Freezing Epididymal Spermatozoa of the Japanese Serow (Capricornis crispus) in Liquid Nitrogen

抄録

We examined the motility and sperm viability of frozen/thawed epididymal spermatozoa in the Japanese serow (Capricornis crispus) in order to develop a method for cryopreservation of genetic resources in this species. Thirty-four males captured in February and March of 1998 and 1999 were used. Epididymides were transported to the laboratory at 15 C and dissected in the medium I which contained egg-yolk (23.0%) and lactose (8.0%) and was buffered with 10% Tris solution (pH 7.4). Semen with sperm motility of more than 50% was used for the experiments. The semen was cooled to 5 C and diluted with freezing medium II which was freezing medium I supplemented with Equex Stem (1.4%) and glycerol (7.0 or 14.0%). The semen mixed with medium II was loaded into 0.25-ml plastic straws, and exposed to liquid nitrogen vapor for 10 min. The straws were then plunged into liquid nitrogen. Straws were thawed in a water bath kept at 37 C. Thawed spermatozoa were treated with a combination of fluorescent dyes, SYBR-14 and propidium iodide, to assess the sperm viability. The post-thaw motility of spermatozoa frozen with 3.5% and 7.0% glycerol were 10.0% and 11.2%, respectively; the proportions of living spermatozoa frozen with 3.5% and 7.0% glycerol were 6.9% and 6.1%. These results demonstrated that epididymal spermatozoa of the Japanese serow can be frozen in freezing medium containing glycerol, Equex Stem and egg-yolk.