Maternal age effects on fecundity and offspring egg-to-adult viability are not affected by mitochondrial haplotype

Transcriptional memory of dFOXO activation in youth curtails later-life mortality through chromatin remodeling and Xbp1

A transient, homeostatic transcriptional response can result in transcriptional memory, programming subsequent transcriptional outputs. Transcriptional memory has great but unappreciated potential to alter animal ageing as animals encounter a multitude of diverse stimuli throughout their lifespan. Here we show that activating an evolutionarily conserved, longevity-promoting transcription factor, dFOXO, solely in early adulthood of female fruit flies is sufficient to improve their subsequent health and survival in mid- and late life. This youth-restricted dFOXO activation causes persistent changes to chromatin landscape in the fat body and requires chromatin remodellers such as the SWI/SNF and ISWI complexes to program health and longevity. Chromatin remodelling is accompanied by a long-lasting transcriptional programme that is distinct from that observed during acute dFOXO activation and includes induction of Xbp1. We show that this later-life induction of Xbp1 is sufficient to curtail later-life mortality. Our study demonstrates that transcriptional memory can profoundly alter how animals age.

Age of Both Parents Influences Reproduction and Egg Dumping Behavior in Drosophila melanogaster

Trans-generational maternal effects have been shown to influence a broad range of offspring phenotypes. However, very little is known about paternal trans-generational effects. Here, we tested the trans-generational effects of maternal and paternal age, and their interaction, on daughter and son reproductive fitness in Drosophila melanogaster. We found significant effects of parent ages on offspring reproductive fitness during a 10 day postfertilization period. In daughters, older (45 days old) mothers conferred lower reproductive fitness compared with younger mothers (3 days old). In sons, father’s age significantly affected reproductive fitness. The effects of 2 old parents were additive in both sexes and reproductive fitness was lowest when the focal individual had 2 old parents. Interestingly, daughter fertility was sensitive to father’s age but son fertility was insensitive to mother’s age, suggesting a sexual asymmetry in trans-generational effects. We found the egg-laying dynamics in daughters dramatically shaped this relationship. Daughters with 2 old parents demonstrated an extreme egg dumping behavior on day 1 and laid >2.35× the number of eggs than the other 3 age class treatments. Our study reveals significant trans-generational maternal and paternal age effects on fertility and an association with a novel egg laying behavioral phenotype in Drosophila.

Transgenerational maternal age effects in nature: Lessons learnt from Asian elephants

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Reichert, S., Berger, V., Jackson, J., Chapman, S. N., Htut, W., Mar, K. U., & Lummaa, V. (2019). Maternal age at birth shapes offspring life-history trajectory across generations in long-lived Asian elephants. Journal of Animal Ecology, 89, 996-1007. Parental age can have strong effects on offspring life history, but the prevalence and magnitude of such effects in natural populations remain poorly understood. Using a multigenerational dataset of semi-captive Asian elephants, Reichert et al. (2019) studied the effects of maternal and grandmaternal age on offspring performance and found that offspring from old mothers have lower survival, but higher body condition and reproductive success than offspring from younger mothers. Importantly the observed consequences on survival are long-lasting and span more than one generation, with grand-offspring of old grandmothers also showing reduced survival. These findings suggest that persistent transgenerational effects of maternal age on fitness can shape the individual variation in ageing patterns in nature and ultimately the evolution of life histories.

Parental breeding age effects on descendants' longevity interact over 2 generations in matrilines and patrilines

Individuals within populations vary enormously in mortality risk and longevity, but the causes of this variation remain poorly understood. A potentially important and phylogenetically widespread source of such variation is maternal age at breeding, which typically has negative effects on offspring longevity. Here, we show that paternal age can affect offspring longevity as strongly as maternal age does and that breeding age effects can interact over 2 generations in both matrilines and patrilines. We manipulated maternal and paternal ages at breeding over 2 generations in the neriid fly Telostylinus angusticollis. To determine whether breeding age effects can be modulated by the environment, we also manipulated larval diet and male competitive environment in the first generation. We found separate and interactive effects of parental and grand-parental ages at breeding on descendants' mortality rate and life span in both matrilines and patrilines. These breeding age effects were not modulated by grand-parental larval diet quality or competitive environment. Our findings suggest that variation in maternal and paternal ages at breeding could contribute substantially to intrapopulation variation in mortality and longevity.

Inbreeding depression causes reduced fecundity in Golden Retrievers

Inbreeding depression has been demonstrated to impact vital rates, productivity, and performance in human populations, wild and endangered species, and in recent years, the domestic species. In all cases, standardized, high-quality phenotype data on all individuals are invaluable for longitudinal analyses such as those required to evaluate vital rates of a study cohort. Further, many investigators agree upon the preference for and utility of genomic measures of inbreeding in lieu of pedigree-based estimates of inbreeding. We evaluated the association of measures of reproductive fitness in 93 Golden Retrievers enrolled in the Golden Retriever Lifetime Study with a genomic measurement of inbreeding, F_ROH. We demonstrate a statistically significant negative correlation between fecundity and F_ROH. This work sets the stage for larger scale analyses to investigate genomic regions associated with fecundity and other measures of fitness.

Life History Effects Linked to an Advantage for wAu Wolbachia in Drosophila

Wolbachia endosymbiont infections can persist and spread in insect populations without causing apparent effects on reproduction of their insect hosts, but the mechanisms involved are largely unknown. Here, we test for fitness effects of the wAu infection of Drosophila simulans by comparing multiple infected and uninfected polymorphic isofemale lines derived from nature. We show a fitness advantage (higher offspring number) for lines with the wAu Wolbachia infection when breeding on grapes, but only where there was Talaromyces and Penicillium fungal mycelial growth. When breeding on laboratory medium, the wAu infection extended the development time and resulted in larger females with higher fecundity, life history traits, which may increase fitness. A chemical associated with the fungi (ochratoxin A) did not specifically alter the fitness of wAu-infected larvae, which developed slower and emerged with a greater weight regardless of toxin levels. These findings suggest that the fitness benefits of Wolbachia in natural populations may reflect life history changes that are advantageous under particular circumstances, such as when breeding occurs in rotting fruit covered by abundant mycelial growth.