Cryopreservation of sperm in common carp Cyprinus carpio: Sperm motility and hatching success of embryos

In this study, fish sperm cryopreservation methods were elaborated upon for ex situ conservation of nine strains of Bohemian common carp. Common carp sperm were diluted in Kurokura medium and chilled to 4 degreesC and dimethy l sulfoxide was added. Cryotubes of sperm with media were then cooled from +4 to -9 degreesC at a rate of 4 degreesC min(-1) and then from -9 to -80 d egreesC at a rate of 11 degreesC min(-1), held for 6 min at -80 degreesC, a nd finally transferred into liquid N-2. The spermatozoa were thawed in a wa ter bath at 35 degreesC for 110 s and checked for Fertilization yield, hatc hing yield of embryos, and larval malformations. Fresh and frozen/thawed sp erm were evaluated for the percentage and for the velocity of motile sperm from video frames using image analysis. The percentage and velocity of sper m motility at 15 s after activation of frozen/thawed sperm was significantl y lower than that of fresh sperm (nine males). ANOVA showed a significant i nfluence of fresh vs frozen/thawed sperm on fertilization rate (P < 0.0001) , but differences in hatching rate and in larval malformation (0-6.8%) were not significant, and different males had a significant influence on fertil ization and hatching rate (P < 0.003 and P < 0.007, respectively), Multiple range analysis (LSD) showed significant differences between fresh and froz en/thawed sperm regarding fertilization rate (68 +/- 11 and 56 +/- 10% resp ectively) and insignificant differences between fresh and frozen/thawed spe rm on the hatching rate (50 +/- 18 and 52 +/- 9%, respectively). The percen tage and velocity of fresh sperm motility were correlated, respectively, wi th the fertilization yield of frozen/thawed sperm at the levels r = 0.51 an d r = 0.54. (C) 2001 Academic Press.