Fasting increases investment in soma upon refeeding at the cost of gamete quality in zebrafish

Fasting increases lifespan in invertebrates, improves biomarkers of health
in vertebrates, and is increasingly proposed as a promising route to
improve human health. Nevertheless, little is known about how fasted
animals use resources upon refeeding, and how such decisions affect
putative trade-offs between somatic growth and repair, reproduction, and
gamete quality. Such fasting-induced trade-offs are based on strong
theoretical foundations and have been recently discovered in
invertebrates, but the data on vertebrates is lacking. Here we report that
fasted female zebrafish, Danio rerio, increase investment in soma upon
refeeding, but it comes at a cost of egg quality. Specifically, an
increase in fin re-growth was accompanied by a reduction in 24-hours
post-fertilization offspring survival. Refed males showed a reduction in
sperm velocity and impaired 24-hour post-fertilisation offspring survival.
These findings underscore the necessity of considering the impact on eggs
and sperm when assessing evolutionary and biomedical implications of
lifespan-extending treatments in females and males and call for careful
evaluation of the effects of fasting (both during and post) on
fertilisation.