Effects of Glycerol Concentration on Semen Cryopreservation in Blue Foxes and Ultrastructure of Sperma tozoa Subjected to the Process of Freezing-thawing

Eight high quality male blue foxes from Finland were chosen for semen collection by digital manipulation and diluted with the extender Ⅰ.The diluted sperm were divided into four fractions and the same volume of the extender Ⅱ containing glycerol was added to reach the final glycerol concentration of 2%,4%,6%,8% (v/v) ,respectively.After equilibrated for 2 h at 5 ℃.Semen samples were packed in 0.5 mL plastic straws and frozen on a rack 5 cm above liquid nitrogen and thawed at 70 ℃ for 9 s.Before and after freezing-thawing,not only the effects of different concentrations of glycerol on changes of spermatozoa characteristics but also the alterations of ultrastructure of spermatozoa by Transmission Electron Microscope were studied.The results showed,the motility and plasma membrane integrity of spermatozoa together with the percentage of intact acrosomes were related to the dose of glycerol.All these characteristics reached the highest in the fraction that the final glycerol concentration was 4% (41.8%,43.6%,48.4%) and the lowest appeared in the fraction of 2% (24.5%,27.6%,31.7%).Along with the extension of incubation,characteristics of spermatozoa in both fractions of 2% and 4% were significant differences while the differences between 2%,6% and 8% were insignificant.After 6 hours,the motility of each fraction was not more than 10% while the highest viability and the percentage of intact acrosomes were 11.8% and 12.7% respectively.The optimum concentration of glycerol was 4% in the extenders of freezing spermatozoa for blue fox.The living time of spermatozoa subjected to the process of freezing and thawing was short.The plasma membrane was expanded extremely or broken and the acrosome was vesiculated or dispersed while plasma membrane and acrosome seldom lost.