Coelacanths, Coelacanths (Coelacanthiformes)

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Coelacanths, Coelacanths (Coelacanthiformes)
Coelacanths, Coelacanths (Coelacanthiformes)

Video: Coelacanths, Coelacanths (Coelacanthiformes)

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Video: Finding the Coelacanth | DinoFish 2023, February
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Coelacanthus belong to the ancient superorder Kistepery fish.A significant part of the species included in this order has already become extinct and is found only in the form of fossils, with the exception of representatives of the genus Latimeria. The representatives of this order, apparently, have isolated themselves from the primitive ripidists. In the early coelacanths, two large ossifications formed the cerebral skull, in the later ones, only individual ossifications developed and cartilage was preserved. Today living coelacanthous are classified as "living fossils", they are one of the oldest living creatures on Earth. Joan is missing. The coelacanthoids developed in fresh water bodies, and by the end of the Paleozoic they were widely spread over the seas. Later, their numbers and diversity decreased. Apparently, the effect of ray-finned fishes, which in the Triassic spread throughout all aquatic biotopes and began their successful development, had an effect. In the Jurassic and Cretaceous, remains of coelacanths are still found,but were not found in later layers. Therefore, they were considered a completely extinct group.

Head of coelacanth (Latimeria chalumnae), photo photograph of ancient fish
Head of coelacanth (Latimeria chalumnae), photo photograph of ancient fish

Coelacanth (Latimeria chalumnae)

Like other cross-finned fish, coelacanthoids have fins with a muscular blade at the base. The tail is dificircal, with an additional middle lobe. Fins with strong but rather short bases and elongated lobes. The role of a firm spine in coelacanths is played by an elastic tube with thick walls. The role of the cerebral skull in coelacanthus is played by a special cerebral box of two halves articulated with an internal joint on the basicranial muscle. The swim bladder, like the lungs of lungfish, departs from the ventral side of the initial part of the esophagus, is noticeably reduced and looks like a tube 5-8 cm long, passing into a band surrounded by fat.

Comorian coelacanth, or coelacanth (Latimeria chalumnae), photo photograph of ancient fish
Comorian coelacanth, or coelacanth (Latimeria chalumnae), photo photograph of ancient fish

Coelacanth (Latimeria chalumnae)

The only surviving representatives of the Celacanthus order - coelacanths - are blue-gray in color, Indonesian type - brown. In 1938, an unknown fish was caught off the coast of South Africa, which the zoologist J.L.B. Smith identified as coelacanth and named Latimeria chalumnae (in honor of the curator of the Courtenay-Latimer Museum, who discovered the fish in the catch of a minesweeper; the specific name was given by the Halumne River, near the mouth of which she was caught). It turned out that coelacanths live in the waters off the Comoros (northern part of the Mozambique Strait, between Madagascar and Africa) at depths of up to 300 m.On their head, body, including the base of the fins, there are large gray-white spots, the pattern of which is unique for each fish. These spots look like tunicates - living organisms from underwater caves in which coelacanths live, that is, a specific color masks these fish.

Comorian coelacanth, or coelacanth (Latimeria chalumnae), drawing picture
Comorian coelacanth, or coelacanth (Latimeria chalumnae), drawing picture

Coelacanth (Latimeria chalumnae)

The length of coelacanth females reaches 190 centimeters, males - 150 centimeters. The weight of these fish is 50-90 kilograms. The length of the newly born coelacanth is in the range of 35-38 cm. The powerful tail allows you to make sharp throws at the approaching prey, and the strong movable paired fins help crawl among the stones at the bottom. The spiral valve is well developed in the intestine, and the arterial cone in the heart. In a sexually mature female weighing 78 kg, 19 eggs with a diameter of 8-9 cm and weighing about 300 g each were found in the right ovary (left rudimentary); ovoviviparous.

Indonesian coelacanth (Latimeria menadoensis), drawing picture
Indonesian coelacanth (Latimeria menadoensis), drawing picture

Indonesian coelacanth (Latimeria menadoensis). © Smithsonian National Museum of Natural History

A well-developed notochord has a thick, dense and elastic fibrous sheath. The cerebral skull consists of two sections, connected to each other by a kind of joint. The brain occupies no more than the volume of the cerebral box, filled mainly with a fat-like mass.

Comoros coelacanth is found in the southwestern Indian Ocean near the Comoros, as well as in Sodwana Bay, off the coast of Kenya and Mozambique, Madagascar. The Indonesian coelacanth was caught off the coast of Indonesia.

Coelacanth-like (for example, coelacanth) fish are characterized by benthic nutrition; anchovies, deep-sea cardinals, cephalopods and cuttlefish, large-headed sharks, snappers make up a significant part of the daily menu of these fish. Due to the peculiarities of the structure of the skull, coelacanths suck food along with water, sharply opening their mouth.

Indonesian coelacanth (Latimeria menadoensis), drawing picture
Indonesian coelacanth (Latimeria menadoensis), drawing picture

Indonesian coelacanth (Latimeria menadoensis)

Today, coelacanths are considered viviparous with a gestation period of more than a year, whereas earlier they were considered oviparous (the first individual whose reproduction was studied had large eggs in the body). Later, the coelacanth was opened with embryos in the oviducts.

The surviving representatives of coelacanths (coelacanths) are considered exclusively as a unique object of scientific research, although they were rarely eaten before.

Systematics of the order Celacanthus, Latimeria:

  • Order / Order: Coelacanthiformes Berg, 1937 = Coelacanthus, coelacanths

    • Suborder / Suborder: Coelacanthoidei =

      Family: Coelacanthidae Agassiz, 1843 =

    • Suborder / Suborder: Hadronectoroidei =
    • Suborder / Suborder: Latimerioidei Schultze, 1993 =

      • Family: Latimeriidae Berg, 1940 = Latimeriids

        • Genus: Holophagus =
        • Genus: Latimeria Smith, 1939 = Latimeria, or coelacanth

          • Species: Latimeria chalumnae James Leonard Brierley Smith, 1939 = Comorian coelacanth, or coelacanth
          • Species: Latimeria menadoensis Pouyaud, Wirjoatmodjo, Rachmatika, Tjakrawidjaja, Hadiaty and Hadie, 1999 = Indonesian Celacanth
        • Genus: Libys =
        • Genus: Macropoma =
        • Genus: Megalocoelacanthus =
        • Genus: Swenzia =
        • Genus: Ticinepomis =
      • Family: Mawsoniidae =

Literature:

1. Naumov NP, Kartashov NN Zoology of vertebrates. - Part 1. - Lower chordates, jawless, fish, amphibians: A textbook for a biologist, special. un-tov. - M.: Higher. school, 1979. - 333 p., ill.

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