Pharyngealia

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Pharyngealia of a moray eel

Among the pharyngeal jaw refers to those parts of the gill arch skeleton (s. Also pharyngeal arch ) of the fish, especially the Actinopterygii , which were in the course of evolution, more and more specialized in the transport of food through the pharynx (gill gut, "throat") and often their Processing for better digestion (as a "chewing device") to serve.

Phylogenetic evolution

Skull of anarhichas (sea wolf). At the upper edge of the mouth one sees the paired premaxillary (intermaxillary bone) with the “fangs” (for tearing off firmly spun mussels) and the almost toothless side branch; behind it in the roof of the mouth medially ("located towards the middle") the pinch teeth on the unpaired vomer and laterally from it ("located to the side") those on the palatina. The fangs and crush teeth of the (paired) dentals (in the lower jaw) act as antagonists to the teeth on these five bones. Further back (inside) the upper and lower pharyngealia with smaller teeth that transport the mollusc through the throat.

One can clearly distinguish two steps of development. First, the rearmost arch ("fifth gill arch") develops a corresponding dentition ventrally (from Devonian ); From the Jurassic onwards, however, a complex muscular apparatus also developed dorsally on the gill arches II to IV (with the dentate pharyngobranchials II-IV; the pharynx I serves as a connecting rod for the entire apparatus), which enables prey to be reached much more quickly and efficiently devour. A long (paired) muscle from the spine is particularly important: the retractor pharyngealium dorsalis (C. Holstvoogd 1965), which arises from the esophagus muscles.

So that the gill arches execute coordinated movements (like a pantograph ) to loop, it is necessary that the dorsal ("back") bone elements (epibranchialia) develop mutually directed processes (the uncinate processes). This is the case with the Acanthopterygii , in a similar way ( autapomorphic ) but also with the mud fish , with moray eels , carp, etc. With the moray eels, the pharyngealia can be moved so far forward that they take over prey packed with the jaws or from it Can tear pieces or wound an attacked enemy.

The ventral pharyngealia mentioned initially act against each other when snapping and “chewing” or, in carp fish , also against a chewing plate at the base of the skull. If, however, dorsal pharyngealia are also present, they work together with the ventral ones, which can now grow together ( wrasse ) or fuse ( puffer fish ) to strengthen their performance . All pharyngeal teeth ( sturgeons , gonorynchiformes , Gyrinocheilidae ) are seldom missing , but even more rarely all pharyngealia ( pike ).

literature

  • Wilfried Westheide , Reinhard Rieger: Special Zoology. Part 2: Vertebrae and Skull Animals. 1st edition. Spectrum Academic Publishing House, Heidelberg / Berlin 2004, ISBN 3-8274-0307-3 .
  • P. Vandewalle, E. Parmentier, M. Chardon: The branchial basket in Teleost feeding. In: Cybium. 24, 2000, pp. 319-342. (Abstract)