Parental age effects on body size and growth rate in guppy-fish

We analysed the effect of parental ageing on variations in body size and growth rate of guppy-fish progeny. The resulting data showed that the mean body length of the progeny increases with advancing parental age and this increase might be due to a faster growth rate of progeny from older parents. Given the high correlation linking parental age and maternal size, the involvement of size cannot be ruled out, even though parental age had a greater effect than maternal size on the body length of progeny in one of the two populations considered. Variation in progeny growth rate in relation to variation in parental age might be due to an adaptive mechanism which allows the offspring of older parents to reach reproductive age faster.