Boschung, Herbert T. Formerly, Department of Biological Sciences, University of Alabama, Tuscaloosa, Alabama.
- Tribe Thunnini
- Tribe Sardini
- Additional Readings
Certain perciform (spiny-rayed) fishes in the family Scombridae. Like all other scombrids (such as mackerels, bonitos, wahoo, and sierras), tunas have a fusiform (tapering toward each end) and moderately compressed body and certain other characteristics that adapt them for sustained swimming at high speeds. The long spinous dorsal fin is depressible in a groove in the back; the pelvic fins and usually the pectoral fins are small and retractable in shallow depressions; the scales are typically small, but enlarged scales usually cover the anterior part of the body and lateral line, and form an envelopment called the corselet. The eyes protrude very little, if at all, beyond the surface of the head; the mouthparts fit snugly against the pointed head; and the gill covers fit snugly against the body. These features eliminate almost all irregularities that would cause resistance to the water. Tunas are also recognized by the finlets (independent multibranched rays, each appearing as a small fin) behind the dorsal and anal fins. The slender caudal peduncle, supported on each side by two small keels and a large median keel in between, and the lunate caudal fin are driven by powerful muscles for fast and sustained swimming. Sustained swimming depends on red muscle (comparatively thin muscle fibers containing large amounts of myoglobin and mitochondria), and the body temperature of tunas may be several degrees above water temperature. Tunas feed on a wide variety of fishes, squids, and crustaceans. See also: Muscular system; Perciformes
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