Experimental evidence that litter size imposes an oxidative challenge to offspring

Abstract

The post-natal environment in which young develop can substantially impact development, adult phenotype and fitness. In wild mice, competition among litter-mates affects development rate and adult behaviour. We manipulated post-natal litter size in a cross-fostering design to investigate the effects of enlarged and reduced litter sizes on sexual signalling, oxidative stress and the links between them. Oxidative stress causes somatic damage that can limit reproductive success and lifespan, and is predicted to mediate investment in life-history traits, including sexual signals. We predicted that litter enlargement would cause an increase in potential oxidative stress, inhibit growth and reduce sexual signalling in male mice. Males reared in enlarged litters were smaller at weaning and, despite rapid growth immediately after weaning, remained smaller at 10 weeks of age than those reared in smaller litters. Females from enlarged litters were consistently smaller throughout post-weaning development and showed no increase in growth rate compared with females from reduced litters. In enlarged litters, protein thiol concentration was lower at weaning in the liver and kidneys, with this trend continuing at 10 weeks of age in the kidneys only. Aconitase enzyme activity was also lower in mice from enlarged litters at weaning and 10 weeks of age in the kidneys. Male mice from enlarged litters scent marked more frequently and had larger preputial glands than those from reduced litters, indicating greater sexual signalling investment irrespective of this increased oxidative challenge. The results of this study are the first to reveal oxidative costs of developmental stress in small mammals.

Limits to sustained energy intake XXVII: trade-offs between first and second litters in lactating mice support the ecological context hypothesis

“…An additional impact may be experienced by their offspring. We found that the offspring raised in reduced and enlarged litters differed significantly in their body mass, and poor early nutrition has been previously linked to impairment of performance and reduced survival in several species (Gibson et al, 2015;Plumel et al, 2014). In line with these previous suggestions, we found that pup mass at weaning was reduced in females from enlarged litters compared with females from reduced Day of lactation at which measurements were taken is indicated for each variable.…”

Perceived threats of infanticide reduce maternal allocation during lactation and lead to elevated oxidative damage in offspring

“…At 13 weeks of age, half of the female and male offspring from the novel male and familiar male treatment groups were culled humanely by cervical dislocation, and the liver, kidney, heart and gastrocnemius muscle were quickly removed, snap‐frozen in liquid nitrogen and stored at −80°C. To assess oxidative stress in the mice, two biomarkers of oxidation including protein thiol content and aconitase enzyme activity were analysed in each of the tissues (Gibson, Garratt & Brooks, ). Both of these biomarkers correlate negatively with oxidative stress.…”

Development of homeothermic endothermy is delayed in high-altitude native deer mice ( Peromyscus maniculatus)

“…However, despite large litter sizes, we observed that HA pups maintained similar growth rates to LA pups. While mothers in our study were fed ad libitum, larger litter sizes should still increase intra-litter competition for milk [56]. If HA pups are nutrient limited owing to increased competition from litter mates, then suppressing energetically costly thermogenesis may help them recoup some of their energetic costs in favour of maintaining growth rates even in normoxia.…”