title: Sperm dilution ratio affects post-thaw motility rate and velocity of Prochilodus lineatus (Characiformes) sperm.
abstract: There is a lack of standardization in sperm cryopreservation of aquatic organisms and, thus, a necessity of more accurate investigations in all steps of this process. In this study, the effects of sperm dilution ratio on post-thaw sperm quality of Prochilodus lineatus were evaluated. Sperm was diluted in a standard freezing medium (glucose and methyl glycol) at four different ratios (sperm to final volume = 1:5, 1:10, 1:50 or 1:100), frozen in a nitrogen vapour vessel at -170°C and then stored in liquid nitrogen vessel at -196°C. Post-thaw motility rate and velocities (curvilinear = VCL; average path = VAP; straight line = VSL) were determined using a Computer-Assisted Sperm Analyzer (CASA) at 10 and 40 s post-activation. The highest motility rates were observed when sperm was frozen at a ratio of 1:5 (76%) and 1:10 (75%). The highest VCL (225 μm/s) and VAP (203 μm/s) were observed at a ratio of 1:10, while VSL was similar among samples frozen at 1:5, 1:10 and 1:50 (97-124 μm/s). When those parameters were evaluated again 30 s later, motility decreased significantly in samples frozen at a ratio of 1:5 (57%) and 1:10 (61%), while velocities decreased significantly in all samples regardless of dilution ratio (75-85 μm/s of VCL, 38-53 μm/s of VAP and 25-39 μm/s of VSL). P. lineatus sperm should be frozen at a ratio of 1:10, where both the number of loaded sperm per straw and the post-thaw quality are maximized.
authors.affiliation: Animal Science Department,Federal University of Lavras,P.O. Box 3037,Lavras,MG,37200-000,Brazil.
authors.forename: Ana T M
authors.initials: AT
authors.lastname: Viveiros
authors.affiliation: Department of Animal Science,Federal University of Lavras,Minas Gerais,Brazil.
authors.forename: Marcelo C
authors.initials: MC
authors.lastname: Leal
mesh_terms: D000818:Animals; D060125:Characiformes / Q000502:physiology; D015925:Cryopreservation / Q000379:methods*; D003470:Culture Media / Q000737:chemistry; D008297:Male; D012662:Semen Preservation / Q000379:methods*; D013081:Sperm Motility; D013094:Spermatozoa / Q000502:physiology*
chemical_list: D003470:Culture Media
keywords: CASA; Cryopreservation; Fish; Neotropical; Semen