Optimisation of sodium and potassium concentrations and pH in the artificial seminal plasma of common carp Cyprinus carpio L

Abstract

The effect of sodium and potassium concentrations as well as optimal pH on the motility of common carp Cyprinus carpio L. sperm during short-term storage in artificial seminal plasma (ASP) was investigated. Sperm was collected from individual males (n = 5) and each sample diluted tenfold (1:9) in ASP (sperm:extender) containing 2 mM CaCl₂, 1 mM Mg₂SO₄ and 20 mM Tris at pH 8.0 and supplemented by the following concentrations of sodium and potassium (mM/mM): 0/150, 20/130, 40/110, 75/75, 110/40, 130/20 and 150/0. The osmolality of all ASP variants was set at 310 mOsm kg^-1. Sperm motility was measured using a CASA system during 72 h of storage. Immediately after dilution, sperm motility was high (90%) both in each variant and in the control group (fresh sperm). After 72-h storage, the highest sperm motility was noted in ASP containing 110 mM NaCl and 40 mM KCl. No differences were found in the motility of samples preserved within the pH range of 7.0-9.0. Our data suggest that for the short-term storage of common carp sperm, whereas the pH of the solution does not play a crucial role, a specific potassium concentration of around 40 mM is required.

Keywords: Artificial seminal plasma; Chilled storage; Common carp; Potassium; Sodium; Sperm preservation; pH.

Fig. 1

Effect of different dilution ratio (mean ± SD), i.e. × 2 (1:1), × 5 (1:4), × 10 (1:9), × 20 (1:19) and × 40 (1:39), on sperm motility (MOT, %) of common carp Cyprinus carpio L. during 72 h of short-term storage in ASP (75 mM NaCl, 70 mM KCl, 2 mM CaCl₂, 1 mM Mg₂SO₄, 20 mM Tris at pH 8.0). Undiluted sperm was used as a control. Different superscripts, i.e. a, b, and c, indicate statistical differences between time points for the same dilution ratio whereas different superscripts, i.e. x, y, and z, indicate statistical differences between the dilution ratio at the same time point (P < 0.05)