Reproductive Modes and the Number and Sizes of Ova in the Urodeles

Three major reproductive modes are described among the salamanders, one associated with abandoning the eggs in still waters, another with nesting in running waters, and a third with direct development in terrestrial sites. Correlations are examined between adult body size, ovum size, clutch size, hatchling size, and metamorphic size. All are found to be interrelated. Very simply, larger animals produce larger ova and more of them per reproductive cycle and, furthermore, metamorphose at larger larval sizes. Larger ova result in larger hatchlings regardless of reproductive mode. These data are examined in the light of theoretical considerations concerning the kinds of selection pressures that can operate on ovum and clutch size.