Data from: Sperm longevity and salinity – the overlooked importance of spawning environment for alternative reproductive tactics

Studies on adaptive responses to sperm competition have focused on mating
modes and mating roles. The main mating modes studied are external and
internal fertilization and spermcasting. The focus of male mating roles
assumes one advantageous ‘bourgeois’ role and another disadvantageous
‘parasitic’ role regarding the probability of fertilization. However,
sperm longevity between teleost fishes spawning in hypoosmotic freshwater
and species spawning in hyperosmotic saltwater differs markedly. We argue
that this can have major impacts on sperm adaptations in relation to sperm
competition, due to physiological constraints and different outcomes of
trade-offs. To test this hypothesis, we extracted sperm longevity data
from studies on species with alternative reproductive tactics. We show
that spawning salinity affects sperm longevity by orders of magnitudes and
that this affects the direction in which male tactics differ in sperm
longevity: parasitic males’ sperm lived shorter than bourgeois males’
sperm in freshwater spawners, but longer than bourgeois males’ sperm in
saltwater spawners. These results highlight a need to take spawning
salinity into account in intraspecific as well as interspecies comparisons
of adaptations to sperm competition in external fertilizers.