Wild Atlantic cod sperm motility is negatively affected by ovarian fluid of farmed females

Abstract

Atlantic cod escape from fish farms at higher rates than commonly cultured marine species, and escapees have been observed to interact with wild fish in mating aggregations. Previous research suggests that potential interbreeding is mediated largely by the likelihood of wild males spawning with escaped females, and as such, the egg and ovarian fluid characteristics of these females could affect fertilization success and the likelihood of hybridization. Farmed cod have been noted to have poor egg quality compared to wild individuals, and some of this difference may be due to the ovarian fluid, which can affect key sperm-motility parameters related to fertilization success. We tested the hypothesis that the ovarian fluid of farmed females negatively affects the sperm performance of wild males. Sperm-motility parameters and fertilization capacity of wild male sperm were analyzed in the presence of both farmed and wild female ovarian fluid. Sperm performed similarly in the presence of wild female ovarian fluid and a seawater control. Ovarian fluid of farmed females negatively affected sperm swimming and the capacity to fertilize eggs. These differences may be related to nutritional deficiencies of farmed individuals. Although it has been demonstrated that wild males actively court farmed females, our results indicate that their ovarian fluid quality can inhibit fertilization success.

Assessing risks of invasion through gamete performance: farm Atlantic salmon sperm and eggs show equivalence in function, fertility, compatibility and competitiveness to wild Atlantic salmon

“…Although we compared sperm function in river water, without additional ovarian fluid manipulations which can influence motility (e.g. Yeates et al 2013, Beirão et al 2014, our fertilization and sperm competition trials were run in the presence of either strain's ovarian fluid on their eggs, and therefore, these findings do account for any influence of ovarian fluid on reproductive performance. Moreover, comparisons of our hatchery-reared fish with Atlantic salmon that were born and raised in the wild reveal similarities in sperm densities and sperm length.…”

Freezing ovarian fluid does not alter how it affects fish sperm swimming performance: creating a cryptic female choice ‘spice rack’ for use in split‐ejaculate experimentation

“…Sperm cryopreservation is used to achieve fertilizations at a desired time, but generally alters sperm swimming performance ( e.g ., Butts et al ., ) and is thus problematic if the goal is to assess subtle sperm responses to female cues. Studies sometimes refrigerate OF for a few hours or days ( e.g ., Yeates et al ., ) or freeze it ( e.g ., Beirão et al ., , ). These OFs can then be tested with freshly collected semen.…”

“…Studies sometimes refrigerate OF for a few hours or days (e.g., Yeates et al, 2013) or freeze it (e.g., Beirão et al, 2014Beirão et al, , 2015. These OFs can then be tested with freshly collected semen.…”

Sperm performance in conspecific and heterospecific female fluid

“…), and the concentration of various ions, which can have species‐specific effects (birds: Wishart and Wilson ; fish: Beirão et al. ). After crossing the vagina, species‐specific barriers could also occur while sperm are stored in the female's sperm storage tubules and/or when sperm interact with the ovum at the point of fertilization, although current evidence suggests these barriers may be relatively weak compared to the vaginal barrier (Bakst et al.…”