Sperm cryopreservation throughout the spawning season in Prochilodus lineatus

Abstract

The aim of this study was to determine the quality of Prochilodus lineatus sperm cryopreserved

throughout the reproductive season (November to March). Males (n=43) were monthly hand- stripped after carp pituitary treatment. Fresh sperm was subjectively analyzed for its motility

rate, motility quality score, duration of motility and morphology. Sperm was cryopreserved on 0.5 mL straws (n=258) using methyl glycol as cryoprotectant and glucose solution as extender. Post-thaw sperm was analyzed for its motility rate, velocities (curvilinear – VCL; straight-line – VSL; average path – VAP), and beat cross frequency (BCF) using a Computer-Assisted Sperm Analyzer (CASA). Frozen sperm morphology, oxidative stress (lipid peroxidation – LPO; reactive oxygen species – ROS; superoxide dismutase – SOD; catalase – CAT), and fertilization capacity (fertilization and hatching rates) were also evaluated. Seminal plasma was analyzed for pH, osmolality and ion concentration (Na+ , K+ , Ca2+ and Mg2+). P. lineatus fresh sperm presented good quality during the reproductive season, exhibiting motility rates above 80%, and post-thaw sperm quality was affected throughout the spawning season. Post-thaw sperm yielded higher (p<0.05) motility and VCL on December to March. Negative correlations were observed between sperm concentration and frozen sperm motility, sperm concentration and VCL, and Ca2+ concentration on seminal plasma and frozen sperm motility (p<0.01). Sperm concentration was positively correlated with Ca2+ concentration, CAT and ROS (p<0.01). CAT and fertility correlated positively (p<0.05). Increased CAT was efficient in reducing ROS and LPO in samples frozen in November, and maintained sperm fertilization capacity, although ROS activity affected sperm motility and VCL. Climate factors registered before the reproductive season also affected the quality of samples frozen at the beginning of the season. Although both fresh and post-thaw semen presented lower percentages of normal sperm cells on March, samples yielded good quality parameters such as motility rate, motility quality score, and VCL on this month. P. lineatus sperm cryopreserved from December to March exhibits better characteristics to undergo the stress induced by cryopreservation.