Flatfish

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Flatfish
Turbot (Scophthalmus maximus)

Turbot ( Scophthalmus maximus )

Systematics
Acanthomorphata
Spinefish (Acanthopterygii)
Perch relatives (Percomorphaceae)
Carangaria
Order : Carangiformes
Partial order : Flatfish
Scientific name
Pleuronectoideo
Bleeker , 1859

The flatfish (Pleuronectoideo) are a group of the real bony fish (Teleostei), which stand out due to their special physique, which is adapted to a benthic way of life on the water floor. Adult flatfish are strongly flattened on the sides and, since both eyes are on the same side of the body, they are built asymmetrically. Flatfish include numerous edible fish such as plaice , turbot , halibut , flounder and sole .

distribution

Flatfish are found in all seas, both in the tropics and in temperate zones. Many species are also found in cold waters, even in the polar seas. Most species live in the Pacific . The habitat is mainly sand, gravel and stone on the continental slopes in shallow water, but some species are also found in the deep sea. Some species of flatfish also live in fresh water. Freshwater species can be found at the American soles (Achiridae), the dog tongues (Cynoglossidae), the bill Butten (Paralichthyidae), the plaice (Pleuronectidae), the South Pacific flounder (Rhombosoleidae), the turbot (Scophthalmidae) and the sole (Soleidae). Some freshwater species are primarily found in freshwater, but they also have the ability to live in brackish water and in the ocean. Another twenty primarily marine species also visit fresh waters.

features

The adult flatfish's body is disc-shaped or diamond-shaped and heavily flattened on the sides. The top is pigmented and the color can be matched to the background. It is covered with small comb scales , more rarely with round scales or tubercle-shaped scales. The underside (blind side) is mostly whitish and in most cases covered with weak round scales. Flatfish reach lengths from a few centimeters to over three meters. The number of their vertebrae is from 27 to 70.

Lamb's tongue larva ( Arnoglossus laterna )
Young turbot that has not yet fully metamorphosed.
Sole hidden in the sand.
Microchirus ocellatus

Both eyes are on the colored top. As larvae, flatfish still have a bilaterally symmetrical body shape and swim upright in open water. In the course of growth, usually between 10 and 25 mm in length, one eye wanders in front of the dorsal fin or through its base to the later upper side of the body and then comes to a standstill in a bone cavity between the frontalia and prefrontalia. The skull bones as well as the outer nostrils shift in the same direction. Muscles and nerves, the protractile (protruding) mouth, the teeth and the paired fins are also involved in this metamorphosis . The maxillary margin is only formed by the premaxillary , base phenoid and supramaxillary are not present.

The brain remains in the original plane of symmetry. The top begins to take on a darker color. The eyes of the butterflies almost always move to the left side, in the case of plaice and sole usually to the right. However, there are also ways in which both sides can become the top. In the meantime, the body flattens out, and in most species the swim bladder recedes. The eyes can protrude high above the body surface and allow the fish buried in the ground to search the area for enemies or food. The gill chambers are connected to one another so that the respiratory water that has flowed over the gills on the blind side can also be expelled through the gill opening on the upper side. The number of Branchiostegal rays is usually six or seven, rarely eight.

The dorsal and anal fins are fringed and elongated and, apart from the hard ray flounder , are only supported by segmented soft rays. They can also be connected to the tail fin to form a continuous fin edge, e.g. B. in the dog tongues . The dorsal fin begins, except in Psettodes , above the neurocranium . The pelvic fins are throaty and in many cases, like the pectoral fins , of different sizes. The number of fin rays in the pelvic fins is usually less than seven. The shoulder girdle usually remains symmetrical, the pelvic girdle is reduced. The end of the caudal fin is usually rounded, less often pointed. Adult flatfish, with the exception of the sole genus Monochirus , do not have a swim bladder. They swim blind side down and move with undulating movements of the whole body.

Way of life

Flatfish live on the bottom of the water and feed carnivorously , mostly on invertebrates living on the ground. Large species like halibut and psettodes are predatory fish that prey on other fish. Species with a symmetrical mouth opening and regular teeth tend to hunt in the open water, while species with an asymmetrical mouth opening and stronger teeth on the underside tend to eat from the seabed.

Flatfish are oviparous and sexually mature between one and 15 years of age. Eggs and larvae are planktonic . Many species undertake long walks in search of food or to get to the spawning grounds.

External system

Flatfish are real bony fish (Teleostei) and belong to the perch relatives (Percomorphaceae) within the barbedfish (Acanthopterygii ). As a taxonomic group, they were introduced in 1859 by the Dutch ichthyologist Pieter Bleeker . Traditionally, they were given the scientific name Pleuronectiformes in the order of rank. Molecular biological studies have shown that they are related to the mackerel relatives (Carangoidei), the giant perches (Latidae), the swordfish-like (Xiphioidea), the barracudas (Sphyraenidae), the archer fish (Toxotidae) and other taxa that used to be classified as perch-like . In a revision of this group published in May 2020 , all relatives of the jack-mackerel relatives were united in the order Carangiformes . The revision was taken over by the monthly updated systematic fish database "Eschmeyer's Catalog of Fishes" at the beginning of June 2020. The flatfish now only have the rank of a partial order with the scientific designation Pleuronectoideo. Together with its sister group , the Fadenflossern (Polynemidae) to form the subordination Polynemoidei within the Carangiformes.

Internal system

plaice

There are over 675  species , in 134  genera , 16  families , three superfamilies and two subordinates. The Psettodidae are the most original family and the sister group of all other flatfish known as Pleuronectoidei.

The suspected relationships according to Campbell et al. shows the following cladogram :

  Pleuronectiformes  
  Psettodoidei  

 Hard ray flounder (Psettodidae)


  Pleuronectoidei  
  Citharoidea  

 Citharidae (Citharidae)


   
  Pleuronectoidea  

 Turbot (Scophthalmidae)


   


 Plaice (Pleuronectidae)


   

 Sham butt (Paralichthyidae)



   

 Butte (Bothidae)


   

 Cyclopsettidae





  Soleoidea  


 American sole (Achiridae)


   

 Paralichthodidae


   

 Oncopteridae


   

 South Pacific flounder (Rhombosoleidae)


   

 Southern flounder (Achiropsettidae)




Template: Klade / Maintenance / 3

   

 Comb flounder (Samaridae)


   

 Poecilopsettidae


   

 Dog tongues (Cynoglossidae)


   

 Sole (Soleidae)









Template: Klade / Maintenance / Style

Tribal history

Eobothus minimus

Flatfish are known at the latest from the geological period of the Eocene , which began about 55 million years ago. The fossil genera Amphistium and Heteronectes from Eocene Europe are considered to be mosaic forms in which the eyes of the adult animals were still permanently on both sides of the body, but one already very high up near the middle of the back. Another genus from the Eocene is Eobothus , which was found among other things in the northern Italian Monte Bolca formation and which is already assigned to the Butte family. From the Miocene comes Scophthalmus heckeli from the family of turbot and in sub-Kirchberg sole found Solea kirchbergeana . The clods are fossilized with the genus Liopsetta from the Sakhalin Pliocene .

literature

  • Kurt Fiedler: Fish (= textbook of special zoology. Vol. 2: Vertebrates. Part. 2). Gustav Fischer, Jena 1991, ISBN 3-334-00338-8 .
  • Arno Hermann Müller : Textbook of paleozoology. Volume 3: Vertebrates. Part 1: fish in the broader sense and amphibians. 2nd, revised and expanded edition. Gustav Fischer, Jena et al. 1985, ISBN 3-334-00222-5 .
  • Joseph S. Nelson : Fishes of the World. 4th edition. John Wiley & Sons, Hoboken NJ et al. 2006, ISBN 0-471-25031-7 .

Individual evidence

  1. ↑ a b c d e Matthew A. Campbell, Bruno Chanet, Jhen-Nien Chen, Mao-Ying Lee, Wei-Jen Chen (2019): Origins and relationships of the Pleuronectoidei: Molecular and morphological analysis of living and fossil taxa. Zoologica Scripta, 48: 640-656. doi: 10.1111 / zsc.12372
  2. ↑ Ricardo Betancur-R, Edward O. Wiley, Gloria Arratia, Arturo Acero, Nicolas Bailly, Masaki Miya, Guillaume Lecointre and Guillermo Ortí: Phylogenetic classification of bony fishes . BMC Evolutionary Biology, BMC series - July 2017, DOI: 10.1186 / s12862-017-0958-3
  3. ^ A b Matthew G. Girard, Matthew P. Davis, W. Leo Smith: The Phylogeny of Carangiform Fishes: Morphological and Genomic Investigations of a New Fish Clade. Copeia, 108 (2): 265-298 (2020). doi: 10.1643 / CI-19-320
  4. ↑ Eschmeyer's Catalog of Fishes: Species by Family / Subfamily
  5. ^ Matt Friedmann: The evolutionary origin of flatfish asymmetry. In: Nature . Vol. 454, No. 7201, 2008, pp. 209-212, doi : 10.1038 / nature07108 .
  6. ^ Karl Albert Frickhinger: Fossil Atlas of Fishes. Mergus - Verlag für Natur- und Heimtierkunde Baensch, Melle 1991, ISBN 3-88244-018-X .

Web links

Commons : Flatfish  - Collection of images, videos and audio files
Wiktionary: Flatfish  - explanations of meanings, origins of words, synonyms, translations