Ray fins

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Ray fins
Actinopterygii-0001.jpg

Ray fins ( Actinopterygii )

Systematics
without rank: Bilateria
Over trunk : Neumünder (Deuterostomia)
Trunk : Chordates (chordata)
Sub-stem : Vertebrates (vertebrata)
Superclass : Jaw mouths (Gnathostomata)
Class : Ray fins
Scientific name
Actinopterygii
Cope , 1871

The ray fins (Actinopterygii) are a class of bony fish (Osteichthyes).

With the exception of the meat fin (Sarcopterygii), all bony fish belong to this taxon , which is almost half of all vertebrate species .

The ray fins are distributed worldwide today and colonize all aquatic habitats from the deep sea (up to about −8,400 meters) to the high mountains (up to about 4,500 meters) and from thermal springs (+43  ° C ) to the polar seas (−1.8 ° C) ). They are very variable in morphological , ecological and behavioral aspects.

Origin of name

The scientific name "Actinopterygii" is made up of the ancient Greek words ἀκτίς ( aktís , 'ray') and πτερύγιον (pterýgion, 'wing' or 'fin'), so it corresponds to the German trivial name "Strahlflosser". It refers to the typical anatomy of the fins (see below).

Morphological features

One of the most characteristic features of the ray fins, which gives the taxon its name, is the formation of paired fins (pectoral and pelvic fins) in the form of so-called ray fins (Actinopterygia, Sg. Actinopterygium). The sister group of the ray fins, the flesh fins (Sarcopterygii), however, have so-called flesh fins (Sarcopterygia, Sg. Sarcopterygium). The majority of these fins consists of the bony fin rays (Radii, Sg. Radius) and the webbing (Patagium), which is spanned by the radii. The relatively long radii sit on a comparatively short fin base skeleton, with proximal (close to the trunk) basals being distinguished from distal (distal), rod-shaped radials. However, the basalia are absent from almost all of the ray-fin taxa living today. In all bony fish, the muscles for the fin movement are only attached to the base of the fin. Correspondingly, the entire fin base, i.e. H. Fin base skeleton and muscles, rather inconspicuous in ray fins. In the meat fins, the fin base, and in some cases also the unpaired fins, is much longer and stronger than the fin rays, so that a relatively large part of the fin in living animals is "fleshy".

The crowns of the actinopterygians are characterized in addition to the coating of normal enamel ( Ganoin ) by an additional small cap or "wart" from Acrodin, a very hard, transparent melt-like substance on the top of the crown (apex) of.

The front of the two dorsal fins in the basic plan of the bony fish is missing: This primarily single dorsal fin of the ray fins can be divided into several fins secondarily.

The scales are articulated to one another by a hook system. They are originally heavily mineralized, i. H. covered with a layer of ganoin ( ganoid scale ). This condition is widespread in fossil ray fins of the Paleozoic and Mesozoic Era , but is only found today in sturgeon (Acipenseridae) and bake (Lepisosteidae). By far the most common type of scale in the radiation fins living today is the elasmoid scale . In this case, the ganoin is reduced to microscopic remains.

First appearance in the fossil record

The Lophosteiformes and Naxilepis , fragmentary finds from the late Silurian (about 420  mya ) from Europe and Siberia and China, were once considered to be the oldest fossil remains of ray fins. In the meantime, however, these representatives are classified as basal bony fish. Meemannia , originally classified as a primitive meat finisher, shows a ray-fin-like skull and is around 415 million years old ( Lower Devonian ). The oldest skeletal finds that can be safely assigned to ray fins come from the Central Devonian (about 380 mya) of Europe and Canada ( Cheirolepis ). Other European skeleton finds from this period are Stegotrachelus , Moythomasia and Orvikuina .

Systematics

The radiation fins include over 30,000 species, of which 15,150 are freshwater fish , 14,740 are found in the sea and 720 species can live in both biotopes and in brackish water .

In the following, the system is presented according to the standard work Fishes of the World († = extinct):

Ray fins (Actinopterygii)

literature

  • Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish , Gustav Fischer Verlag, Jena, 1991, ISBN 3-334-00339-6
  • Gerhard Mickoleit: Phylogenetic Systematics of Vertebrates , Verlag Dr. Friedrich Pfeil, Munich, 2004, 671 pages, ISBN 3-89937-044-9
  • Joseph S. Nelson, Terry C. Grande, Mark VH Wilson: Fishes of the World. Wiley, Hoboken, New Jersey, 2016, ISBN 978-1118342336
  • Wilfried Westheide & Reinhard Rieger: Special Zoology Part 2: Vertebrae and Skull Animals , 2nd edition, Spectrum Akademischer Verlag Heidelberg • Berlin, 2010, ISBN 978-3-8274-2039-8

Individual evidence

  1. ↑ a b c d Guillaume Lecointre, Hervé Le Guyader: Biosystematics . Springer, Berlin / Heidelberg 2006. p. 437 f.
  2. ↑ Paul H. Yanceya, Mackenzie E. Gerringera, Jeffrey C. Drazen, Ashley A. Rowden, Alan Jamieson: Marine fish may be biochemically constrained from inhabiting the deepest ocean depths. In: PNAS (Early Edition), doi : 10.1073 / pnas.1322003111 and the literature cited therein
  3. ↑ Milton Hildebrand, George E. Goslow: Comparative and functional anatomy of the vertebrates. Springer, Heidelberg / Berlin 2004. p. 183 u. 673
  4. ^ Hector Botella, Henning Blom, Markus Dorka, Per Erik Ahlberg, Philippe Janvier: Jaws and teeth of the earliest bony fishes . In: Nature . tape 448 , 2007, p. 583-586 , doi : 10.1038 / nature05989 .
  5. ↑ Zhu Min, Zhao Wenjin, Jia Liantao, Lu Jing, Qiao Tuo, Qu Qingming: The oldest articulated osteichthyan reveals mosaic gnathostome characters . In: Nature . tape 458 , 2009, p. 469-474 , doi : 10.1038 / nature07855 .
  6. ↑ Jing Lu, Sam Giles, Matt Friedman, Jan L. den Blaauwen and Min Zhucor. 2016. The Oldest Actinopterygian Highlights the Cryptic Early History of the Hyperdiverse Ray-Finned Fishes. Current Biology. DOI: 10.1016 / j.cub.2016.04.045
  7. ↑ Greta Carrete Vega, John J. Wiens: Why there are so few fish in the sea? In: Proceedings of the Royal Society B: Biological Sciences. 279, 2012, pp. 2323-2329, doi : 10.1098 / rspb.2012.0075
  8. ^ Joseph S. Nelson, Terry C. Grande, Mark VH Wilson: Fishes of the World. Wiley, Hoboken, New Jersey, 2016, ISBN 978-1118342336

Web links

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