Cryopreservation of Sakhalin Taimen Hucho perryi Spermatozoa: Effect of Cryoprotectants on Post-thaw Fertility

Abstract: To develop the cryopreservation diluent for spermatozoa of the endangered Sakhalin taimen, we examined the effect of the nature of cryoprotectants on post-thaw fertility. Fresh semen was diluted 4 times with each diluent, comprising 90 % 300 mM glucose and 10 % each cryoprotectant (dimethyl sulfoxide (DMSO), methanol, or glycerol). The 100,ul of diluted semen was dropped on dry ice to freeze and immersed in liquid nitrogen for over 2 h. Four pellets were thawed in 16 ml of a 120 mM NaHC03 solution at 30t. Egg batches of 20 g were immediately inseminated with thawed semen (Sperm to egg ratio was 5.0 x 106: 1). Semen cryopreserved with methanol showed the highest fertilization rate (82.0 ± 0.9%) among all the cryoprotectants examined. The fertilization rate of semen diluted with DMSO (45.1 ± 2.2%) was significantly higher than that with glycerol (12.7 ± 2.0%). Semen cryopreserved with methanol yielded almost similar. post-thaw fertility to that of 50,u I of fresh semen (78.4 ± 2.4%) at the sperm to egg ratio of 2.5 x 106: 1. These results indicate that methanol is the suitable cryoprotectant for Sakhalin taimen spermatozoa