Sperm traits in Chinook salmon depend upon activation medium: implications for studies of sperm competition in fishes

Abstract

Sperm traits of externally fertilizing fish species are typically measured in fresh (or salt) water, even though the spawning environment of their ova contains ovarian fluid. In this study, we measured sperm traits of Chinook salmon ( Oncorhynchus tshawytscha (Walbaum in Artedi, 1792)) in both fresh water and dilute ovarian fluid at 10 and 20 s postactivation, using a computer-assisted sperm analysis system. Spermatozoa swam faster, and had both higher percent motility and a straighter path trajectory for a longer period of forward motility when activated in ovarian fluid compared with activation in fresh water. Comparing sperm activity of 10 males in water versus ovarian fluid, we found a weak but significant correlation for sperm swimming speed at 10 s postactivation (r = 0.34, p = 0.01), but not for any other sperm traits measured. Most important, across males, mean sperm swimming speed in water accounted for <10% of the observed variation in mean sperm swimming speed in ovarian fluid. Thus, we argue that sperm traits measured in fresh water are not particularly relevant to those same traits during normal spawning in this species. We suggest that sperm performance measured in fresh water should be used with caution when comparing the potential for individual males to fertilize ova, especially in studies of sperm competition in externally fertilizing species.

Ejaculate Allocation and Sperm Competition in Alternative Reproductive Tactics of Salmon and Trout: Implications for Aquaculture

“…100-300 s at 2-4 Cº (Vladić & Järvi 1997). Salmon parr have greater sperm vigour (percentage of motile cells in ejaculates) (Vladić & Järvi 2001) and trade-off between sperm velocity and longevity after one-third of time since sperm activation (Vladić 2001), the result in agreement with the result published by Levitan (2000) (see Rosengrave et al 2009 for the discussion of effect of ovarian fluid on sperm behaviour). Therefore, studies on sperm traits should not imply contention of individual male quality unless these traits are tested in fertilization experiments.…”

Ovarian fluid impacts flagellar beating and biomechanical metrics of sperm between alternative reproductive tactics

“…In turn, ovarian fluid has been shown to directly impact the outcome of a fertilization event by modifying sperm performance, i.e. motility and velocity (Urbach et al, 2005;Rosengrave et al, 2009a;Diogo et al, 2010;Gasparini et al, 2012;Galvano et al, 2013;Alonzo et al, 2016). This is related to changes in viscosity (Turner and Montgomerie, 2002), pH (Wojtczak et al, 2007) and/or ionic composition of activation media (Rosengrave et al, 2009b).…”

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

“…Positive effects of ovarian fluid on sperm motility parameters have been documented in several species, from salmonids (Lahnsteiner 2002, Turner & Mont gomerie 2002, Rosengrave et al 2009a, Kanuga et al 2012 to Gasterosteus aculeatus (Elofsson et al 2006) and Solea senegalensis (Diogo et al 2010). Although the intensity of these effects varies, from improving sperm velocity and longevity in Salvelinus alpinus (Turner & Montgomerie 2002) to being an essential factor in motility activation in Clupea pallasi (Cherr et al 2008), potential negative effects are normally only seen at very high concentrations of ovarian fluid which arrest the osmotic mechanisms needed for sperm motility activation (e.g.…”