[
International Worm Meeting,
2021]
Aging in C. elegans is unusual in terms of the severity and early onset of senescent pathology, particularly affecting organs involved in reproduction (1-3). For example, in post-reproductive hermaphrodites, intestinal biomass is converted into yolk leading to intestinal atrophy and yolk steatosis (3). While such post-reproductive yolk production has long been viewed as futile (1,4), we wondered if it could somehow promotes fitness. We report that sperm-depleted hermaphrodites vent copious amounts of yolk through the vulva. This yolk can be consumed by larvae and promote their growth. This implies that post-reproductive mothers can continue to contibute to reproductive fitness by converting their biomass into a substance that serves a similar function to milk. This suggests that gut atrophy is a cost of a form of primitive lactation (also seen in certain insects). Moreover, unfertilized oocytes function as vectors carrying yolk to larvae. This type of massive reproductive effort involving biomass repurposing that causes organ degeneration is characteristic of semelparous organisms (i.e. that exhibit only a single reproductive episode) ranging from monocarpic plants to Pacific salmon, where it frequently leads to rapid death (reproductive death). We also observed yolk venting in hermaphrodites of other Caenorhabditis species and in Pristionchus pacificus hermaphrodites, but not in females of either genus. Moreover, females do not exhibit gut atrophy or steatosis and are longer lived, suggesting absence of reproductive death. Furthermore, across species germline ablation strongly increases lifespan in nematode hermaphrodites but not females; similarly, in diverse animal and plant species blocking sexual maturation e.g. by gonadectomy frequently causes large increases in lifespan in organisms that undergo reproductive death, but not in those that don't. Insulin/IGF-1 signaling, which accelerates C. elegans aging, also promotes yolk production and gut atrophy (1,3). These results suggest that C. elegans hermaphrodites exhibit reproductive death, suppression of which increases lifespan. If correct, this has significant implications in terms of what one can learn about human aging from C. elegans. (1) Nature 2002 419: 808. (2) Genetics 2002 161: 1101. (3) Curr. Biol. 2018 28: 2544. (4) BMC Physiol. 2011 11: 11.