Regulation of spermatozoa motility in response to cations in Russian sturgeon Acipenser gueldenstaedtii

The aim of this study was to investigate the response of Russian sturgeon (Acipenser gueldenstaedtii) sperm to external cations (Na+, K+, Ca2+, and Mg2+) and their susceptibility on the induction of motility and swimming behavior. An in vitro spermatozoa motility assay was used by a computer-aided Motion-Analysis system. Sperm motility was inhibited by 60 mm NaCl (∼140 mOsm/kg) and 0.7 mm KCl solutions (∼ 21.4 mOsm/kg). The Ca2+ and Mg2+ ions were not able to inhibit spermatozoa motility. By contrast, Na+ within a limited concentration range (between 45 and 55 mm) was able to reverse the inhibitory effect of K+ at the critical concentration (0.7 mm). Ca2+ and Mg2+ were also able to reverse the K+-mediated spermatozoa motility restriction at concentrations starting at 0.01 and 0.1 mm, respectively. These results provide evidence for the role of K+ in suppressing spermatozoa motility, and suggest that Ca2+, Mg2+, and possibly Na+ trigger motility in Russian sturgeon sperm.