paddlefish(redirected from Polyodontid)
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paddlefish,large freshwater fish, Polyodon spathula, of the Mississippi valley, also called spoonbill or duckbill and named for its flattened, paddle-shaped snout. The largest specimens weigh well over 150 lb (67.5 kg) and reach 6 ft (183 cm) in length. The snout may be a third of the length of the body; it is equipped with sense organs that assist the fish in finding its prey of small crustaceans, which it strains out with gill rakers (see gillgills,
external respiratory organs of most aquatic animals. In fishes the gills are located in gill chambers at the rear of the mouth (pharynx). Water is taken in through the mouth, is forced through openings called gill slits, and then passes through the gill clefts, spaces
..... Click the link for more information. ). Paddlefishes are primitive; unlike most modern fishes, they have skins with reduced scales, almost wholly cartilaginous skeletons, and upturned tail fins. They are uniform leaden gray in color. Valued as food fish, their greenish black eggs, like the more highly valued ones of the distantly related sturgeonsturgeon,
primitive fish of the northern regions of Europe, Asia, and North America. Unlike evolutionarily advanced fishes, it has a fine-grained hide, with very reduced scalation, a mostly cartilaginous skeleton, upturned tail fins, and a mouth set well back on the underside of
..... Click the link for more information. , are used to make caviarcaviar
, the roe (eggs) of various species of sturgeon prepared as a piquant table delicacy. The ovaries of the fish are beaten to loosen the eggs, which are then freed from fat and membrane by being passed through a sieve.
..... Click the link for more information. . A Chinese species, Psephurus gladius, found in the Chang (Yangtze) River but now on the verge of extinction is reported to grow some 20 ft (6 m) in length. Paddlefishes are classified in the phylum ChordataChordata
, phylum of animals having a notochord, or dorsal stiffening rod, as the chief internal skeletal support at some stage of their development. Most chordates are vertebrates (animals with backbones), but the phylum also includes some small marine invertebrate animals.
..... Click the link for more information. , subphylum Vertebrata, class Actinopterygii, order Acipenseriformes, family Polyodontidae.
(Polyodontidae), a family offish of the order Acipenseriformes. The skin of the paddlefish is bare or covered with small bony scales. The snout is broad, flat, long, and shaped like a paddle or sword. The jaws are armed with numerous small teeth. There are two genera, including two modern and two fossil species. The species Polyodon spathula is found in the Mississippi River, Lake Erie, and rivers in the southern USA. They are up to 2 m long and weigh up to 75 kg. They feed on worms, water insects, crustaceans, and water plants and breed from March to June. Paddlefish have local commercial significance. The species Psepherus gladius is found in China (in the Yangtze River). They are up to 7 m long. They are predators and have little commercial significance.
REFERENCENikol’skii, G. V. Chastnaia ichtiologiia, 2nd ed. Moscow, 1954.
G. I. LINDBERG