Sperm characteristics in Grass carp, Ctenopharyngodon idella; effect of ions on spermatozoa motility and fertilization capacity

In this study, sperm characteristics (motility parameters and ionic composition of seminal plasma) and effect of ions on motility (duration of motility of sperm and percentage of motile spermatozoa) and fertilization capacity (fertilization rate, hatching rate, survival rate and larvae length) were investigated in Ctenopharyngdon idella. The longest duration of motility obtained in solution containing 104 mM NaCl. The highest fertilization capacity was observed in solution containing 112 mML NaCl. Solutions containing different concentrations of KCl caused a decrease on the percentage of motile spermatozoa; fertilization rate and hatching rate, but duration of sperm motility and survival rate were significantly higher in solution containing 440 and 320 mM KCl, respectively. There was a decreasing trend on motility when spermatozoa incubated in solutions containing MgCl2 compared to the control. Similarly, higher motility parameters in terms of percentage of motile spermatozoa and duration of sperm motility were observed in distilled water. The sperm motility just after activation was suppressed by concentrations of CaCl2 of 32 mg/dL or more. The maximum hatching rate, survival rate and larvae length were observed in 32 mg/dL CaCl2. Understanding the effects of these ions is helpful to the aquaculture industry as it allows for the development of optimal artificial reproduction methods and contributes towards the knowledge base of better short-term fish semen preservation conditions.