Paddlefish (Polyodon spathula) spermatozoa: Effects of potassium and pH on motility

Direct observation of undiluted sperm of paddlefish (Polyodon spathula Walbaum, 1792) by dark field microscopy showed that most spermatozoa in the seminal plasma were immotile, with a few spermatozoa motile for up to 20 seconds. Spermatozoa were motile in solutions containing 0 to 0.5 mM KCl or KCOOH. Significant percentage of immotile spermatozoa were observed at 4 mM KCI and/or KCOOH solution of pH 6 and pH 9. The best motility (up to 100%) was observed after 10 seconds in TRIS-HCl buffered at pH 7 containing 1 mM KCI and in TRIS-HCl buffered at pH 8 and 7 containing 1mM KCOOH. Significantly, the best solution for short-term storage of sperm was that composed of 5 mM KCl with 20 mM TRIS-HCl pH 7. ANOVA test showed a significant influence of pH (p < 0.0001), (p < 0.0001) and KCl (p < 0.001), (p < 0.05) on the percentage of motility, after 1 and 16 hours of storage at 24 degrees C, respectively. This solution also regenerated the sperm ability to move from zero to 83 % motility after two hours storage, especially in sperm with pH lower than 7, contaminated with urine during collection of sperm and showing zero initial motility. No cummulative effect between 1 mM KCI and 5 mM CaCl2 as well as between 1 mM KCI and 100 mM glucose was observed on storage time of spermatozoa.