Inhibitory effect of K^+ and Ca^{2+} concentrations, pH, and osmolality of activation solution on motility of shabut (Barbus grypus Heckel 1843) spermatozoa


Abstract: Evaluation of sperm quality is important in order to understand the main biochemical processes occurring during motility of sperm, to determine the reproductive ability of fish species, and to optimize the environment for spermatozoa. Generally, once differentiated in the gonad the sperm remain there completely quiescent until they are released into an external medium. After activation, motility duration of fish spermatozoa is greatly affected by environmental factors such as pH, ion concentrations, and osmotic pressure. Investigating these factors in relation to fish sperm can help establish good activation or immobilizing media for improving artificial fertilization and preservation. This study aimed to determine the effect of activation solution pH, ions (K^+ and Ca^{2+}), and osmolality on the motility of cultured shabut (Barbus grypus Heckel 1843) sperm. The best pH level for activation of spermatozoa was pH 9.0. Ionic factors can stimulate the initiation of sperm activation and duration. Maximum percentage and duration of motile sperm were observed in solutions containing 5 mM K^+ and no Ca^{2+} with an osmolality of 56 mOsmol kg^{–1}. Concentrations of more than 20 mM K^+ and more than 10 mM Ca^{2+} had negative effects on sperm motility.

Keywords: Barbus grypus, activation solution, sperm motility, K^+, Ca^{2+}, pH, osmolality

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