Post-thaw dilution of Rhamdia quelen sperm improves the reproductive success

The aim was to evaluate the effect of a post-thaw dilution of Rhamdia quelen sperm in 1.1% NaCl (325 mOsm kg(-1); pH 7.6; 24 degrees C) solution on the quality and reproductive capacity. Sperm from eight males were cryopreservation in nitrogen vapor at -170 degrees C for 18 h in 0.25 mL straws in a freezing medium containing 5% fructose, 5% Powdered milk, and 10% methanol. The samples were thawed and post-thaw diluted (1:20) in NaCl solution or not (control). The higher spermatozoa velocities were observed in the post-thaw diluted samples (curvilinear (VCL) -69 +/- 11 pm s(-1); average path (VAP) -45 +/- 8 pm s(-1); straight-line (VSL) -43 +/- 8 pm s(-1)) compared to the control (VCL -47 +/- 10 pm s(-1); VAP -31 +/- 6 pm s(-1); VSL -30 +/- 6 pm s(-1)). Greater straightness (STR), progression (PROG), and beat cross frequency (BCF) were observed in the post-thaw diluted samples (STR -96 +/- 7%; PROG -666 +/- 128 pm; BCF -42 +/- 2 Hz) than in control (STR -95 +/- 5%; PROG -463 +/- 92 pm; BCF -40 +/- 2 Hz). The strongly curled tail was the only morphology change that differ between the post-thaw diluted (5 +/- 2%) and control (2 +/- 1%). Membrane integrity, mitochondrial activity, and normal larvae rate were not different between treatments. Fertilization and hatching were higher in the post-thaw diluted sperm (93 +/- 3%; 82 +/- 9%) when compared to control samples (65 +/- 13%; 55 +/- 17%). Were used oocytes from one female, limiting these results. The post-thaw dilution improved the sperm kinetics and reproductive parameters. Thus, this methodology can be included in the sperm cryopreservation protocol for R. quelen.