Tooth Replacement in King Mackerel, Scomberomorus cavalla (Pisces: Scombridae)

Abstract

Tooth formation and replacement were analyzed in 41 specimens of Scomberomorus cavalla. Teeth of this species are laterally compressed blades adapted for cutting action on prey. Development of each tooth begins at the tip and proceeds toward the base. New tooth buds form in a resorption cavity in the base of an older tooth. Resorption occurs at two points on each tooth: in the base and in the anterior-posterior edges just above the jawline. Teeth pass through seven stages of develop- ment and resorption, but remain longest in the preeruptive and primary functional stages. Replace- ment occurs in overlapping waves in alternate tooth loci. Replacement waves may be flat, progress from the rear to front, or progress front to rear. Most replacement data can be adapted to either the Zahnreihen concept of Edmund (1960, 1969) or the tooth family concept of Osborn (1971, 1972, 1974). One tooth germ failure, causing the crossing of replacement waves, is noted. Polyphyodont tooth replacement in lower vertebrates was summarized by Edmund (1960, 1969), who primarily considered reptilian dentitions, but made a few observations on other groups. He proposed that tooth replacement in all polyphyodont dentitions was regulated by a series of stimuli passing caudad along the dental lamina producing tooth germs at each locus. He demonstrated that the interval between successive stimuli determined the direction in which replacement waves, operating in alternate tooth loci, would progress. Edmund used the term Zahnreihen to indicate the teeth produced by a single stimulus. When depicted graphically, Zahnreihen appear as obliquely running lines connecting teeth in adjacent loci. Edmund demonstrated that if Zahnreihen producing stimuli pass down the dental lamina at intervals of 2.0 tooth posi- tions, simple alternate replacement will result. If stimuli are produced at inter- vals greater than two tooth positions, rear to front waves are produced. When stimuli occur at intervals of less than two tooth positions, fron to rear waves are produced. Lawson, et al. (1971) presented a theoretical analysis of variations in replacement waves produced by different Zahnreihen spacings. Osborn (1971, 1972, 1974) rejected the Zahnreihen concept in favor of the tooth family concept. His findings, based primarily on studies of Lacerta vivipara, suggest that tooth replacement is regulated by a sphere of inhibition surround- ing developing teeth and extending into adjacent loci. Since a developing tooth temporarily inhibits tooth development in adjacent loci, adjacent teeth are always in different stages of development. Gillette (1955) first suggested such a sphere of inhibition around the developing teeth of Rana pipiens. Osborn (1971, 1974) suggested that tooth initiation, and initiation of rear to front replacement, is caused by the invasion of neural crest cells from the caudal end of the jaw bone. Some previous studies of tooth replacement in bony fishes include: Norris and Prescott (1959) studied replacement in Girella nigricans; Roberts (1967) surveyed many of the characoid genera; Lawson and Manly (1973) studied an additional characoid species Ctenolucius hujeta; Miller and Radnor (1973) investigated the holostean Amia calva; and Wakita, et al. (1977) reported on tooth replacement in