purported precursors of the pectoral and pelvic girdles of tetrapods. The axial skeleton of coelacanths evolved differently from that of other vertebrates, even those with a persistent notochord. Instead of developing vertebrae, the notochord of the living coelacanth developed into a tube, over 1.57 in (4 cm) in diameter in adults, which is stiffened by fluid under pressure.
The skull of coelacanths has an intracranial joint that divides the neurocranium into an anterior and a posterior half and that allows the mouth to open not only by lowering the lower jaw but also by raising the upper jaw. This increases the gape considerably, and by extending the buccal cavity creates a strong suction. No other living animal has this feature.
Adult coelacanths have a minute brain (occupying only 1.5% of the cranial cavity) in common with many deep-sea sharks and the sixgill stingray (Hexatrygon bickelli). The pineal complex, which is involved with photoreception in many vertebrates, is relatively primitive and undifferentiated in Latimeria, whereas the basilar papilla in the inner ear has some similarity to that of tetrapods. The electrosensory systems in the head and the gular plates, in addition to the rostral organs, might be useful for locating prey.
The coelacanth has a spiral valve with unique, extremely elongate, nearly parallel spiral cones in its intestine. The valvular intestine is a shared character with ancestral jawed fishes (Gnathostomata), progressively reduced in actinopterygians and replaced by an elongated intestine in teleosts and tetrapods. The heart is elongate but is not simple; it is as complex as in other fishes, and far removed from the superficial earlier interpretation as an S-shaped embryonic tube. Bogart, Balon, and Bruton reported in 1994 that a Latimeria chalumnae specimen caught in April 1991 at Hahaya, Grand Comoro, has a 48-chromosome karyotype. This karyotype is unlike those found in lungfishes but is very similar to the 46-chromosome karyotype of one of the ancient frogs, Ascaphus truei.
The complex dermal canals known only from fossil jawless and jawed fishes are combined in L. chalumnae with the common pit lines of superficial neuromasts (lateral line) of extant fishes. Therefore, retention and specialization of ancestral structures, no longer present in other living fishes, is one of the most significant attributes represented, along with their evolutionary persistence, in this true "living fossil."
The coloration of Latimeria chalumnae is bluish grey with large whitish marks scattered on the body, head, and the fleshy fin bases. The white markings are specific to each individual, so each single fish can be distinguished. The white marks simulate white sessile tunicates on the walls of caves where coelacanths aggregate and on the substrate over which they drift, so that the animals blend perfectly with their background. On a dying coelacanth the bluish hue turns brown, the color of all dead specimens. The Indonesian coelacanth was brown when still alive with much golden glitter in the whitish markings.
Females grow to 74.8 in (190 cm), males to 59.1 in (150 cm) and 110–198 lb (50–90 kg). Individuals are 13.8–15 in (35–38 cm) long at birth.
Distribution
Since 1998 the coelacanth distribution is known to be not only in the west Indian Ocean, but also 6,214 mi (10,000 km) east on the other side of the Indian Ocean. The specimen that was caught off the Chalumna River in 1938 was later thought to be a stray from the Comoran population around Grand Comoro and Anjouan. Captures near Malindi (Kenya) and at Sodwana Bay near St. Lucia estuary in South Africa extend the range of intermittent distribution along the East African coast. It has not yet been established whether these are discrete populations. Only the Mozambique specimen and the southwest Madagascar specimens were proven to be of Comoran origin. According to Victor Springer, Latimeria menadoensis in Indonesia is most likely isolated from the western population(s) by unsuitable habitats in the central Indian Ocean.
Habitat
The extant coelacanths are tropical marine fishes inhabiting inshore water below 328 ft (100 m) depth. They seem to prefer steep sloping areas with little coral sand deposits. The hemoglobin of Latimeria chalumnae has the best affinity to oxygen at 61–64.4°F (16–18°C). This temperature coincides with the isobaths of 328–984 ft (100–300 m) in most localities inhabited by coelacanths. As there seems to be very little prey at these depths, the coelacanth is forced to ascend at night to more shallow waters in order to feed, risking some respiratory discomfort. For the daytime, coelacanths descend back into more comfortable temperatures and hide in groups under overhangs and in caves. A sluggish locomotion and drifting instead of fast active swimming probably help to save energy. If this is the case, then a fish hauled to the surface often with a water temperature far above 68°F (20°C) is under such respiratory stress that its survival is uncertain even if it is released back into cooler waters.
At Grand Comoro most coelacanth catches have occurred over the newest lava flows of the periodically erupting volcano Kartala. These lava fields under water consist of more cavities where prey can hide, and more caves for daytime aggregations of coelacanths than other less steeply sloping shores.
Behavior
Coelacanths aggregate in caves and overhangs about 328–656 ft (100–200 m) deep during the daytime. At Grand Comoro 19 adults were counted in one cave close together, gently moving their paired fins but never touching each other. Individuals distinguished by their specific white markings were found faithful to a particular cave for many months, although every day some strayed into other caves. At night the fish drifted individually close to the substrate.
After the first observations in 1987 from the submersible GEO, Hans Fricke noted that at night, all individuals took advantage of up- or down-wellings and drifted slowly with the current. The paired fins stabilized the drifting fish so that "all individuals seemed perfectly oriented in that they avoided obstacles in their environment, apparently detecting them well in advance." Fricke further commented that "all individuals irregularly performed a curious headstand, lasting up to 2 minutes."
During swimming, the coelacanth very slowly moves its paired fleshy pectoral and pelvic fins alternatingly in the manner of a trotting horse (left pectoral and right pelvic simultaneously and then right pectoral and left pelvic together). This pattern is also common to lungfish and a few other bottom-dwelling fishes and, of course, most tetrapods. The unpaired fleshy second dorsal and anal fins are sculled in synchrony from side to side and are the main organs for forward propulsion. This explains their similar shape and exact juxtaposition. The nonfleshy first dorsal fin is usually folded and flush with the dorsal surface in undisturbed fish, but when spread it appears to be used as a sail and/or for lateral display when the fish feels threatened. The large caudal fin (in fact the third dorsal, epicaudal, and second anal) is held rigid during drift-swimming as in weakly electric fishes (to enable interpretation of the electric field distortions), but provides powerful propulsion during rapid forward bursts. The small epicaudal lobe is bent to and fro when the coelacanth is swimming, drifting, or standing on its head, and may be implicated in electro-reception together with the rostral organ and the reticulate organs. The GEO team was able to induce headstands in the coelacanth by emitting weak electric currents from electrodes held in the submersible's remotely controlled arm.
Fin coordination probably developed to stabilize the bulky body of the coelacanth, but could in its extinct ancestors have facilitated the eventual transition to locomotion on land. When coelacanths have been observed coming in contact with the substrate, the paired, fleshy fins were not used for locomotion. The coelacanth probably never walks.
Feeding ecology and diet
Latimeria chalumnae is an opportunistic nocturnal bottom drift feeder. Prey items identified in several studies are benthic or epibenthic dwellers like some lanternfishes, deepwater cardinal fishes, cuttlefishes, snappers, cephalopods, and even a swell shark. Most of these are known to hide in bottom cavities.
The coelacanth prefers fresh lava rocks with cavities not filled by coral sand. Being a sluggish swimmer with a low metabolic rate, it regularly performs intermittent head stands during its nocturnal drifts along the bottom. Latimeria is able not only to move its lower jaw but, thanks to the intracranial joint, to lift its upper jaw. This feature, unique among extant vertebrates, allows for a considerable increase in the oral gape. In addition to the rostral organ the fish has a distinct reticular system in the gular bones under the head that probably also functions as an electro-sensory system.
The cranial morphology of Latimeria chalumnae suggests that it is a gape-and-suck predator whose anatomical specializations appear to permit it to extract prey from the crannies and cavities where it takes shelter.
Reproductive biology
Until 1975 Latimeria chalumnae had been considered to be an egg laying (oviparous) species because a 64.2 in (163 cm) long female caught at Anjouan in 1972 was found containing 19 eggs the size and color of oranges. But then another female, 63 in (160 cm) long, previously caught at Anjouan in 1962, preserved, and kept as an exhibit at the American Museum of Natural History (AMNH), was dissected in 1975. The curators of this museum were persuaded to cut open the specimen in order to sample needed tissue of some inner organs. The curators discovered in the female's oviduct five well-developed embryos, with a length of 11.8–13 in (30–33 cm), each with a large yolk sac. This finding meant that the living coelacanth is a livebearer (viviparous).
Later, John Wourms and Jim Atz studied these embryos and their mother's oviduct in detail and found that the heavily vascularized yolk sac surfaces were in very close contact with the equally densely vascularized oviduct walls, thus forming a simple placentalike structure. It seems, therefore, that in addition to the yolk, the embryos have a second, more direct, way to receive nutrients from the mother. A third way of obtaining nutrients suggested itself when more females were dissected. One 66-in (168-cm) long female contained 59 eggs the size of chicken eggs, another female had 65 eggs, and yet others had 62, 56, and 66 eggs. All these females produced more eggs than their oviduct would be able to accommodate as embryos. While the five embryos from the AMNH female still had large yolk sacs, the 26 fetuses from the female caught near Mozambique were close to term and had only a scar on the belly where the yolk sac once was. Both groups of embryos/fetuses had well-developed alimentary tracts and dentitions. It is thus possible that additional nutrient delivery occurred through the debris from the supernumerary eggs. After all, it is known that in some shark species the fetuses feed on eggs and siblings, so that at the end only one large predator is born. It is possible that such oophagy, as it is called, also occurs in Latimeria.
Further studies of these unborn fetuses revealed exceptionally wide gill-cover membranes full of cells capable of absorbing uterine milk (histotrophes) secreted by the oviduct walls. This type of nutrient transfer is known in some fishes. Finally, the carotenoid pigments in the yolk are also implicated in oxygen delivery. While more investigation is needed, it is clear that the coelacanth is a fish with a very advanced and complex style of reproduction. This is not surprising, given that the Jurassic coelacanth Holophagus gulo was probably a live-bearer, and the Carboniferous Rhabdoderma exiguum, although still oviparous, had eggs of relatively large size.
Circumstantial evidence suggests that the gestation time of the living coelacanth is very long (about 13 months), that the females become mature for the first time when older than 20 years (as in some sturgeons), and that a female does not deliver young every year but several years apart. Scientists do not know how the internal fertilization of a female is achieved and where the young live right after birth and in subsequent years. No young were noticed from the submersibles either drifting or in caves, and only one or two have been collected free swimming.
Conservation status
After the catch of the "second living coelacanth" became known to science in 1952, the Comoro Archipelago (then a French colony) was recognized as the "home" of the coelacanth. Soon, national ownership was declared for all subsequent specimens, and the second one declared stolen from its "rightful" owners. Only the French were allowed to collect them. J. Millot, a spider specialist on Madagascar, moved to Paris and with J. Anthony started detailed anatomical descriptions of the coelacanth. After close to 80 specimens were accumulated, some were used as diplomatic gifts. Eventually, other nationals joined the frenzy of working on the prestigious animal. Several special expeditions converged onto the
Comoros, but luckily the beast could not be caught at will by the methods employed.
The Japanese imported larger fiberglass boats called japavas to supplement the small single log dugout outriggers (galavas), and built a fishing school on Anjouan in the early 1980s. At the same time, rumor was started that the fluid from the "notochord" tube when ingested prolonged life. Soon, in addition to the demands for coelacanths for museum exhibitions, a black market for fresh or frozen specimens for "medicinal" purposes was started. The price soared to $3,000 or more per fish, especially during the rule of the white mercenary who called himself Colonel Baku.
The first deployment of Fricke's submersible GEO and the first sighting of coelacanths in their natural habitat coincided with the urgent need for conservation. The Coelacanth Conservation Council (CCC) was established by Eugene Balon, Mike Bruton, Christine Flegler-Balon, Hans Fricke, and Rafael Plante when they met in Moroni (Grand Comoro), the capital of the Federal Islamic Republic of the Comoros, in 1987. The CCC was inspired by the Desert Fishes Council that led to the most progressive conservation law in the world, the Endangered Species Act of the United States. Within the next two years, members of the CCC managed to have the coelacanth included in Appendix I of CITES.
Subsequent dives by Fricke and his team with the new submersible JAGO at Grand Comoro revealed a serious decline in the number of coelacanths in each previously surveyed cave. Thus the initial estimates of the numbers of adults (200–500) became potentially invalid. In spite of the discovery of additional individuals off Sulawesi in 1998 and lately at Sodwana Bay (South Africa), the living coelacanth remains unique and highly vulnerable because of its narrow habitat range and very specialized physiology and life style. Although the 2002 IUCN Red List does not list Latimeria menadoensis, it lists L. chalumnae as Critically Endangered.
Significance to humans
Before the coelacanth's value for science was recognized in the mid-twentieth century, it was occasionally consumed for its presumed antimalarial properties. Because of its high oil content, the meat tastes foul and rancid and causes severe diarrhea when eaten. Since 1952 its interest to science has remained extremely high.
Resources
Books:Forey, P. History of the Coelacanth Fishes. London: Chapman & Hall, 1998.
Musick, J. A., M. N. Bruton, and E. K. Balon, eds. The Biology of Latimeria chalumnae and Evolution of Coelacanths. Dordrecht: Kluwer Academic Publishers, 1991.
Smith, J. L. B. Old Fourlegs: The Story of the Coelacanth. London: Readers Union, Longmans, Green, 1957.
Thomson, K. S. Living Fossil: The Story of the Coelacanth. New York: W.W. Norton & Company, 1991.
Walker, S. M. Fossil Fish Found Alive: Discovering the Coelacanth. Minneapolis: Carolrhoda Books, Inc., 2002.
Weinberg, S. A. Last of the Pirates: The Search for Bob Denard. New York: Pantheon Books, 1994. ——. Fish Caught in Time: The Search for the Coelacanth. London: Fourth Estate, 1999.
Periodicals:Anthony, J., and J. Millot. "Première capture d'une femelle de coelacanthe en estat de maturité sexuelle." C.R. Acad. Sc. Paris Sér. D224 (1972): 1925–1927.
Balon, E. K. "The Living Coelacanth Endangered: A Personalized Tale." Tropical Fish Hobbyist 38 (February 1990): 117–129. ——. "Prelude: The Mystery of a Persistent Life Form." Environmental Biology of Fishes 32 (1991): 9–13. ——. "Probable Evolution of the Coelacanth's Reproductive Style: Lecithotrophy and Orally Feeding Embryos in Cichlid Fishes and in Latimeria chalumnae." Environmental Biology of Fishes 32 (1991): 249–265. ——. "Dynamics of Biodiversity and Mechanisms of Change: A Plea for Balanced Attention to Form Creation and Extinction." Biological Conservation 66 (1993): 5–16. ——. "See Also Other Recent Websites on the Coelacanth." Environmental Biological of Fishes 54 (1999): 466.
Balon, E. L., M. N. Bruton, and H. Fricke. "A Fiftieth Anniversary Reflection on the Living Coelacanth, Latimeria chalumnae: Some New Interpretations of Its Natural History and Conservation Status." Environmental Biology of Fishes 23 (1988): 241–280.
Bogart, J. P., E. K. Balon, and M. N. Bruton. "The Chromosomes of the Living Coelacanth and Their Remarkable Similarity to Those of One of the Most Ancient Frogs." Journal of Heredity 85 (1994): 322–325.
Bruton, M. N., A. J. P. Cabral, and H. W. Fricke. "First Capture of a Coelacanth, Latimeria chalumnae (Pisces, Latimeriidae), Off Mozambique." South African Journal of Science 88 (1992): 225–227.
Erdmann, M. V. "An Account of the First Living Coelacanth Known to Scientists from Indonesian Waters." Environmental Biology of Fishes 54 (1999): 439–443.
Erdmann, M. V., and R. L. Caldwell. "How New Technology Put a Coelacanth Among the Heirs of Piltdown Man." Nature 406 (2000): 343.
Erdmann, M. V., R. L. Caldwell, S. L. Jewett, and A. Tjakrawidjaja. "The Second Recorded Living Coelacanth from North Sulawesi." Environmental Biology of Fishes 54(1999): 445–451.
Erdmann, M. V., R. L. Caldwell, and M. Kasim Moosa. "Indonesian 'King of the Sea' Discovered." Nature 395(1998): 335.
Fricke, H. W., and J. Frahm. "Evidence for Lecithotrophic Viviparity in the Living Coelacanth." Naturwissenschaften 79(1992): 476–479.
Fricke, H. W., and K. Hissman. "Natural Habitat of Coelacanths." Nature 346 (1990): 323–324. ——. "Locomotion, Fin Coordination and Body of the Living Coelacanth Latimeria chalumnae." Environmental Biology of Fishes 34 (1992): 329–356. ——. "Home Range and Migrations of the Living Coelacanth Latimeria chalumnae." Marine Biology 120 (1994): 171–180.
Fricke, H. W., K. Hissman, J. Schauer, O. Reinicke, and R. Plante. "Habitat and Population Size of the Coelacanth Latimeria chalumnae at Grande Comore." Environmental Biology of Fishes 32 (1991): 287–300.
Fricke, H. W., and R. Plante. "Habitat Requirements of the Living Coelacanth Latimeria chalumnae at Grande Comore, Indian Ocean." Naturwissenschaften 75 (1988): 149–151.
Fricke, H. W., O. Reinicke, H. Hofer, and W. Nachtigall. "Locomotion of the Coelacanth Latimeria chalumnae in Its Natural Environment." Nature 329 (1987): 331–333.
Fricke, H. W., J. Schauer, K. Hissmann, L. Kasang, and R. Plante. "Coelacanths Aggregate in Caves: First Observations on Their Resting Habitat and Social Behavior." Environmental Biology of Fishes 30 (1991): 282–285.
Gorr, T., T. Kleinschmidt, and H. W. Fricke. "Close Tetrapod Relationships of the Coelacanth Latimeria Initiated by Hemoglobin Sequences." Nature 351 (1991): 394–397.
Hensel, K., and E. K. Balon. "The Sensory Canal System of the Living Coelacanth, Latimeria chalumnae: A New Installment." Environmental Biology of Fishes 61 (2001): 117–124.
Hissmann, K., and H. W. Fricke. "Movements of the Epicaudal Fin in Coelacanths." Copeia 1996: 605–615.
Hissmann, K., H. W. Fricke, and J. Schauer. "Population
Monitoring of a Living Fossil: The Coelacanth Latimeria chalumnae in Decline?" Conservation Biology 12 (1998): 759–765.
Holder, M. T., M. V. Erdmann, T. P. Wilcox, R. L. Caldwell, and D. M. Hillis. "Two Living Species of Coelacanths?" Proceedings of the National Academy of Sciences U.S.A. 96(1999): 12616–12620.
McCabe, H. "Recriminations and Confusion over the 'Fake' Coelacanth Photo." Nature 406 (2000): 225.
McCabe, H., and J. Wright. "Tangled Tale of a Lost, Stolen and Disputed Coelacanth." Nature 406 (2000): 114.
Pouyaud, L., S. Wirjoatmodjo, I. Rachmatika, A. Tjakrawidjaja, R. Hadiaty, and W. Hadie. "Une nouvelle espèce de coelacanthe. Preuves génétiques et morphologiques." C.R. Acad. Sci. Paris, Sciences de la vie 322 (1999): 261–267.
Springer, V. G. "Are the Indonesian and Western Indian Ocean Coelacanths Conspecific: A Prediction." Environmental Biology of Fishes 54 (1999): 453–456.
Suzuki, N., Y. Suyehiro, and T. Hamada. "Initial Report of Expeditions for Coelacanth, Part I, Field Studies in 1981 and 1983." Scientific Papers of the College of Arts and Sciences, Univ. Tokyo 35 (1985): 37–79.
Wourms, J. P., J. W. Atz, and M. D. Stribling. "Viviparity and the Maternal-embryonic Relationship in the Coelacanth Latimeria chalumnae." Environmental Biology of Fishes 32 (1991): 225–248.
Organizations:South African Coelacanth Conservation and Genome Resource Programme. South African Institute for Aquatic Biodiversity, Somerset Street, Private Bag 1015, Grahamstown, 6140 South Africa. Phone: +27 (0)46 636 1002. Fax: +27 (0)46 6222403. Web site:
Other:"Coelacanth Conservation Council/Conseil pour la Conservation du Coelacanthe Newsletter, No. 1." Environmental Biology of Fishes 23 (1988): 315–319 "Coelacanth Conservation Council/Conseil pour la Conservation du Coelacanthe Newsletter, No. 2." Environmental Biology of Fishes 30 (1991): 423–428. "Coelacanth Conservation Council/Conseil pour la Conservation du Coelacanthe Newsletter, No. 3." Environmental Biology of Fishes 33 (1992): 413–417. "Coelacanth Conservation Council/Conseil pour la Conservation du Coelacanthe Newsletter, No. 4." Environmental Biology of Fishes 36 (1993): 395–406. "Coelacanth Conservation Council/Conseil pour la Conservation du Coelacanthe Newsletter, No. 5." Environmental Biology of Fishes 38 (1993): 399–410. "Coelacanth Conservation Council/Conseil pour la Conservation du Coelacanthe Newsletter, No. 6." Environmental Biology of Fishes 54 (1999): 457–469.
[Article by: Eugene K. Balon, PhD]
For more information on coelacanth, visit Britannica.com.
The noun has one meaning:
Meaning #1:
fish thought to have been extinct since the Cretaceous Period but found in 1938 off the coast of Africa
Synonym: Latimeria chalumnae
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Coelacanth ('hollow spine' in Greek, coelia (κοιλιά) meaning
hollow and acanthos (άκανθος) spine) IPA: /ˈsiːləkænθ/ is the common name for an order of fish that includes the oldest living lineage of
Coelacanths first appear in the fossil record in the Middle Devonian, about 410 million years ago.[3] Prehistoric species of coelacanth lived in many bodies of water in Late Paleozoic and Mesozoic times.
Coelacanths are lobe-finned fish with the pectoral and anal fins on fleshy stalks supported by bones, and the tail or caudal fin diphycercal (divided into three lobes), the middle one of which also includes a continuation of the notochord. Coelacanths have modified cosmoid scales, which are thinner than true cosmoid scales, which can only be found on extinct fish. Coelacanths also have a special electroreceptive device called a rostral organ in the front of the skull, which probably helps in prey detection.
Although now represented by only two known living species, as a group the coelacanths were once very successful with many genera and species that left an abundant fossil record from the Devonian to the end of the Cretaceous period, at which point they apparently suffered a nearly complete extinction. No fossils dated after this point are known to have been found.[citation needed] It is often claimed that the coelacanth has remained unchanged for millions of years but in fact the living species and even genus are unknown from the fossil record. However, some of the extinct species, particularly those of the last known fossil coelacanth, the Cretaceous genus Macropoma, closely resemble the living species.[citation needed] The most likely reason for the gap is the taxon having become extinct in shallow waters. Deep-water fossils are only rarely lifted to levels where paleontologists can recover them, making most deep-water taxa disappear from the fossil record. This situation is still under investigation by scientists.
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The average weight of the living West Indian Ocean coelacanth, Latimeria chalumnae, is 80kg (176 pounds), and they can reach up to 2m (6.5 feet) in length. Adult females are slightly larger than males. Based on growth rings in their ear bones (otoliths), scientists infer that individual coelacanths may live as long as 80 to 100 years. Coelacanths live as deep as 700 m (2300ft) below sea level, but are more usually found at depths of 90 to 200 m. Living examples of Latimeria chalumnae have a deep blue color which probably camouflages them from prey species; however, the Indonesian species is brown. Latimeria chalumnae is widely but very sparsely distributed around the rim of the western Indian Ocean, seemingly occurring in small colonies. Coelacanth eyes are very sensitive, and have a tapetum lucidum. Coelacanths are almost never caught in the daytime or on nights with full moons, due to the sensitivity of their eyes. Coelacanth eyes also have many rods: tiny structures that help animals see in dim light. Together, the rods and tapetum help the fish see better in dark water.
Coelacanths are opportunistic feeders, hunting cuttlefish, squid, snipe eels, small sharks, and other fish found in their deep reef and volcanic slope habitats. Coelacanths are also known to swim head down, backwards and belly up to locate their prey, presumably utilizing its rostral gland. Scientists suspect that one reason this fish has been so successful is that they can slow down their metabolisms at will, sinking into the less-inhabited depths and minimizing their nutritional requirements in a sort of hibernation mode.
The coelacanths which live near Sodwana Bay, South Africa, rest in caves at depths of 90 to 150 m during daylight hours, but disperse and swim to depths as shallow as 55 m when hunting at night. The depth is not as important as their need for very dim light, and water which has a temperature of 14 to 22°C, and they will rise or sink to find these conditions.[citation needed]
In accordance with the Convention on International Trade of Endangered Species treaty, the coelacanth was added to Appendix I (threatened with extinction) in 1989. The treaty forbids international trade for commercial purposes and regulates all trade, including sending specimens to museums, through a system of permits. In 1998, the total coelacanth population was estimated to have been 500 or fewer, a number that would threaten the survival of the species.[4]
Female coelacanths give birth to live young, called "pups", in groups of between 5 and 25 fry at a time; the pups are capable of surviving on their own immediately after birth. Their reproductive behaviors are not well known, but it is believed that they are not sexually mature until after 20 years of age. Gestation time is 13 months.
| Date | Description |
|---|---|
| 1938 | (December 23) Discovery of the first modern coelacanth 30 kilometers SW of East London, South Africa. |
| 1952 | (December 21) Second specimen identified in the Comoros. Since then more than 200 have been caught around the islands. |
| 1988 | First photographs of coelacanths in their natural habitat, by Hans Fricke off Grand Comore. |
| 1991 | First coelacanth identified near Mozambique, 24 kilometers offshore NE of Quelimane. |
| 1995 | First recorded coelacanth on Madagascar, 30 kilometers S of Tuléar. |
| 1997 | (September 18) New species of coelacanth found in Indonesia. |
| 2000 | A group found by divers off Sodwana Bay, South Africa. |
| 2001 | A group found off the coast of Kenya. |
| 2003 | First coelacanth caught by fisherman in Tanzania. Within the year, 22 were caught in total. |
| 2004 | Canadian researcher William Sommers captured the largest recorded specimen of coelacanth off the coast of Madagascar.[citation needed] |
| 2007 | (May 19) Indonesian fisherman Justinus Lahama caught a 1.31 meter (4.30 ft) long, 51 kilogram (112 lb) coelacanth off Sulawesi Island, near Bunaken National Marine Park, that survived for 17 hours in a quarantined pool.[7] |
| 2007 | (July 15) Two fishermen from Zanzibar caught a coelacanth measuring 1.34 meters (4.40 ft), and weighing 27 kilograms (60 lb). The fish was caught off the north tip of the island, off the coast of Tanzania.[8] |
On December 23, 1938, Hendrik Goosen, the captain of the trawler Nerine returned to the harbour at East London after a trawl around the mouth of the Chalumna River. As he frequently did, he telephoned his friend, Marjorie Courtenay-Latimer, curator at East London's small museum, to see if she wanted to look over the contents of the catch for anything interesting. At the harbour, Latimer noticed a blue fin and took a closer look. There she found what she later described as "the most beautiful fish I had ever seen, five feet long, and a pale mauve blue with iridescent silver markings."
Failing to find a description of the creature in any of her books, she attempted to contact her friend, Professor James Leonard Brierley Smith, but he was away for Christmas. Unable to preserve the fish, she reluctantly sent it to a taxidermist. When Smith returned, he immediately recognized it as a coelacanth, known only from fossils. Smith named the fish Latimeria chalumnae in honor of Marjorie Courtenay-Latimer and the waters in which it was found. The two discoverers received immediate recognition, and the fish became known as a "living fossil." The 1938 coelacanth is still on display in the East London Museum.
However, as the specimen had been stuffed, the gills and skeleton were not available for examination, and some doubt therefore remained as to whether it was truly the same species. Smith began a hunt for a second specimen that would take more than a decade.
A worldwide search was launched for more coelacanths, with a reward of 100 British pounds, a very substantial sum to the average South African fisherman of the time. Fourteen years later, one specimen was found in the Comoros, but the fish was no stranger to the locals -- in the port of Mutsamudu on the Comorian island of Anjouap, the Comorians were puzzled to be so rewarded for a "gombessa" or "mame", their names for the nearly inedible fish that their fishermen occasionally caught by mistake.
The second specimen, found in 1952 by Comorian fisherman Ahamadi Abdallah, was described as a different species, first as 'Malania hunti' and later as Malania anjounae, after Daniel François Malan, the South African Prime Minister who had dispatched an SAAF Dakota at the behest of Professor Smith to fetch the specimen. It was later discovered that the lack of a first dorsal fin, at first thought to be significant, was caused by an injury early in the specimen's life. Ironically, Malan was a staunch creationist; startled by the sight of the ancient creature, he exclaimed, "Why, it's ugly! Is this where we come from?" The specimen retrieved by Smith is on display at the SAIAB in Grahamstown, South Africa where he worked.
The Comorians are now aware of the significance of the endangered species, and have established a program to return accidentally-caught coelacanth to deep water.
As for Smith, who died in 1968, his account of the coelacanth story appeared in the book Old Fourlegs, first published in 1956. His book Sea Fishes of the Indian Ocean, illustrated and co-authored by his wife Margaret, remains the standard ichthyological reference for the region.
In 1988, National Geographic photographer Hans Fricke was the first to photograph the species in its natural habitat, m ({{FORMATNUM:590 ft 61⁄2 in}}) off Grand Comore's west coast.[9]
On September 18, 1997, Arnaz and Mark Erdmann, traveling in Indonesia on their honeymoon, saw a strange fish enter the market at Manado Tua, on the island of Sulawesi.[4] Mark thought it was a gombessa (Comoros coelacanth), although it was brown, not blue. An expert noticed their pictures on the Internet and realized its significance. Subsequently, the Erdmanns contacted local fisherman and asked for any future catches of the fish to be brought to them. A second Indonesian specimen, 1.2 m in length and weighing 29 kg. was captured alive on July 30, 1998.[6] It lived for six hours, allowing scientists to photographically document its coloration, fin movements and general behavior. The specimen was preserved and donated to the Museum Zoologicum Bogoriense (MZB), part of the Indonesian Institute of Sciences (LIPI).[4]
DNA testing revealed that this specimen differed genetically from the Comorian population. Superficially, the Indonesian coelacanth, locally called raja laut ("King of the Sea"), appears to be the same as those found in the Comoros except that the background coloration of the skin is brownish-gray rather than bluish. This fish was described in a 1999 issue of Environmental Biology of Fishes by Pouyaud et al. It was given the scientific name Latimeria menadoensis. A molecular study estimated the divergence time between the two coelacanth species to be 40–30 mya.[10]
On May 19, 2007, Justinus Lahama, an Indonesian fisherman, caught a 1.3-metre-long, 50kg/110 pound coelacanth off the coast near Manado, on northern Sulawesi Island near Bunaken National Marine Park. After spending 30 minutes out of water, the fish, still alive, was placed in a netted pool in front of a restaurant at the edge of the sea. It survived for 17 hours. Coelacanths, closely related to lungfish, usually live at depths of 200-1,000 metres. The fish was filmed by local authorities swimming in the metre-deep pool, then frozen after it died. AFP claim French, Japanese and Indonesian scientists working with the French Institute for Development and Research carried out an autopsy on the coelacanth with genetic analysis to follow. The local university is now studying the carcass.[11][7]
In South Africa, the search continued on and off over the years. 46-year-old diver Riaan Bouwer lost his life searching for coelacanths in June 1998.
On the 28th of October 2000, just south of the Mozambique border in Sodwana Bay in the St. Lucia Marine Protected Area, three deep-water divers, Pieter Venter, Peter Timm, and Etienne le Roux, made a dive to 104 metres and unexpectedly spotted a coelacanth.
Calling themselves "SA Coelacanth Expedition 2000", the group returned with photographic equipment and several additional members. On the 27th of November, after an unsuccessful initial dive the previous day, four members of the group, Pieter Venter, Gilbert Gunn, Christo Serfontein, and Dennis Harding, found three coelacanths. The largest was between 1.5 and 1.8 metres in length; the other two were from 1 to 1.2 metres. The fish swam head-down and appeared to be feeding from the cavern ledges. The group returned with video footage and photographs of the coelacanths.
During the dive, however, Serfontein lost consciousness, and 34-year-old Dennis Harding rose to the surface with him in an uncontrolled ascent. Harding complained of neck pains and died from a cerebral embolism while on the boat. Serfontein recovered after being taken underwater for decompression sickness treatment.
In March–April of 2002, the Jago Submersible and Fricke Dive Team descended into the depths off Sodwana and observed fifteen coelacanths. A dart probe was used to collect tissue samples.
The shallowest recorded sighting of a coelacanth is at a depth of 58 m off the coast of Sodwana Bay by Christo Vanjaarsveld.
Coelacanths have been caught off the coast of Tanzania since 2004. Two coelacanths were initially reported captured in Kigombe, a small village off the edge of the Indian Ocean in August 2004. A spate of 19 more specimens of these extremely rare fishes weighing between 25 kg. to 80 kg. were reported netted in the space of the next 5 months, with another specimen captured in January 2005. A coelacanth weighing as much as 110 kg. was reported by the Observer newspaper in 2006. Officials of the Tanga Coastal Zone Conservation and Development Programme, which has a long-term strategy for protecting the species, see a connection with the timing of the captures with trawling - especially by Japanese vessels - near the coelacanth's habitat, as within a couple of days of trawlers casting their nets coelacanths have turned up in shallow-water fishing nets intended for sharks. The sudden appearance of the coelacanth off Tanzania that has raised real worries about its future due to damage done to the coelacanth population by the effects of indiscriminate trawling methods and habitat damage.[12]
Hassan Kolombo, a programme co-ordinator, said. "Once we do not have trawlers, we don't get the coelacanths, it's as simple as that." His colleague, Solomon Makoloweka, said they had been pressuring the Tanzanian government to limit trawlers' activities. He said: "I suppose we should be grateful to these trawlers, because they have revealed this amazing and unique fish population. but we are concerned they could destroy these precious things. We want the government to limit their activity and to help fund a proper research programme so that we can learn more about the coelacanths and protect them."[12]
Subclass Coelacanthimorpha (Actinistia) are sometimes used to designate the group of Sarcopterygian fish that contains the Coelacanthiformes. The following is a classification of known coelacanth genera and families:[6]
Class Sarcopterygii
Subclass Coelacanthimorpha
The coelacanths' widely-published status as a "living fossil" caught the popular imagination to the extent that the coelacanth figures in popular culture. The fish figures in numerous video games and various media.
