Aging parasites produce offspring with poor fitness prospects

Abstract

Senescing individuals have poor survival prospects and low fecundity. They can also produce offspring with reduced survival and reproductive success. We tested the effect of parental age on the performance of descendants in the nematode Heligmosomoides polygyrus, an intestinal parasite of rodents. We found that offspring of senescing worms had reduced within-host survival and reduced egg shedding over the first month post-infection compared with offspring produced by young parents. These results suggest that declining offspring quality is a component of senescence in parasitic nematodes and might have evolutionary consequences for the optimal schedule of age-dependent investment into reproductive effort.

Keywords: Heligmosomoides polygyrus; infection; offspring fitness; parental age; senescence.

Figure 1.

Number of adult H. polygyrus worms recovered in the intestinal lumen as a function of worm parental age. Bars indicate mean number of adult at each worm parental age.

Figure 2.

Faecal egg count of H. polygyrus over the first 28 days post-infection for the different worm parental ages. (a) Parental age = 15 days; (b) parental age = 45 days; (c) parental age = 105 days; (d) parental age = 165 days. Bars indicate mean number of eggs at each worm parental age.