Paddlefish
| Paddlefish | ||||||||||||
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Paddlefish ( Polyodon spathula ) |
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| Systematics | ||||||||||||
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| Polyodontidae | ||||||||||||
| Bonaparte , 1838 |
The spoonbill sturgeon (Polyodontidae ( Gr .: poly = many, odous = tooth)) are a family of sturgeon-like (Acipenseriformes) that contain only two genera with one species each . The species are the paddle sturgeon ( Polyodon spathula ) from the Mississippi River basin (USA) and the sword sturgeon ( Psephurus gladius ) from the Yangtze River (China). The existence of the paddle sturgeon is severely threatened by fishing, water pollution and the construction of dams; the sword sturgeon is now considered extinct.
features
Paddlefish grow to be 2.2 to 3 meters long. Reports of 7-meter-long sword sturgeon are not considered credible. The mighty, extended forehead, which makes up a considerable part of the total length of the animals (up to a third), is characteristic of the paddlefish. Adult paddlefish are completely unscaled. Only the top of the caudal stalk and the fleshy upper caudal fin lobe are covered with ganoid scales . The teeth are tiny. There is a spray hole . On the gill cover there is a large, pointed outgrowth pointing backwards.
Way of life
Paddlefish are active swimmers in the open water of large streams. The paddlefish feeds almost exclusively on plankton , especially small crustaceans - they excrete the food by means of long gill processes . The sexually mature sword sturgeon, on the other hand, begins to eat small fish. The rostrum (the "sword") is apparently used to rummage through the river bed. The spoonbill spawns in groups over rocks and scree in strongly flowing water. The eggs stick to the ground.
Tribal history
In addition to the two current species, some extinct paddlefish are known. Protopsephurus from the Lower Cretaceous of China is the oldest and most primitive paddlefish and sister genus of all others. Paleopsephurus from the Lower and Upper Cretaceous of Montana is the sister genus of the remaining paddlefish. Other extinct paddlefish are Polyodon tuberculata from the lower Paleocene of Montana and Crossopholis from the lower Eocene of Wyoming . All fossil paddlefish also lived in fresh waters.
literature
- Kurt Fiedler: Textbook of Special Zoology, Volume II, Part 2: Fish . Gustav Fischer Verlag, Jena 1991, ISBN 3-334-00339-6 .
- Joseph S. Nelson : Fishes of the World. 4th edition. John Wiley & Sons, Hoboken NJ et al. 2006, ISBN 0-471-25031-7 .
- Peter Bartsch: Actinopterygii, Strahl (en) flosser page 226–240 in Wilfried Westheide & Reinhard Rieger : Special Zoology Part 2: Vertebrae and Skull Animals , 1st edition, Spectrum Academic Publishing Heidelberg • Berlin, 2004, ISBN 3-8274-0307- 3
Web links
- Paddlefish on Fishbase.org (English)