Abstract
Conditions experienced early in life can affect key life-history traits. Individuals that experience a poor nutritional environment early in life can reduce potential costs by delaying sexual maturation. The direct costs of delaying maturation are well known (i.e. delayed onset of breeding), but individuals can also face additional costs as adults. Some of these 'hidden costs' accrue due to cryptic morphological and physiological changes. In mosquitofish (Gambusia holbrooki), males with limited food intake early in life delay maturation to eventually reach a similar adult body size to their well-fed counterparts ('catch-up growth'). Here we tested whether a poor diet early in life incurs hidden costs due to reduced expression of sexually selected male traits (genital size and ejaculate traits). We found that diet early in life significantly influenced sperm reserves and replenishment rate due to age and development-rate dependent effects. Although catching-up in body size ameliorates some of the costs of a poor start in life for males, our findings suggest that long-term fitness costs might arise because of sexually selection against these males. Our results highlight that fitness costs of a poor start in life can extend into adulthood.
