Quantitative Study of the Adult Male Dentition of the Red-Backed Salamander, Plethodon cinereus

Abstract

Although the qualitative features of the teeth of plethodontid salamanders have been described in considerable detail by several authors (Wake, 1966; Duellman and Trueb, 1986; Atwill and Trauth, 1988; and references therein), there have been relatively few studies that have examined quantitatively plethodontid salamander dentition (but see Stewart, 1958; Highton, 1962; Coss, 1974). Data on tooth size and number are available only for the two-lined salamander Eurycea bislineata (Stewart, 1958) and several species of Plethodon (Highton, 1962; Coss, 1974). The relationship between tooth number and body size has been explored only for vomerine teeth in several species of Plethodon (Highton,1962). No study has addressed the relationships between body size and the size and number of the teeth on all tooth-bearing bones for any plethodontid species. We investigated the relationships between tooth size and number and body size in Plethodon cinereus, a salamander that has been hypothesized to use its teeth in foraging (Regal, 1966; Duellman and Trueb, 1986), courtship (Arnold, 1972), and fighting (Thurow, 1976; Jaeger and Forester, 1993; Mathis et al., 1995). Thurow (1976) hypothesized that large size advantage in agonistic contests may be related directly to relative tooth size, that is, larger individuals have larger teeth. The possession of larger and more numerous teeth by larger individuals may also explain observed female preferences for males of large body size (Mathis, 1991). To control for factors such as age, sex, and population of origin, we studied only adult male P cinereus from a single population at Mountain Lake Biological Station, Virginia. The dentition of males unlike that of females varies seasonally (Stewart, 1958; Coss, 1974); therefore, we also examined the relationship between the season of collection and tooth number and qualitatively compared the shapes of the teeth of salamanders from our study with published descriptions (Moury et al., 1985, 1987). In P cinereus, teeth are replaced continously throughout life in a process termed zahnreihen (Lawson et al., 1971). At any one time during the life of the salamander, several loci may be either empty or contain teeth that are not yet fully functional. In our analysis, we counted and measured only teeth that were fully functional (the crown fully exposed above the oral mucosa).