The Effects of Osmolality, Cryoprotectant and Equilibration Time on Striped Bass Morone saxatilis Sperm Motility

Abstract Four experiments were designed to evaluate the effects of osmolality, cryoprotectant, and equilibration time on striped bass sperm motility. In the first experiment, solutions of NaCI or KCI with osmolalities ranging from 0 to 700 mmol/kg were tested on sperm activation. Over 60% of the sperm were activated by isotonic NaCI and KCI solutions with a treatment osmolality of 350 mmol/kg. Sperm remained motile until osmolality increased to 600 mmol/ kg. In the second and third experiments, Extenders 1, 2 and 3 with osmolalities of 350, 500, and 600 mmol/kg, respectively, were tested. Sperm samples stored in Extender 2 showed significantly higher ( P 0.01) sperm motility after 10 min of exposure as well as greater ( P < 0.01) post‐thaw motility when compared to samples stored in Extenders 1 and 3. In the fourth experiment, two trials were carried out to evaluate the effects of cryoprotectant and equilibration time. In the first trial, methanol with a concentration of 5% and 10% yielded the highest ( P < 0.05) sperm motility prior to freezing at all equilibration times examined. However, 5% DMSO yielded the highest ( P < 0.01) post‐thaw motility (38 ± 3.6%). DMSO with concentrations of 10% and 15% resulted in 17 ± 2.3% and 6 ± 1.0% post‐thaw motility, respectively. Both methanol and DMA, at all concentrations tested, resulted in less than 10% post‐thaw motility. In the second trial, four DMSO concentrations with three different equilibration times were examined. We observed a significant ( P < 0.001) interaction effect between DMSO concentration and equilibration time. Post‐thaw motility was significantly greater ( P < 0.01) with a concentration of 5% DMSO at all equilibration times examined, compared to 1.25, 2.5, and 10% DMSO. An average post‐thaw motility of 40 ± 2.9% was achieved after 10 min equilibration using 5% DMSO.