Sperm motility evaluation following long-term storage (5 years) of cryopreserved sea bream (Sparus aurata L., 1758) semen

Abstract

The aim of this study was to evaluate, by computer-assisted analysis, the motility parameters of cryopreserved sea bream spermatozoa after prolonged storage (up to 5 years) in liquid nitrogen in comparison to the performances of fresh semen and of semen thawed 1 month after freezing (cryopreservation medium: 1% NaCl containing 5% DMSO; freezing rate: 10°C min-1; stored in liquid nitrogen). Semen samples were thawed 1 month and 5 years after cryopreservation. Sperm motility was analyzed by means of the Sperm Class Analyzer® (SCA, Microptic, Barcelona, Spain). The percentages of motile sperm and rapid sperm curvilinear velocity >100 μm s-1 only), and the curvilinear, straight-line and average path velocities (μm s-1) were evaluated. The percentages of total motile and rapid sperm, as well the relative velocity levels, were slightly lower in thawed semen than in fresh semen (for example, 85 vs 95% for total motile sperm; 70 vs 80% for rapid sperm; 200 vs 300 μm s-1 for VCLt; 250 vs 350 μm s-1 for VCLr). Data of all trials did not differ in relation to storage time. It can therefore be concluded that long-term storage of large amounts of cryopreserved semen was homogeneous, providing high quality sea bream semen for use in fertilization trials in both aquaculture and laboratory research.