OSTARIOPHYSAN

any of about 6,000 species of bony fishes belonging to the superorder Ostariophysi, including the majority of freshwater fishes throughout the world. Familiar representatives of this group are the minnows, suckers, characins, loaches, gymnotid eels, and innumerable catfishes. The 31 recognized families of catfishes constitute the order Siluriformes, the remaining 26 families the order Cypriniformes. Humans consume huge quantities of these fishes for food and derive pleasure from the beauty of tropical aquarium fishes. A few harmful species can inflict painful injuries; some others serve as intermediate hosts for parasites of humans. Strange and fascinating behaviour is exhibited by many of these fishesnest building, oral incubation, egg laying in mollusk shells, walking and flying, air breathing, production of sound and electricity, and communication by chemical secretions. any of about 6,000 species of bony fishes belonging to the superorder Ostariophysi. They are grouped into two orders: Cypriniformes (e.g., characins, carps, and minnows) and Siluriformes (catfishes). Ostariophysans form the majority of freshwater fishes. Ostariophysans are distinguished by the Weberian apparatus, the precise function of which is not known. It consists of a chain of four paired bones, called ossicles, derived from the vertebrae immediately behind the skull. These ossicles connect the inner ear and swim bladder, which balances the fish in water. The Weberian apparatus provides a fish with sensitive hearing, as it transmits pressure changes in the water. Ichthyologists often use it to identify various ostariophysan families and orders; among members of the family Gymnotidae (knifefishes), for example, one of the ossicles is missing. Most ostariophysans range in size from 2 to 30 cm (about 1 to 12 inches) long, but the Asian mahseer (family Cyprinidae) attains a length of 2 m (6.5 feet) and a weight of 90 kg (200 pounds). A giant Eurasian catfish called wels grows up to 4.5 m long and weighs up to 300 kg. Many species of ostariophysans provide humans with food, sport, or (as aquarium pets) entertainment. The best-known aquarium pets are the goldfish (Carassius auratus) and common carp (Cyprinus carpio). Ostariophysans generally breed in the spring; the female deposits her eggs in the water, and the male fertilizes them with the milt produced in his testes. Tropical ostariophysans may breed year-round. Some species, such as the catfish, build nests in gravel or sand, while others deposit their eggs under logs or stones or among aquatic plants. Certain species, such as the tigerfish and the piranha of South America, are ferocious and may even prey on humans. Others (e.g., catfish) content themselves with bottom-dwelling. Most ostariophysans feed on phytoplankton, algae, and aquatic vegetation. Additional reading James W. Atz, Dean Bibliography of Fishes 1968 (1971), the first volume of a comprehensive, computerized bibliographic series; George Albert Boulenger, Catalogue of the Fresh-Water Fishes of Africa, 4 vol. (190916, reprinted 4 vol. in 2, 1964), an important, illustrated, systematic account of Old World tropical groups; Philip J. Darlington, Jr., Zoogeography: The Geographical Distribution of Animals (1957, reprinted 1982), an excellent account of the distribution of freshwater fishes; Carl H. Eigenmann and George S. Myers, The American Characidae, 5 pt. (191729), a classic treatise, only one-third completed upon the death of the author; M.M. Ellis, The Gymnotid Eels of Tropical America, Mem. Carneg. Mus., 6:109204 (1914), a comprehensive, systematic, and morphological study; William K. Gregory and G. Miles Conrad, The Phylogeny of the Characin Fishes, Zoologica, 23:319360 (1938), an old, somewhat equivocal, but important contribution on classification; Harry Grundfest, Electric Fishes, Scient. Am., 203:115124 (1960), a semipopular but authoritative article; William T. Innes, Exotic Aquarium Fishes, 20th ed. (1979), a well-illustrated, informative handbook of popular aquarium fishes; John G. Lundberg and Jonathan N. Baskin, The Caudal Skeleton of the Catfishes, Order Siluriformes, Am. Mus. Novit. 2398 (1969), a description of anatomy, evolution, and relationships; W. Pfeiffer, Alarm Substances, Experientia, 19:113123 (1963), an excellent review article; C.T. Regan, The Classification of the Teleostean Fishes of the Order Ostariophysi, Ann. Mag. Nat. Hist., Series 8, 8:1332, 553577 (1911), an old, but historically useful treatise on morphology and classification; John H. Todd, The Chemical Languages of Fishes, Scient. Am., 244:99108 (1971), a description of contemporary experiments on communication; Stanley H. Weitzman, The Osteology of Brycon meeki, a Generalized Characid Fish, with an Osteological Definition of the Family, Stanford Ichthyol. Bull., 8:177 (1962), an important review of characid classification and osteology; Jasper S. Lee, Commercial Catfish Farming, 3rd ed. (1991).