Independent impacts of age and telomere length on oyster sperm motility

Abstract Aging often goes with the deterioration of gamete quality. However, alteration of male sperm quality alongside age is not univocal between species, and this relationship remains largely elusive in bivalve molluscs. Here, we questioned whether ageing attenuates sperm motility and if telomere length (TL), a marker of individual quality, can further mark sperm performance in the Pacific oysters (Crassostrea gigas). We assessed covariation between sperm motility, age and TL in males (n = 45) from 2 to 9 years old. We replicated the measures at four reproductive sessions, corresponding to two types of maturation conditions (controlled in the lab or natural in the field). We found negative correlations between male age and sperm velocity, and slower sperm in natural conditions compared to controlled ones. TL did not shorten with age, but it was positively associated with sperm velocity while maturing under controlled conditions. Our results underscore that sperm swimming performance decreases with ageing, a relationship identified for the first time in a bivalve species. Further research is needed to understand environmental effects and the predictive aspects of telomere dynamics in covarying with sperm quality.