Fish
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Spotted fish ( Lepisosteus oculatus ) in an aquarium of the Aquazoo in Düsseldorf. |
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| Cuvier , 1825 |
The bony pike (Lepisosteidae ( Gr .: lepis = scale, osteon = bone)), also called caiman fish or alligator fish , are a family of bony fish , with two genera and seven species in North and Central America from southern Québec (Canada) to Costa Rica , Panama and Cuba occur. They are large to very large predatory fish, which in their way of life resemble the pike , which is not related to them . The American name even corresponds to the Germanic word "Ger" (spear).
distribution
False pike live exclusively in North and Central America. They occur in the rivers east of the Appalachian Mountains , in Florida , in the catchment area of the Mississippi and in the Rio Grande , in the Great Lakes with the exception of Lake Superior and in the Saint Lawrence River , as well as in Cuba, the Isla de la Juventud and Central America . Adult specimens are often in the brackish water of the estuaries, the largest species, the alligator pike and the Cuban fish , go, very rarely, into the sea.
features
body
Bake are, depending on the species, 88 centimeters to 3.05 meters long. Their body is cylindrical, elongated and round in cross-section. Similar to the pike , the body of the pike is surrounded by a closed shell consisting of strong, non-overlapping and inclined rows of ganoid scales . The scales are rhombic, usually articulated and without a dentin layer .
All fins only have soft rays. The pectoral and pelvic fins sit deep on the body, the dorsal and anal fins are symmetrically opposite each other and are shifted far back, in order to serve together with the tail fin as a driving organ when catching prey like a shock robber. The caudal fin is almost symmetrical on the outside, but clearly asymmetrical and heterocerky on the inside . The asymmetry of the caudal fin can also be recognized by a sudden change in the orientation of the scales on the tail fin stalk, the so-called chondrosteer hinge. The sideline is accompanied by 50 to 65 scales. All the front fin edges are reinforced by special scales called hem follicles.
The vertebrae are cylindrical and opisthocoel, that is, the front is convex and the back is concave. This form of vertebra was created by ossification and fusion of a lenticular chordal part with amphicoelic vertebrae (vertebrae with two concave sides.) Pike are the only fish whose vertebrae articulate with each other (and with the occiput). The old name Ginglymodi , often used in cladistics for the taxon, refers to these articulated vertebral bodies. The abdominal ribs of the juvenile fish encompass the body cavity, in adults they are shifted towards the back and the free ends bend towards the belly just under the skin. The tail skeleton does not yet show the regularity of the real bony fish (Teleostei), but is of high intra-species variability.
head
The jaws are long and can make up to 80% of the length of the head. In the smaller species and juvenile fish, the jaws are tweezer-like and the mouth with numerous pointed, needle-like fangs is reminiscent of a gavial mouth . Very large species also have a crocodile-like broad snout when old. The two genera differ, among other things, in the number of rows of large fangs in the upper jaw: Atractosteus has two rows on each side of the jaw, Lepisosteus only one. The rows of fangs are lined on the outside by another row of very dense, small teeth. There is always only one row of fangs in the lower jaw. The fangs have a corrugated base and show a fold structure in cross-section, which is created by folding in the dentin . In the upper jaw, the teeth are supported by a row of bone plates that is formed by numerous individual bones known as infraorbitalia or lacrimalia, which are difficult to homologate (to bring them into conformity with the jawbones of other fish). The maxillary is small, arched, in most cases edentulous, and is immovable close to the temporomandibular joint. Supramaxillaria are absent. The roof of the snout is mainly formed by extensions of the premaxillaries . The lower jaw is mainly formed by an elongated dentine and a coronoid process . The temporomandibular joint, in which articular and retro- articular elements are involved, is in front of the eyes, the nostrils at the end of the muzzle. The tongue has a skeleton of a connective tissue plate and a pair of rows of bone plates that articulate with one another. The cheek region is covered with fragmented bone plates. The gill cover has no interoperculum. There are two or more supratemporal bones on each side of the head. The ploughshare (vomer) is paired. The gill arches have simple tooth plates and toothed gill spines , which are flattened in the Atractosteus species and small and pear-shaped in the Lepisosteus species. On the inside of the gill cover there is a gill cover gill. The pike are the only new fins in which the adults still have this gill. On the other hand, the larvae still have a pair of injection holes , which however soon close. The underside of the gill region is protected by three Branchiostegal rays . Gular plates, as in the case of the pike or the bald pike , are missing because of the narrowness of the "Kehl" region.
Internal organs
Several rows of valves are formed at the muscular transition from the heart to the aorta. The rear intestine has an elongated, indistinct spiral fold . The paired ovaries of the females lie one behind the other in the body cavity, the right one in front of the pelvic fin , the left one behind it. The swim bladder is very large, richly chambered, well supplied with blood vessels and is also used for air breathing . It is connected to paired pulmonary arteries that extend from the posterior gill arch.
Way of life
Bake fish prefer to stay in shallow water with dense vegetation during the summer, where they often come to the surface in order to take in air, often with their pines stretched out high. The swim bladder, which is well supplied with blood vessels, enables auxiliary breathing to support the gills. All bake are stalking hunters who rarely move quickly. Bake fish living in freshwater feed almost exclusively on small fish, but the very large species can also prey on water fowl . In brackish water, shrimp are added to the food spectrum. Similar to the pike native to Europe, they do not actively hunt their prey, but lurk hidden, only to strike suddenly. After being snapped shut, the prey is rotated so that it can be swallowed. Large fish destroy fishing nets trying to get their contents. The pike that live in the temperate climate zone overwinter close to the ground.
Reproduction
The reproduction takes place exclusively in fresh waters. The pike, which live in the temperate climate zone about the same height as New York City , spawn from mid-May to mid-June in shallow, vegetation-rich water with low currents. A large female spawns with several smaller males. The eggs are green, poisonous, very sticky and stick to aquatic plants or the ground. The hatching yolk sac larvae hang on the vegetation with the help of their forehead adhesive organ until the yolk sac is consumed. The initially short-snouted larvae have a filament-like extension of the caudal fin. (This device is found more often in fish, for example in shovel sturgeons - it serves to protect against predators that approach from behind.) They are fast-growing and soon show the typical long jaws.
External system
The pike are commonly considered to be at the base of the more modern ray-fins ( Neopterygii ). There they are usually placed together with closer fossil relatives in a separate superordinate group, the bonehike-like ( Lepisosteiformes ). However, there are two competing hypotheses about the exact position of the pike-like among the basal neopterygians. One puts it together with the bald pike ( Amia calva ) and its extinct relatives in the group of bone organoids (Holostei). The other says that the bald pike is more closely related to the real bony fish (Teleostei) than to the bony pike ( Halecostomi hypothesis ). The bonehike-like thus formed together with extinct relatives the sister group of the Halecostomi, which is called Ginglymodi . As an alternative to these two hypotheses, the pike along with the extinct basal Neopterygian families Semionotidae and Dapedidae have been grouped under the name Semionotiformes .
According to a more recent version of the Ginglymodi hypothesis, the Ginglymodi consist of two subclades: Lepisosteiformes and Semionotiformes. The pike belong to the Lepisosteiformes and the Semionotiformes are now defined as all representatives that are more closely related to Semionotus than to Lepisosteus .
The following cladogram shows the systematic position of the pike according to the Halecostomi hypothesis (fossil taxa are excluded):
| Actinopteri |
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Position of the pike according to the Holosteer hypothesis (without fossil taxa). This variant is mainly supported by molecular genetic data:
| Actinopteri |
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Internal system
The family includes seven recent species in two genera:
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Cladogram of recent pike
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- Genus Atractosteus
- Alligator pike ( Atractosteus spatula ) (305 cm)
- Cuban fish ( Atractosteus tristoechus ) (200 cm)
- Tropical fish ( Atractosteus tropicus ) (125 cm)
- Genus Lepisosteus
- Spotted Bake ( Lepisosteus oculatus ) (112 cm)
- Common Bake ( Lepisosteus osseus ) (200 cm)
- Short- snouted fish ( Lepisosteus platostomus ) (88 cm)
- Florida fish ( Lepisosteus platyrhincus ) (132 cm)
Fossil record
Bake fish are a very old group of fish and can be found in fossils in Africa as early as the beginning of the Lower Cretaceous ( Berriasian ) 145.5 million years ago. The oldest fossils in today's range are 125 million years old. Extinct genera of the bonefish are Masillosteus and Cuneatus . Masillosteus lived in the Eocene and was very short-nosed. The genus had only a few pointed teeth, but the coronoid and upper jaw were covered with large, flat-crowned teeth that were suitable for cracking snails or other hard-shelled organisms. The recent genus Lepisosteus is mainly known from the Cretaceous and the Eocene of North and South America, Europe and India, Atractosteus from North and South America, Africa and Europe, including Atractosteus strausi also from the Eocene of the Messel pit in southern Hesse.
use
Bake meat is not considered tasty, in some cases even as inedible. The big fish are mainly caught for reasons of sporting challenge. Jewelry is made from the ganoid scales . They can often be seen in public show aquariums and can live there for over 50 years. One specimen in Zurich Zoo lived to be 71 years old. They have not yet been bred in human care.
swell
literature
- Peter Bartsch: Ginglymodi (Lepisosteiformes), pike, caiman fish. Page 236–238 in Wilfried Westheide & Reinhard Rieger : Special Zoology Part 2: Vertebrae and Skull Animals , 1st edition, Spectrum Academic Publishing Heidelberg • Berlin, 2004, ISBN 3-8274-0307-3 .
- The living marine resources of the Western Central Atlantic. Volume 2: Bony fishes part 1 (Acipenseridae to Grammatidae) . In: Kent E. Carpenter (Ed.): FAO Species Identification Guide for Fishery Purposes and American Society of Ichthyologists and Herpetologists Special Publication . tape 5 . FAO, Rome 2002, p. 672 ( full text [PDF]).
- Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish . Gustav Fischer Verlag, Jena 1991, ISBN 3-334-00339-6 .
- Guillaume Lecointre, Hervé Le Guyader: Biosystematics: All organisms at a glance. Springer, Berlin, 2005, ISBN 3540240373 .
- Joseph S. Nelson : Fishes of the World. John Wiley & Sons, 2006, ISBN 0-471-25031-7 .
- Günther Sterba : The world's freshwater fish. 2nd Edition. Urania, Leipzig / Jena / Berlin 1990, ISBN 3-332-00109-4 .
Individual evidence
- ↑ a b Fiedler (1991), page 259.
- ↑ a b c d Nelson (2006), page 97 f.
- ↑ a b Lecointre (2001), page 452 ff.
- ↑ a b c d e f Bartsch (2004)
- ↑ a b c Order Summary for Lepisosteiformes on Fishbase.org (English)
- ↑ a b Sterba (1990), page 27
- ↑ a b Lance Grande: An Empirical Synthetic Pattern Study of Gars (Lepisosteiformes) and Closely Related Species, Based Mostly on Skeletal Anatomy. The Resurrection of Holostei . In: The American Society of Ichthyologists and Herpetologists Special Publication . 6 (Supplementum for the 2010 Copeia year), 2010, p. 1-871 .
- ^ A b c Adriana López-Arbarello: Phylogenetic Interrelationships of Ginglymodian Fishes (Actinopterygii: Neopterygii) . In: PLoS ONE . tape 7 , no. 7 , 2012, p. e39370 , doi : 10.1371 / journal.pone.0039370 .
- ^ Lionel Cavin, Varavudh Suteethorn: A new semionotiform (Actinopterygii, Neopterygii) from Upper Jurassic-Lower Cretaceous deposits of north-east Thailand, with comments on the relationships of semionotiforms . In: Palaeontology . tape 49 , no. 49 , 2006, pp. 339-352 , doi : 10.1111 / j.1475-4983.2006.00539.x .
- ↑ Jeremy J. Wright, Solomon R. David, Thomas J. Near: Gene trees, species trees, and morphology converge on a similar phylogeny of living gars (Actinopterygii: Holostei: Lepisosteidae), an ancient clade of ray-finned fishes. Molecular Phylogenetics and Evolution 63 (2012) 848-856 PDF
- ^ The Paleobiology Database: Lepisosteiformes
- ^ Karl Albert Frickhinger: Fossil Atlas of Fishes. Mergus-Verlag, Melle, 1999, ISBN 3-88244-018-X
- ↑ Wolf-Eberhard Engelmann: zoo animal husbandry - animals in human care - fish. Pages 242–243, Verlag Harri Deutsch, 1st edition, 2005, ISBN 3-8171-1352-8
Web links
- Family Lepisosteidae - Gars on Fishbase.org (English)
- Order Summary for Lepisosteiformes on Fishbase.org (English)
- Palæos: Lepisosteiformes