Qualidade do sêmen e sua congelabilidade ao longo da estação reprodutiva em Prochilodus lineatus e Brycon orbignyanus

Abstract

The aim of this study was to determine fresh and frozen sperm quality over two spawning seasons (2013-2014; 2014-2015) in Prochiloduslineatus and Bryconorbignyanus. The spawning seasons were divided into two periods: November to December and January to February. Males were hand-stripped after carp pituitary treatment.Fresh sperm motility rate, velocities (curvilinear = VCL; straight-line = VSL; average path = VAP), and beat cross frequency (BCF) were determined using a Computer-Assisted Sperm Analyzer (CASA). Sperm of each species was frozen using methyl glycol as cryoprotectant and a glucose solution for P. lineatus and a NaCl solution for B. orbignyanuswere used as extenders. Diluted sperm was loaded into 0.25 mL straws, then frozen in a nitrogen vapor vessel (dry shipper) and stored in a liquid nitrogen vessel. Six months later, straws were thawed in a water bath at 60°C for 3 s and sperm quality was determined, as described for fresh sperm. No significant difference was observed for any of the fresh and frozen sperm features between or over the two spawning seasons forP. lineatus and B. orbignyanus. Motility rate and velocities, but not BCF, were always higher in fresh sperm when compared with frozen sperm. Comparing both species, higher motility in frozen sperm and higher VCL and VAP in both fresh and frozen sperm were observed in P. lineatus, while higher VSL in fresh sperm and higher BCF in fresh and frozen sperm were observed in B. orbignyanus. Sperm quality and its freezing ability remained over the spawning season for both species and thus fish farmers can reproduce these species and freeze their sperm at any time throughout the spawning season. P. lineatussperm is more resistant to the cryopreservation process than B. orbignyanus.