Meeting Abstract
Sperm availability may influence the evolution of gamete traits in broadcast spawners. Gamete characteristics that are advantageous under sperm limiting conditions might be deleterious, as the probability of male-male competition and egg death via polyspermy increases with increasing sperm density. Gamete traits that can modify the sperm-egg collision rate, such as sperm swimming speed and egg size, and those that can modify the sperm-egg fusion rate, such as compatibility between sperm and egg proteins, are known to influence fertilization success. What remains unclear is how these factors interact to influence fertilization success. We utilized no-choice diallel crosses to examine the interactions between sperm swimming ability, egg target size and sperm-egg compatibility on reproductive success under polyspermic and sperm-limiting conditions in the tunicate Ciona intestinalis. Crosses were conducted utilizing two different sperm-egg contact times. To examine the role of sperm-egg compatibility on fertilization success, crossed individuals were sequenced for candidate male and female gamete recognition proteins. A common non-synonymous SNP was identified for both the egg protein in dams and sperm protein in sires. These protein variants were examined for how they interacted to influence fertilization success in statistical models that also incorporated sperm behavior and egg size. Preliminary results indicate that interactions between gamete trait, male genotype, and female genotype can influence fertilization success, and the significance of those interactions is dependent on sperm availability and contact time.
