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The West Indian Ocean coelacanth (''Latimeria chalumnae'') (sometimes known as gombessa, African coelacanth, or simply coelacanth) is a crossopterygian, one of two extant species of
coelacanth The coelacanths ( ) are fish belonging to the order Actinistia that includes two extant species in the genus ''Latimeria'': the West Indian Ocean coelacanth (''Latimeria chalumnae''), primarily found near the Comoro Islands off the east coast ...
, a rare order of
vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () (chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...
more closely related to
lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...
and
tetrapods Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct therapsi ...
than to the common ray-finned fishes. The other extant species is the Indonesian coelacanth (''L. menadoensis''). The West Indian Ocean coelacanth was historically known by fishermen around the Comoro Islands (where it is known as ''gombessa''), Madagascar, and Mozambique in the western Indian Ocean, but first scientifically recognised from a specimen collected in South Africa in 1938. This coelacanth was once thought to be evolutionarily conservative, but discoveries have shown initial morphological diversity. It has a vivid blue pigment, and is the better known of the two extant species. The species has been assessed as critically endangered on the
IUCN Red List The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, also known as the IUCN Red List or Red Data Book, founded in 1964, is the world's most comprehensive inventory of the global conservation status of biolo ...
.


Anatomy and physiology

The average weight of ''Latimeria chalumnae'' is 80 kg (176 lb), and they can reach up to 2 m (6.5 ft) in length. Adult females are slightly larger than males. ''Latimeria chalumnae'' exhibit a deep royal blue color with spots used as a camouflage tactic for hunting prey. Similar anatomical adaptations include the abundance of visual cells such as rods to help see when light is limited. This combined with the West Indian Ocean coelacanth's large eyes aid seeing in dark water. Similar to cartilaginous fish, ''Latimeria chalumnae'' has a rectal gland, pituitary gland, pancreas, and spinal cord. To balance osmotic pressure, these fish adopt an efficient mechanism of osmoregulation by retaining urea in their blood. ''Latimeria chalumnae'' are an ovoviviparous species, which means that they retain their eggs internally until they hatch. They also have low fecundity due to their long gestation period of around 12 months, though not much is known about their age of sexual maturity.


Habitat and behavior

''L. chalumnae'' are usually found between of depth, but are sometimes found as deep as and as shallow as . ''L. chalumnae'' tend to reside in underwater caves, which are most common at these depths. This may limit their maximum depth range, along with lack of prey. They are known to spend the daytime within these lava caves, likely for protection from predators, and use the surrounding feeding grounds at night. Coelacanths are opportunistic in their feeding. Some of their known prey species are fish that include: '' Coranthus polyacanthus'', ''
Beryx splendens The splendid alfonsino (''Beryx splendens'') is an alfonsino of the genus ''Beryx'', found around the world at depths between , usually between . Although its most common size is , it can reach lengths of up to . It is known as'' kinmedai'' (金� ...
'', '' Lucigadus ori'' and ''
Brotula multibarbata ''Brotula barbata'', commonly known as the goatsbeard brotula, is a species of cusk-eel in the genus '' Brotula''. It lives in the Indo-Pacific, in depths of up to 300 meters. It is dark brown with a submarginal black band and narrow white borde ...
''. Their intracranial joint and associated basicranial muscle likely play an important but unresolved role in feeding. Some individuals have been seen performing "headstands" as feeding behavior, allowing coelacanth to slurp prey from crevices within lava caves. This behavior is made possible due to the coelacanth's ability to move both its upper and lower jaw, which is a unique trait in extant vertebrates that have bone skeletons.


Population and conservation

''L. chalumnae'' is widely but very sparsely distributed around the rim of the western
Indian Ocean The Indian Ocean is the third-largest of the world's five oceanic divisions, covering or ~19.8% of the water on Earth's surface. It is bounded by Asia to the north, Africa to the west and Australia to the east. To the south it is bounded by ...
, from South Africa northward along the east African coast to Kenya, the Comoros and Madagascar, seemingly occurring in small colonies. In 1991, it was estimated that 2-5 coelacanths were accidentally caught each year from Grand Camoro, making up about 1% of its population. Between 1991 and 1994, there was an estimated 30% total population reduction of the coelacanth. In 1998, the total population of the West Indian Ocean coelacanth was estimated to have been 500 or fewer, a number that would threaten the survival of the species. Near Grand Comoro, an island northwest of Madagascar, a maximum of 370 individuals reside. ''L. chalumnae'' is listed as critically endangered by
IUCN The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...
. 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.


Discovery


First discovery in South Africa

On December 23, 1938, Hendrik Goosen, the captain of the trawler ''Nerine'', returned to the harbour at
East London, South Africa East London ( xh, eMonti; af, Oos-Londen) is a city on the southeast coast of South Africa in the Buffalo City Metropolitan Municipality of the Eastern Cape province. The city lies on the Indian Ocean coast, largely between the Buffalo River ...
, after a trawl between the Chalumna and Ncera Rivers. As he frequently did, he telephoned his friend, Marjorie Courtenay-Latimer, curator at East London Museum, to see if she wanted to look over the contents of the catch for anything interesting, and told her of the strange fish he had set aside for her. Correspondence in the archives of the South African Institute for Aquatic Biodiversity (SAIAB, formerly the JLB Smith Institute of Ichthyology) show that Goosen went to great lengths to avoid any damage to this fish and ordered his crew to set it aside for the East London Museum. Goosen later told how the fish was steely blue when first seen but by the time the ''Nerine'' entered East London harbour many hours later the fish had become dark grey. Failing to find a description of the creature in any of her books, she attempted to contact her friend, Professor J. L. B. Smith, but he was away for Christmas. Unable to preserve the fish, she reluctantly sent it to a
taxidermist Taxidermy is the art of preserving an animal's body via mounting (over an armature) or stuffing, for the purpose of display or study. Animals are often, but not always, portrayed in a lifelike state. The word ''taxidermy'' describes the proc ...
. When Smith returned, he immediately recognized it as a coelacanth, known to science 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 A living fossil is an extant taxon that cosmetically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living foss ...
". The 1938 coelacanth is still on display in the
East London, South Africa East London ( xh, eMonti; af, Oos-Londen) is a city on the southeast coast of South Africa in the Buffalo City Metropolitan Municipality of the Eastern Cape province. The city lies on the Indian Ocean coast, largely between the Buffalo River ...
, museum. However, as the specimen had been stuffed, the
gill A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they ar ...
s and
skeleton A skeleton is the structural frame that supports the body of an animal. There are several types of skeletons, including the exoskeleton, which is the stable outer shell of an organism, the endoskeleton, which forms the support structure inside ...
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. The West Indian Ocean coelacanth was later found to be known to fishermen of the Grande Comore and Anjouan Islands, where it inhabits the slopes of at depths between .


The second specimen, ''Malania anjouanae''

A second specimen with a missing dorsal fin and deformed tail fin was captured in 1952 off the coast of
Anjouan Anjouan (; also known as Ndzuwani or Nzwani, and historically as Johanna or Hinzuan) is an autonomous high island in the Indian Ocean that forms part of the Union of the Comoros. Its chief town is Mutsamudu and, , its population is around 277,500 ...
(
Comoros The Comoros,, ' officially the Union of the Comoros,; ar, الاتحاد القمري ' is an independent country made up of three islands in southeastern Africa, located at the northern end of the Mozambique Channel in the Indian Ocean. It ...
). At the time it was believed to be a new species and placed in a new genus as well, ''Malania'', named in honour of the
Prime Minister of South Africa The prime minister of South Africa ( af, Eerste Minister van Suid-Afrika) was the head of government in South Africa between 1910 and 1984. History of the office The position of Prime Minister was established in 1910, when the Union of Sout ...
at the time,
Daniel François Malan Daniël François Malan (; 22 May 1874 – 7 February 1959) was a South African politician who served as the fourth prime minister of South Africa from 1948 to 1954. The National Party implemented the system of apartheid, which enforce ...
, without whose help the specimen would not have been preserved with its muscles and internal organs more or less intact. It has since been accepted as ''Latimeria chalumnae''.


Taxonomy

The West Indian Ocean coelacanth (''Latimeria chalumnae'') is allocated to the genus ''Latimeria'', which it shares with one other species, the Indonesian coelacanth (''Latimeria menadoensis''). From September 1997-July 1998, two coelacanth fish were discovered off the coast of Manado Tua Island, Sulawesi, Indonesia, different from the ''Latimeria chalumnae'' discovered near the Comores. The Indonesian coelacanth is identifiable by its brownish grey color.


Genetics

The
genome In the fields of molecular biology and genetics, a genome is all the genetic information of an organism. It consists of nucleotide sequences of DNA (or RNA in RNA viruses). The nuclear genome includes protein-coding genes and non-coding ...
of ''Latimeria chalumnae'' was sequenced in 2013 to provide insight into tetrapod evolution. The coelacanths were long believed to be the closest relatives to the first tetrapods on land due to their body characteristics. However, genetic sequencing proved that the
lungfish Lungfish are freshwater vertebrates belonging to the order Dipnoi. Lungfish are best known for retaining ancestral characteristics within the Osteichthyes, including the ability to breathe air, and ancestral structures within Sarcopterygii, i ...
es are in fact the closest relatives to land tetrapods. The full sequence and annotation of the entry is available on the
Ensembl Ensembl genome database project is a scientific project at the European Bioinformatics Institute, which provides a centralized resource for geneticists, molecular biologists and other researchers studying the genomes of our own species and other v ...
genome browser.


See also

* Indonesian coelacanth (''Latimeria menadoensis'')


References


External links

* View th
West Indian Ocean coelacanth genome
in
Ensembl Ensembl genome database project is a scientific project at the European Bioinformatics Institute, which provides a centralized resource for geneticists, molecular biologists and other researchers studying the genomes of our own species and other v ...

''A Fish for Our Time''
in Intelligent Life, November/December 2013, by Samantha Weinberg * {{Taxonbar, from=Q668921 West Indian Ocean coelacanth Fish of the Indian Ocean Marine fauna of East Africa Fish of the Comoros Fish of Kenya Fish of Madagascar Fish of Mozambique Fish of Tanzania Marine fish of South Africa Critically endangered fish Critically endangered fauna of Africa West Indian Ocean coelacanth