Inhibitory effect of sodium bicarbonate on the motility of sperm of Japanese eel

Abstract

Sperm motility of Japanese eel Anguilla japonica was depressed from 59.1 to 1.1% when NaHCO 3 concentration increased from 0 to 150 mM. In 25 mM NaHCO 3 , when pH of the medium was 6.2, 7.2, 8.2, 9.2 and 10.2, relative sperm motility was 0, 0, 55.8, 93.7 and 136.6%, respectively to that of the control (0 mM NaHCO 3 ). The remarkable effect in acid or neutral condition indicates that free‐CO 2 (liberated CO 2 and H 2 CO 3 ) is a key factor for the motility inhibiting effect of NaHCO 3 .