The effect of parental age on the quantity and quality of offspring inSyngnathus typhle, a species with male pregnancy

Offspring quantity and quality are known to vary according to parental age, with most studies focusing on the mother’s age, who produces costly eggs and often carries out pregnancy, hampering to distinction between trans-generational age effects due to egg quality or physiological deterioration. We investigated the ramification of parental age on the offspring in the broad-nosed pipefish Syngnathus typhle , a fish species with male pregnancy, allowing us to separate these two female traits. By mating parents of different sizes we examined the impact of parental age on offspring number, size and gene expression. Our results show that older parents produced more and larger-sized offspring. However, we revealed intriguing insights into the differential gene expression patterns in offspring, strongly influenced by the paternal lineage but minimally affected by maternal age. Offspring from old fathers exhibited notable changes in gene expression profiles, particularly related to cell cycle regulation, metabolism, protein synthesis, stress response, DNA repair and neurogenesis. Our findings provide valuable insights into the role of pregnancy in shaping offspring physiology. Moreover, we recognize the value of assessing a broader range of species that have evolved with sex-specific differences in parental investment vs. gamete provisioning, as the age of either the mother or father may hold greater significance than the other in influencing offspring fitness.