ATHERINIFORM

California flying fish (Cypselurus californicus) any member of the order Atheriniformes, a group of bony fishes comprising such well-known marine forms as the flying fish (see photograph) as well as numerous freshwater species. Members of the suborder Exocoetoidei, which includes the flying fishes, halfbeaks, needlefishes, and sauries, are slender, elongated fish less than 1 m (3 feet) in length. The eggs of most species have adhesive filaments by which they adhere to aquatic plants. The dorsal and anal fins are set opposite each other and far back on the body. The suborder Cyprinodontoidei consists of small, surface-oriented, omnivorous fishes with complex courtship and spawning patterns. They are highly adaptable and are able to tolerate extremes of heat, drought, and salinity. These fishes (e.g., killifishes) are sometimes called topminnows, or toothed carp, because of the small teeth in their jaws. They have yearly life cycles, and the adults, before dying during the summer, leave behind eggs buried in the mud. With the return of the rain these eggs hatch, and the life cycle is repeated. The two species of four-eyed fish among the Cyprinodontoidei are uniquely adapted to surface living. Their eyes are divided into upper and lower lobes with separate corneas and retinas so that they can see both above and below the water. Males and females have sex organs oriented either to the right or left. Because of this distinction, sinistral males can mate only with dextral females, and vice versa. In the live-bearers among the Cyprinodontoidei, the anal fins of the male have been modified into a copulatory organ called the gonopodium. Many species, including the guppies, mollies, and swordtails, give birth to live young. Fishes that belong to the suborder Atherinoidei are small and elongated, with large eyes and two dorsal fins. This suborder includes the silversides, which are characterized by large silver scales and travel in schools near the shores of oceans and lakes. One of the best-known species of Atherinoidei is the California grunion (Leuresthes tenuis). Each spring and sometimes long into the summer, these fish come out of the water to spawn during the full moon. During high tide, the grunions leave their eggs buried in the sand of the beaches. At the next high tide, about two weeks later, the young are swept out to sea. California flying fish (Cypselurus californicus) any member of the order Atheriniformes, containing 15 families of marine and freshwater spiny-finned fishes, including the flying fishes (see photograph), needlefishes, silversides, and cyprinodonts. The last group, the Cyprinodontidae, is an abundant tropical and subtropical family that includes the guppies, mollies, swordtails, and many other aquarium fishes. In addition to the Atheriniformes, this article treats the three smaller related orders Beryciformes, Zeiformes, and Lampridiformes, the most primitive groups of the superorder Acanthopterygii, or spiny-finned fishes. Additional reading R.M. Alexander, Mechanisms of the Jaws of Some Atheriniform Fish, J. Zool., 151:233255 (1967), an account of methods of jaw protrusion; C.M. Breder and D.E. Rosen, Modes of Reproduction in Fishes (1966), especially good on reproductive modifications in atheriniforms, with a full bibliography; D.S. Jordan and C.L. Hubbs, A Monographic Review of the Family Atherinidae or Silversides, Stanford Univ. Publs., Univ. Ser., Studies in Ichthyology, 1:187 (1919), a classic review of atherinoids; C.T. Regan, On the Anatomy, Classification, and Systematic Position of the Teleostean Fishes of the Suborder Allotriognathi, Proc. Zool. Soc. Lond., pp. 634643 (1907), a classic paper in which the lampridiforms were first grouped together; R.R. Rofen, The Whale-Fishes: Families Cetomimidae, Barbourisiidae and Rondeletiidae (order Cetunculi), Galathea Rep., 1:255260 (1959), an illustrated account of these deep-sea forms; D.E. Rosen, The Relationships and Taxonomic Position of the Halfbeaks, Killifishes, Silversides and Their Relatives, Bull. Am. Mus. Nat. Hist., 127:219267 (1964), a monograph, with a bibliography, in which the Atheriniformes were first grouped together, and with R.M. Bailey, The Poeciliid Fishes (Cyprinodontiformes), Their Structure, Zoogeography, and Systematics, ibid., 126:1176 (1963), a monographic account of peociliids, and with C. Patterson, The Structure and Relationships of the Paracanthopterygian Fishes, ibid., 141:359474 (1969), discussions of the relationships of fossil and living beryciforms, lampridiforms, and atheriniforms, with a bibliography.