Abstract：Taimen (Hucho taimen) is a rare cold-water fish that mainly distributes in the Irtysh River and Heilongjiang River. Studies on the cryopreservation of H. taimen sperm and establishment of cryobank are of great values in many aspects, such as the preservation of resources, artificial reproduction and breeding of fish, rearing of the larval, and also the recovery of the population. In the present study, 9 types of sperm diluents (MPRS, RS, Hanks, ELS, EG1, EG2, Stein, SS-2 and D15) that consisted of the basic liquid medium plus inorganic salt, glucose, and fetal bovine serum (FBS) were prepared and used for the cryopreservation of H. taimen spermatozoa. The motility of spermatozoa, in these diluents with or without the cryoprotectant ((dimethyl sulfoxide, DMSO) or MeOH), and also after the freezing treatment with liquid nitrogen, was detected. The results showed that the sperm motility was relatively high (73.00±2.65)%~(96.67±2.08)% in each diluents mentioned above, however declined after the addition of the DMSO, and only possessed a quite low activity (1.21±0.00)% or (1.1±0.00)% with ELS or D15 after the freezing treatment. Furtherly, a suitable concentration of MeOH or DMSO was screened out with ELS and the results were as follows. It was found that the sperm motility remained at (79.00±6.52)%~(88.80±7.89)% after a 20 min pre-freezing treatment with MeOH at the concentrations of 4%~12%. The sperm motility was significantly (P＜0.05) decreased after the freezing treatment compared with the fresh semen, and a relatively high ratio had been to (18.33±10.61)% with 6% of MeOH. On the other hand, the motility of the perm had ranged of (43.75±11.09)% ~(81.67±2.89)% after the pre-freezing treatment with DMSO (4%~12%) for 5 min, and was tremendously declined (3.25±0.30)%~(45.00±5.77)% after the treatment for 20 min, but still kept a rather low activity (1.00±0.00)%~(2.75±1.50)%(P＜0.05) after the freezing treatments. D15 was used as the basic diluents to screen out the concentrations of glucose. The results showed that the sperm motility was relatively high (17.80±2.59)% after the freezing treatment with glucose at the concentration of 30% (D30), but still was significantly (P＜0.05) lower than the fresh semen. In addition, a short-term preservation results conducted with 4 diluents (D15, D30, Stein and ELS) indicated that the sperm had the longest survival time (45 h) with Stein diluents, moderate with D30 (15 h). In conclusion, the H. taimen sperm cryopreserved with ELS and D30 plus with 6% MeOH had a certain degree of motility. Our results will lay the foundations for the cryopreservation of H. taimen sperm on a large scale and furtherly provide the basis for the establishment of the sperm cryobanks.
