Effectiveness of glucose–methanol extender for cryopreservation of Huso huso spermatozoa

•Glucose concentration is important for the cryopreservation of beluga sturgeon sperm.•Sperm of beluga sturgeon was effectively cryopreserved with glucose–methanol.•The optimal cryopreservation conditions were found to be 0.2M glucose in the extender. The present approach was designed to evaluate the methanol–glucose extender effects on sperm cryopreservation in beluga sturgeon, Huso huso. Sperm quality was examined by measuring post-thaw sperm motility and fertilizing rate at hatching stage. We first tested the effect of glucose concentration (0, 0.10, 0.15, 0.20 and 0.30M) in a methanol extender on post-thaw sperm motility. The optimal cryopreservation conditions were found to be 0.2M glucose in the extender. Then, motility and fertilization rates of sperm cryopreserved with 0.2M glucose and 10% methanol (GM) were compared to Tris–sucrose–KCl in 10% methanol extender (TSKM). Additionally, sperm motility and fertilizing ability in relation to 15 and 30min equilibration in GM extender before and after cryopreservation were measured. Higher post-thaw sperm motility duration and percentage as well as fertilization rate were obtained with the GM extender when compared to TSKM extender. Equilibration of sperm in extender did not affect the motility quality of either fresh-diluted or frozen/thawed sperm, while fertilization rate showed a significant decline alone after 30min of post-thaw storage. Our results indicated that the use of a simple extender consisting of 0.2M glucose in 10% methanol can be an alternative cryopreservation method to those previously described for sturgeons.