Maternal effects associated with gestation conditions in a viviparous lizard, Niveoscincus metallicus

Viviparous squamates offer opportunities for exploring the importance of past maternal resources (yolk) and current resources (placentotrophy) to support embryonic growth during gestation, and to optimize offspring fitness. Both thermal and nutritional environment of the mother during gestation may be expected to be important in determining offspring fitness. Using a two-way factorial design, we have investigated possible interactions between food intake and thermal environment during gestation in the viviparous skink Niveoscincus metallicus. Among the females given restricted basking opportunities, fewer females gave birth, there was a significant increase in gestation length, and relative clutch mass was reduced due to smaller neonatal size; none of these parameters were influenced by nutritional status. Neonates from mothers given restricted basking opportunities were lighter, had shorter snout-vent lengths (SVL), and smaller fat bodies than neonates from mothers given optimal basking opportunities; their postnatal growth rate (over eight weeks) was also significantly lower and they showed a reduced incidence of basking behavior. There were interaction effects between thermal regime and food supply for neonate SVL and neonatal fat body weight. Sprint speed within 24 hours of birth was significantly increased in neonates from mothers given restricted thermal opportunities; however, for weeks 1-8 postnatally, there were no differences in sprint speed in offspring from any of the treatments. These results suggest that, contrary to our initial hypothesis, females maintained in nutritionally favorable conditions are unable to compensate for the gestational effects of a thermally poor environment. We now suggest that in Niveoscincus metallicus facultative placentotrophy may allow mothers to improve offspring fitness by increasing neonatal fat body size.