Growth of Larval and Juvenile Newts

In smooth newts (Triturus vulgaris), adult body size is determined by mainly by growth during the pre-maturity stages. Adult body size is frequently related to reproductive success and hence fitness. This project examined factors affecting growth during the prematurity stages. Chapter 2 reviews the literature on the effects of adult body size on reproductive success in urodeles with particular reference to newts of the Triturus genus. This review identifies the need to experimentally test and further quantify body size effects. Two such studies are reported in Chapter 3. Chapter 3 examines the relationship between female body size and fecundity in female smooth newts and also examines short-term mating capacity in males. Female body size is strongly related to fecundity but there is only a weak relationship between male body size and the number of spermatophores deposited. Chapter 4 describes the pattern of growth of newt larvae (T. alpestris, T. cristatus and T. vulgaris) grown in the laboratory. Variation in larval period explains most of the body size variation at transformation. Chapters 5, 6 and 7 report studies investigating the effects of temperature, food availability, larval density, maternal effects, population effects and timing of oviposition on the growth of T. vittatus and T. vulgaris larvae in the laboratory and semi-natural conditions. Chapter 8 investigates growth during the eft stages of T. cristatus and T. vulgaris. The rank ordering of body sizes of individuals at transformation is preserved during the eft stage in T. vulgaris and T. cristatus, and to adulthood in T. cristatus. Variability between growth strategies of individual newts may have been naturally selected as a response to larval life in a variable and unpredictable environment.