Spiral valve

The spiral intestine, and spiral intestine, is an organ niedererer fish and comes with sharks, rays, short nose chimeras and some original bony fish before (non- Teleostei ). The necessary for digestion enlargement of the inner surface of the intestine is in these vertebrates not achieved by an intestinal lengthening and looping, as in genuine bony fish and terrestrial vertebrates, but by such a narrow spiral staircase spiral fold in short, cigar-shaped and straight intestine. Maximum may be present nearly 60 whorls. But there are also spindle -less and roulades like rolled spiral folds.

The name is (since Rathke 1824) firmly naturalized - but he is not accurate, a real (double) intestinal spiral like tadpoles are rare, eg the bitterling. In Campostoma anomalum ( Cyprinidae ) of the midgut approximately eight times ( schraubig ) is " wrapped" around the swimming bladder. With the " real" spiral intestine of these cases have nothing to do.

Evolution History of the spiral intestine is both a result of enlargement of the digestive and resorbing surface of the mucous membrane, is used due to its high internal stability (in the sense of Wolfgang Friedrich Gutmann ) but also the mechanical support of the notochord. This feature could be omitted again because the spine, she took over more and more at more advanced taxa.

The spiral intestine is undoubtedly an old ( plesiomorphes ) feature of gnathostomes, perhaps even of vertebrates. Even from arthrodires are known schraubige coprolites; Lampreys have at least a " spiral " (screw ) fold, which perhaps represents a regression from a spiral intestine. ( Only the hagfish (Primary? ) Nothing of the sort, but merely irregular, coarse mucosal folds. ) The sharks of the spiral intestine begins just behind the stomach and makes the entire midgut from. When we find disturbing, however, already a midgut loop, the " intermediate intestine"; the spiral intestine is limited to its decline. Amia has four whorls, Lepisosteus virtually no more; see also Chirocentrus.

Swell

• Keyword spiral intestine in Dictionary of Biology. ISBN 3-451-19648-4
• Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: fish. Gustav Fischer Verlag, Jena, 1991, ISBN 3-334-00339-6

• Anatomy of the fish
• Digestive Disorders