Gill trap
The gill trap of the fish is an organ system made up of toothed appendages on the gullet side of the gill arches , which serves to separate food and respiratory water. These projections are referred to as Branchiospinen (Reusendornen, Kiemenreusendornen), the spines arranged in series on the gill arches are called Branchioctenia (combs).
In vertebrates and their ancestors, whose pre- Silurian forms are very poorly known, there is a pharynx (gill intestine), i. H. the foregut next to the oral cavity has crack-shaped openings (also through the body skin) to the outside, which makes it possible to filter off plankton as food and swallow it straight away (see also lancet fish , tunicates ). As soon as the ancestors of the vertebrates were a few millimeters tall and skin breathing was no longer sufficient for them, the gill intestine offered itself as an additional respiratory organ. However, this requires an appropriately functioning blood vessel system - the heart was created in a position just “in front of” this pharynx.
All water-breathing jaws have toothed appendages on the inside of the gill arches to separate food and water from each other. In the case of fish that devour large, but dead prey, the trap can be reduced to traces (this also applies to predatory fish such as the barracudas , which kill their prey before devouring), otherwise it is always necessary, for example for living prey on it to prevent escaping through the crevices.
The densest Reuse naturally have plankton (u. A. Basking , whale shark , megamouth , Manta , paddlefish , herring , anchovies , whitefish , Cyclothone microdon , Indian Mackerel ). A big mouth has in such fish then out that if necessary (for "jam filters" eng . Ram feeding can move (z. B. Indian Mackerel)). The trap consists of stiff, connective tissue , cartilaginous or bony, often mobile appendages of the branchial arches of various sizes, shapes and arrangements (also branched) - one row each at the front and rear edge of the crevice . Through their entanglement, the fish trap rays also stabilize the gill intestine. They are always positioned in such a way that the crevices do not clog ( cross-flow filtration ): the food particles slide off and are "washed" towards the esophagus , where they are grabbed by the pharyngeal teeth and often crushed (especially in carp-like animals ). The gap between the 4th and 5th arch is often already closed (connective tissue). There are only very rarely spins on the hyoid arch , but the anterior ones on the first gill arch are often elongated.
In the lower real bony fish (Teleostei) with microphagia (eating of microorganisms), the gill trap is functionally usually supplemented by the paired epibranchial organ (at the upper rear end of the pharynx): it produces mucus that adheres to the microorganisms in order to be more easily swallowed. Branchiospinen usually reach into this organ, so that the food particles z. T. can be grated, probably to "judge the taste". See: Heterotis niloticus , real herrings , anchovies , Argentinidae , Alepocephalus rostratus , Coregonus , Gonorynchus and Citharinidae . Higher Teleostei with plankton or detritus nutrition have analogous mucus-producing skin organs in the gill intestine, e.g. B. the Mugilidae .
Individual evidence
- ^ Blaise Zaugg, Jean-Carlo Pedroli (Aquarius Office, Neuchâtel, Erich Ritter, Zoological Museum, Zurich): Freshwater fish - simply determined. ( Online )
literature
- Wilfried Westheide, Reinhard Rieger (Hrsg.): Special zoology. 2nd Edition. Part 2: vertebrates or skulls. Spectrum Akademischer Verlag, Heidelberg 2010, ISBN 978-3-8274-2220-0 .
- Gunnar Bertmar: Epibranchial organ en adapting till planktonupptagning hos benfiskar. In: Zoologisk revy. 35, 1973, pp. 5-10.