Abstract
Motility and the expression of fertilizing ability by cauda epididymal rat spermatozoa, incubated in a chemically defined medium, were demonstrated to differ in their dependence on Ca2+ ions. Motility was optimal at 1.7 mM Ca2+, but fertilization rates were significantly at 2.6 and 3.4 mM Ca2+. Sperm motility apparently may not have to be maximized for fertilization to occur.