Data from: Ovarian fluid allows directional cryptic female choice despite external fertilization

In species with internal fertilization, females can favour certain males
over others, not only before mating but also within the female’s
reproductive tract after mating. Here, we ask whether such directional
post-mating (that is, cryptic) female mate choice can also occur in
species with external fertilization. Using an in vitro sperm competition
experiment, we demonstrate that female ovarian fluid (ovarian fluid)
changes the outcome of sperm competition by decreasing the importance of
sperm number thereby increasing the relative importance of sperm velocity.
We further show that ovarian fluid does not differentially affect sperm
from alternative male phenotypes, but generally enhances sperm velocity,
motility, straightness and chemoattraction. Under natural conditions,
female ovarian fluid likely increases the paternity of the preferred
parental male phenotype, as these males release fewer but faster sperm.
These results imply females have greater control over fertilization and
potential to exert selection on males in species with external
fertilization than previously thought possible.