Effect of pH, osmolality, Na⁺ and K⁺ on spermatozoa motility of the orange-spotted grouper, Epinephelus coioides

The present study investigated the biosensitivity of Epinephelus coioides spermatozoa under various ionic and osmolality conditions. Activation and sensitivity of sperm started at different pH (7, 7.5, 8, 8.5, and 9) level. The highest motility duration was obtained in pH 8.5 with a significant difference to other groups (P < .001). The E. coioides spermatozoa exposed to 600 mM NaCl solution, 300 mM KCl (in the medium containing 200 mM sucrose), and sucrose solutions with 1100 mosmol/kg osmolality had significantly higher duration of motility than those exposed to solutions with the lower amount of NaCl, KCl and osmolality. Any amount greater than 600 mM NaCl, 300 mM KCl and 1100 mosmol/kg osmolality showed a remarkable reduction in the motility of spermatozoa. Results also showed that the amount of 100 and 450 mM K+, and osmolality lower than 400 mosmol/kg had a significant inhibitory effect and prevented the activity of spermatozoa. The findings of this study showed that changes in K+, Na+ and osmolality of the external solutions affects the spermatozoa and its motility. The potential use of these ions could be applicable for the improvement of the spermatozoa quality of E. coioides during artificial reproduction.