Coelacanths

Scientific classification of the Coelacanth species

Kingdom: Animalia
Phylum: Chordata
Class: Sarcopterygii
Order: Coelacanthiformes
Family: Latimeriidae
Genus: Latimeria

Coelacanths are bony fishes from the order Coelacanthiformes. There exists two known Latimeria species today: Latimeria chalumnae (Comores) and Latimeria menadoensis (North Sulawesi). Their morphology is very similar, but they have been declared two separated species based on DNA tests. Their coloration differs, and the Latimeria chalumnae is blue with pinkish white blotches, while the Latimeria menadoensis is brown with pinkish white blotches and golden flecks. These blotch patterns are unique to each individual and make it possible for scientists to distinguish one Coelacanths specimen from another.

Common names for the Coelacanths

Afrikaans: Seelakant
American English: Latimeria, Old Four Legs
English: Coelacanth, Gombessa
Finnish: Latimeria
French: Coelacanthe
Indonesian: Raja laut
Polish: Latimeria
Spanish: Celecanto
Swedish: Kvastfening, Tofsstjärtfisk

The early history of the Coelacanths

The Coelacanths belong to the oldest lineage of fish currently known to science. The oldest found Coelacanth fossils imply that the Coelacanth fish species developed around 400.000.000 years ago during the Devonian period. At the end of the Cretaceous period, 65.000.000 years ago, these species almost completely disappeared from the planet. This extinction took place simultaneously with another much more famous extinction; the disappearance of the dinosaurs. The Coelacanths were long believed to have been completely extinct during the end of the Cretaceous period, but today we know about two Coelacanth species that have survived into our time. Since the Coelacanths live deep down in the ocean, we might encounter even more species in the future.

Before the end of the Cretaceous period, the oceans were filled with a wide range of different Coelacanth species. Today, both living Coelacanth species are found within one single genus, the Latimeria. Interestingly enough, we have still not found any fossilized specimens from the genus Latimeria; all the described fossils belong to other genera. No Coelacanth fossils have been found from specimens living after the Devonian and Cretaceous period. The fossils most similar to Latimeria chalumnae and Latimeria menadoensis dates back to the end of the Cretaceous period and have been formed from Coelacanth species within the genus Macropoma. In a majority of the known Coelacanth fossils, the swim bladder seems to be bony (ossified) which means that these fishes most likely lived in quite shallow waters. The modern Coelacanths are however known to inhabit great depths and have been found as far down as 700 meters (0.4 miles)

Modern history

The first description of a Coelacanth fossil is found in the book “Poissons Fossiles” which was published by Louis Agassiz in 1836. Agassiz called the fish Coelacanthus due to the hollow spines that goes from the vertebrae to the caudal fin rays. The term Coelacanthus is formed by combining two Greek words and can be translated into “hollow thorn”, or more freely “spacious spine”. It is pronounced seel-uh-kanth in English and selakant in Afrikaans.

As mentioned above, the Coelacanths used to be considered extinct since we only knew of them from fossils. In 1938, a live specimen was however found in South Africa, and since this first discovery Coelacanths have been found in other countries as well, including Comoros, Kenya, Mozambique, Tanzania, Madagascar, and Indonesia.

The first Coelacanth finding

The first living Coelacanth was discovered by a museum curator named Marjorie Courtenay-Latimer. She began her work as a curator of the new East London Museum in East London, South Africa in 1930. Her work was focused on the natural history of the Eastern Cape. The museum already had a small collection of bird specimens when she was appointed curator, but Courtenay-Latimer decided that she wanted to include marine life in the exhibitions as well, since fishing was an important industry in the region. Courtenay-Latimer encouraged fishing clubs and fishing trawlers to donate marine specimens to the museum and the collection grew rapidly. In 1936, she befriended Hendrik Goosen, the captain of a trawler named Nerine. Goosen began to save interesting marine specimens and bring them back to East London, where Courtenay-Latimer could include them in the museum's collection.

On December 22, 1938, the trawler Nerine reached the East London harbor carrying several unusual fishes. Since Goosen new of Courtenay-Latimer's fascination for strange marine creatures, he contacted the museum and said that he had several specimens onboard that she might want to take a look at. Courtenay-Latimer was actually very busy preparing fossil reptile bones from Tarkastad at the time, but since it was only a few days before Christmas she decided to go to the harbor anyway and wish the captain and his crew a Merry Christmas.

When Courtenay-Latimer took a look at the fish onboard the Nerine, a blue color caught her attention and she found a strange looking 150 centimeter / 4.9 feet long fish, and by the look of it Courtenay-Latimer realized that it had to be a very primitive fish type. The scales of the fish were hard and bony and equipped with thorn-like spines. The fins were paired and almost resembled small legs. That fish had been caught approximately 70 meters / 77 yards from the mouth of the Chalumna River, in the Indian Ocean. Courtenay-Latimer managed to convince a taxi driver to carry the big fish (it weighed 57.5 kg /127 lbs) in the trunk of his car and deliver it to the museum.

The East London climate was extremely hot around Christmas, and preserving the fish until it could be properly described and classified turned out to be a major problem. Courtenay-Latimer actually tried to make the morgue accept the fish, but they denied her request. Experts claimed that preserving the fish was a waste of time, since it was just a rock cod of no interest to science. Fortunately, Courtenay-Latimer refused to listen to them and decided to preserve the fish herself. Since it was too large to fit into a bath, she soaked cloths in formalin and wrapped around it. On the 26th of December, a taxidermist skinned the fish and unfortunately the internal organs were not preserved.

Courtenay-Latimer then decided to contact a friend of her, James Leonard BrierleySmith, who was a lecturer in Chemistry at Rhodes University College. He was also an autodidact ichthyologist with a special interest in South African marine fish species. He and Courtenay-Latimer had know each other since 1933, when he had visited her museum and offered her to help her classify fish specimens since the museum did not own any books on the subject. Soon after her finding, Courtenay-Latimer wrote a letter to him describing the strange fish, and she also included the brief sketch that would later become known among scientists world wide.

When James Leonard BrierleySmith received the letter, he immediately realized that the sketch shared an uncanny resemblance to a type of fish that was believed to have been extinct at the end of the Cretaceous period, 65.000.000 years ago. He ordered a copy of Arthur Smith Woodward's Catalogue of Fossil Fishes of the British Museum, and used the book to identify the fish as a Coelacanth. He later traveled to the East London Museum and examined the preserved specimen, before naming it Latimeria chalumnae. The first part of the name is in honor of Courtenay-Latimer, while the second part is derived from the Chalumna River near which the fish was caught.

Smith and his wife Margaret spent the initial half of 1939 writing the first scientific paper describing the fish. Only four days after finally finishing the paper, Margaret gave birth to their son William. The fish was returned from the Smith couple to the East London Museum where it was put on display and attracted thousands of visitors.

The second Coelacanth finding

Despite vigorous efforts to capture more Coelacanths, it would take 14 years before another specimen was found. Interestingly enough, this fish was also found at Christmas time. James Leonard BrierleySmith had offered 100 British pounds to anyone who could bring him another Coelacanth. He and his wife had also embarked on expeditions to Kenya, Mozambique, Tanganyika and Zanzibar where they had collected fish and spread the word about the remarkable Coelacanths. When the Smith couple was in Zanzibar, they met a young man named Eric Hunt. He was the captain of a small trading schooner which trafficked the waters between the mainland and the Comoro archipelago. Hunt offered to bring posters of the Coelacanths to the Comoro archipelago, and let people there know about the reward.

The Coelacanths were actually already well known among the Comoro fishermen, and they even had a name for the fish – Gombessa. Hunt did however not know about this, and he himself had never encountered a Gombessa.

On December 24th, 1952, the Smiths received a telegram from Hunt. The telegram told them that a 5 feet (1.5 meters) long Coelacanth had been caught off Anjouan Island on the 20th. It was now in Hunt's possession and had been injected with formalin. The telegram had been sent from Dzaoudzi at Mayotte to Grahamstown, and then forwarded to the ship Dunnottar Castle when it reached Durban. The Smiths did not really know exactly where Dzaoudzi was located, but they understood that the specimen had been landed on French territory and that the French might very well confiscate it. The fish did however manage to reach the Comoros without being seized by the French, from where the Smiths could retrieve it on December 28th.

This Coelacanth had been caught in deep water, approximately 200 meters from shore. It had been landed on a local market where a schoolteacher spotted it and understood that it was the fish from the poster. The fisherman and his companions brought the huge fish to Hunt, and this must have been quite an unpleasant journey since they traveled 40 kilometers (25 miles) overland with a huge, dead fish under the hot African sun. Hunt had previously asked Margaret Smith about the best way to preserve a Coelacanth without using a refrigerator, and she had told him to use salt if he ever came across the fish. When the Coelacanth was brought to Hunt by Hasten, Hunt therefore slit it and salted it in order to preserve it. Later, a French medical officer on Mayotte used up his entire formalin stash in order to preserve the fish even better. The Coelacanth was then draped in cotton and placed in a crate made from kapok tree.

The Smiths managed to reach Comoros on December 28th, in a ship that had been lent to them by the South African Prime Minister D F Malan. The Coelacanth was brought back to South Africa and the fisherman was of course paid the finders fee. When Smith examined the fish, he noticed that it had not first dorsal fin and he therefore assumed that it belonged to another genus than the Latimeria chalumnae. He wanted to name it Malania hunti, but Hunt protested since he was afraid that the French might no like that he had let a rare fish escape from French waters into South Africa. He suggested that the species should be named after the island off which it had been caught by the fishermen, and Smith therefore named it Malania anjounae. The first part of the name, Malania, was in honor of South African Prime Minister D F Malan. Later, it turned out that this specimen was actually another Latimeria chalumnae – the first dorsal fin was lacking due to an old injury. Just like the first caught Latimeria chalumnae, the specimen was a male.

Later Coelacanth findings

The reward offered by Smith eventually resulted in a collection of more then 150 Coelacanths from the Comoros. A majority of these fishes were however kept by the French, and during the following 15 years no foreign scientists were allowed to search the waters of the Comoros. Dr Jacques Millot was in charge of one of the largest Coelacanth projects, and his team eventually published three large volumes regarding the anatomy of the Coelacanths, together with several papers.

Other notable research efforts include the filming of a Coelacanth in its natural habitat. This project was carried out by German scientist Prof. Hans Fricke of the Max Planck Institute using a two-man submersible. During a later expedition, Fricke's research team encountered several Coelacanths that shared a cave, and they also noted that Coelacanths can live as far down as 700 meters (0.4 miles).

In 1991, Mike Bruton and Sheila Coutouvidis created a comprehensive list of all known Latimeria chalumnaespecimens. This list shows that at least 191 Coelacanths have been caught, but a lot of specimens do leave the Comoros without first being described and documented by scientists. The list is based on scientific writings and aquarium, museum and university holdings. Bruton and Coutouvidis also gave each known specimen an identifying number to simplify further research, and the list includes biological details when known.

Coelacanth look and anatomy

How big is the Coelacanth?

A fully grown Coelacanth can be 180 centimeters / 5.9 feet or longer and weigh 98 kg / 216 lbs. Since we still only know of a few

The notochord

The Coelacanth fishes have several interesting anatomical features. The name Coelacanth is derived from two Greek words: “coelia” which means hollow and “acanthos” which means thorn. The term Coelacanth can therefore be translated into hollow thorn, and this has to do with the so called notochord found in Coelacanths. Most fish species have a bony vertebral column as adults, but the Coelacanths are instead equipped with a large and wide tube of cartilage called a notochord. Normally, fish embryos and larvae have a notochord, but this cartilage structure is then gradually turned into a segmented bony/calcified vertebral column as the fish grows older. Coelacanths will however keep their notochord for their entire life. They share this characteristic with two other very old fish groups: the lungfishes and the primitive sharks. In the Coelacanths, this hollow notochord is filled with oil. Even though it is not a bony/calcified structure, it is very strong and manages to support and protect the spinal cord.

The fins

Another distinguishing and easily observed anatomical feature seen only in Coelacanths is the unusual fins. The tail fin has a lanceolate shape. It is has several rays in the upper and lower margins, and a small central supplementary fin is located beyond the fin margin. The first dorsal fin is fan shaped and supported by a single bony plate. The Coelacanths are also equipped with fleshy pectoral, pelvic, anal and second dorsal fins. The skeletal parts in the anal fin and second dorsal fin look exactly the same. All and all, the Coelacanth fish have eight fins – 2 dorsal fins, 2 pectoral fins, 2 pelvic fins, 1 anal fin and 1 caudal fin.

The Coelacanths belong to a group of fishes known as lobe-finned. This group is very small compared to the dominant vertebrate group; the ray-finned fishes. The lobed-finned and the ray-finned fishes make up two different evolutionary lines, and the amphibians trace their ancestry back to the lobe-finned fishes. As mentioned above, the Coelacanth has two dorsal fins, and this distinguishes it from most ray-finned fishes since they typically have only one dorsal fins. (Sharks and rays are however exceptions to this rule.)

The brain

The brain of the Coelacanth does not grow much once the fish has been born. This means that the size of the brain will stay the same even when the size of the head and body increases significantly as the fish matures. A Coelacanth brain is not very convoluted and takes up no more than 2 percent of the cranial cavity in adult specimens. You will find the brain of the Coelacanth at the rear part of the cranium, and this might have something to do with the electro-receptive rostral organ that can be found in the snout of the fish. Perhaps a brain located as far back as possible causes less electrical interference with the rostral organ. Similar configurations can be seen in a few other fish species, such a the Sixgill stingray (Hexatrygon bickelli).

Coelacanth reproduction

The Coelacanth is a so called ovoviviparous fish. The eggs are fertilized while still inside the female fish, and the foetuses develop inside her until they are large enough to be born. In the known Coelacanth species, the pups will be born when they have reached a size of roughly 35 centimeters (14 inches). The eggs are actually larger than the eggs of any other fish species and can have a diameter of 9 centimeters (3.5 inches) while weighing over 325 g (0. 7lbs).

Earlier, scientists believed that the foetuses practised cannibalism, but this is not the case. Neither do they feed on the large egg-yolks before they are born. The gestation period for the Latimeria species is probably around 13 months, but more research is necessary since we still know very little about Coelacanth reproduction.

Other interesting facts about the Coelacanth

• The lobed fins found on the Coelacanth are remarkably mobile. This fish can rotate its fins through 100 degrees, and since the lobes are fleshy each of the fins can be used like a small paddle.
  

• The Coelacanth is equipped with an electro-receptive rostral organ that can be used to locate prey at the bottom of the sea. The rostral organ is found in the snout and is connected to three tubes that surface on each side of the snout.
  

• A frightened Coelacanth will use its big caudal fin to make a quick escape, but most of the time this fish swims around very leisurely.
  

• The paired lobed fins might look like tiny legs, but as far as we know the Coelacanth never uses them to “walk” on the bottom of the ocean. It is true that this fish like to spend a lot of time near the sea bottom, but it prefers to stay slightly above the bottom and never touch it with its fins. A Lungfish sometimes uses its fins to prop its body off the sea bed, but this behavior is not known among Coelacanths.
  

• The Coelacanth can position itself in a fascination posture by keeping its mouth near the bottom while the body is placed in an upright position with the tailfin pointing towards the surface.
  

• Most bony fishes have their swim bladder filled with gas, but the Coelacanth will instead use fat to fill up its swim bladder. Since fat has a lower density than water, it will provide buoyancy just like a gas filled swim bladder would. The Coelacanth also has unusually high amounts of fat stored in muscle tissue, in the liver and in the cells under the skin.
  

• The Coelacanth has a cranium with a moveable front part. This mobility makes it possible for the Coelacanth to open its mouth very widely; a feature which might be helpful when feeding. The jaw of the Coelacanth is also exceptional, since the lower jaw is attached to each side of the head by means of tandem joints. There is no real upper jaw or maxillary, only an undersized median rostropremaxilla bone. Instead of a normal upper jaw, the Coelacanth is instead equipped with toothed bones at the front of the palate.

• The auricle, ventricle and conus arteriosus are arranged in a straight line in the heart of the Coelacanth. This arrangement makes the heart of the Coelacanth is an example of one of the most primitive heart-constructions found in any adult vertebrate.
  

• The Coelacanth might be the ancestor of all the four legged amphibians. In most other fish species, the nostrils are simple cups used only as olfactory organs. In the Coelacanth, the nostrils are however linked to the mouth cavity and the fish can therefore use them to breath. Another interesting feature is the fact that the pectoral and ventral fins of this fish looks almost like four simple legs.

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