Calcium‐induced quiescence of sperm motility in the bluegill (Lepomis macrochirus)

Abstract

Before dilution in hypoosmotic media sperm of freshwater fish are maintained quiescent by a range of factors including osmolality, K+ and pH, and the onset of motility is generally associated with an increase in cytoplasmic Ca2+. In contrast, Ca2+ in conjunction with osmolality was found to inhibit motility of intact bluegill sperm. Consistent with seminal plasma composition, 0.16 mmol/L Ca2+ and greater, in conjunction with an osmotic concentration of 290 mOsm/kg, inhibited the onset of bluegill sperm motility; sperm diluted in saline at 290 mOsm/kg without Ca2+ became motile. Cations Mn2+ and Sr2+, in conjunction with osmolality, had an inhibitory effect on initiation of sperm motility similar to that of Ca2+. Sperm motility was inhibited by Ca2+ channel blockers nimodipine and nifedipine, the mitochondrial Ca2+ uniporter inhibitor ruthenium red and the calmodulin inhibitors W-7 and trifluoperazine dihydrochloride. These results provide evidence that elevated cytoplasmic Ca2+ inhibits sperm motility and yet low levels permit or promote motility. This study demonstrates a unique inhibitory action of Ca2+ on the motility of intact fish sperm at physiologically relevant levels.

Influence of the ionic and protein environment on sperm motility activation in the European eel

“…In some marine species inhibitors of voltage-gated calcium channels reduced or suppressed sperm motility (Atlantic croaker Micropogonias undulatus, Detweiler and Thomas 1998;Pacific herring, Clupea pallasi, Vines et al, 2002). In addition, inhibitors of voltage-gated calcium channels inhibited sperm motility in other freshwater species, including the bluegill (Lepomis macrochirus; Zuccarelli and Ingermann, 2007) and sterlet (Acipenser ruthenus; Alavi et al, 2011), and reduced sperm curvilinear velocity (VCL) in redside dace (Clinostomus elongatus; Butts et al, 2013).…”