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fish that give birth to more or less completely formed young fry, as distinguished from fish that spawn eggs. Most selachii (the majority of sharks, stingrays, eagle rays, and giant rays) are viviparous fish. Among bony fish, viviparity is a characteristic of eelpouts (Zoarces viviparus], bass (Sebastes), Baikal oil-fish (Comephorus baicalensis), many fish of the family Cyprinodontidae (four-eyed fish— Anableps tetrophthalmus], and some freshwater fish of the family Hemirhamphidae.
Fertilization of all viviparous fish is internal. In strictly viviparous fish the embryo is attached to and nourished by the mother’s body (for example, the smoothhound). In ovoviviparous fish, which comprise the majority of viviparous fish, the ova are in the mother’s body but are not connected to it. The ova of these fish develop by feeding on the yolk. The developmental period of the fry in the ovaries or in modified oviducts ranges from two or three weeks in cyprinodonts to several months in sharks. Sharks give birth to one or several large fry, measuring up to 70 cm long. Most bony fish bear tens or hundreds of fry—for example, the Murmansk sea bass gives birth to as many as 350,000 small larvae, measuring up to 8 mm long. Viviparous fish of the family Poecilidae, such as guppies and swordtails, are raised in aquariums.
A. A. SVETOVIDOVA