The effect of various DMSO concentrations on the mobility parameters of beluga sperm

The widespread use of dimethyl sulfoxide (DMSO) as a cryoprotector for fish spermatozoa, including relict sturgeons, as well as a solvent for lipophilic antioxidants introduced into basic DMSO-containing cryoprotective media, increases the risk of cryodamage to reproductive cells of these fish species, which have low cryoresistance. The work investigated the effect of different concentrations of this cryoprotector (10, 11, 16, 21, 27 and 32%) in the cryoprotective medium (3 mmol/l KCl, 111 mmol/l NaCl, 2 mmol/l CaCl2, 24 mmol/l NaHCO3 and 200 mmol/l glucose) on the parameters of beluga sperm motility (percentage of motile cells and cell movement time) before and after cryopreservation. With an increase in the concentration of DMSO, a significant decrease in the percentage of motile beluga spermatozoa was found after the equilibration stage for 15 min, which confirms the toxicity of this cryoprotector for sturgeon spermatozoa. Beluga sperm, defrosted after freezing and low-temperature (–196 °C) storage for 3 days, demonstrates only 10.5–2.8% of the motility before cryopreservation, with the exception of a DMSO concentration of 32%, at which motility is already 87.5% of the sperm motility before freezing. Non-monotonic dependencies of the motility of defrosted sperm, as well as the duration of sperm movement before and after cryopreservation on the DMSO concentration were established, which indicates the importance of optimizing the protocols for preserving the reproductive cells of male sturgeons using DMSO-containing cryoprotective media.