The effects of nitrites (NO2-) and nitrates (NO3-) on sperm motility of common carp in vitro

Abstract

The effects of nitrogenous compounds on carp sperm were investigated. The freshly collected carp sperm was incubated for 2 hours at 4°C in the presence of different concentrations of nitrites (NO₂^-) and nitrates (NO₃^-). Sperm motility was determined with the use of computer assisted sperm analysis - CASA. The parameters of sperm movement assessed in the experiments were: VCL - curvilinear velocity (mm s^-1), VSL - straight line velocity (mm s^-1), VAP - average path velocity, (mm s^-1), MOT - percent of motile sperm.
Analysis of these parameters showed that nitrites (NO₂^-) did not significantly change VCL, VSL and VAP parameters at any of the tested concentrations. Significant differences (p<0.05) were only observed in the percent of motile sperm (MOT) after the incubation with nitrites at the concentration of 2000 mg N l^-1. Nitrates (NO₃^-) at the concentration of 2000 mg N l^-1 significantly diminished VCL, VSL, VAP and MOT parameters of sperm movement. We conclude that sperm movement can be negatively affected by relatively high concentrations of nitrites and nitrates, the latter being more harmful to motility. Additional studies are needed to clarify if the long term exposure of fish to nitrites and nitrates in lower concentrations will affect the sperm motility.