Effect of age on the fecundity and sperm morphology of the nematode, Teratorhabditis palmarum Gerber and Giblin-Davis, 1990

Ageing in nematodes is associated with a progressive decline in reproductive performance and alterations in gamete morphology. In this study, we examined the effects of age on fecundity and sperm morphology in an amphimictic nematode, Teratorhabditis palmarum . Egg production and progeny output were recorded for young and ageing males and females across the reproductive period, alongside measurements of sperm size and structural integrity. Young females mated with ageing males produced 147 progeny/day on day 1 and 124 progeny/day on day 2, followed by a significant decline to 10 progeny/day by day 5. Similarly, ageing females mated with young males exhibited rapid reductions in fecundity, with egg-laying ceasing by day 9. Sperm from males up to 6 days old measured 9–12 μ m in diameter but decreased to 7–11 μ m thereafter, accompanied by increased morphological abnormalities such as surface roughness. These changes are consistent with previously reported age-associated declines in sperm competitiveness, motility and fertilisation efficiency. Our findings highlight that reproductive ageing in T. palmarum involves both quantitative reductions in progeny production and qualitative deterioration in sperm morphology, suggesting that sperm size and integrity are critical contributors to age-related declines in reproductive success.