Induction of the Acrosome Reaction of Sea Urchin Spermatozoa by Means of Urea. (acrosome reaction/spermatozoa/urea/sea urchin)

Abstract

Urea is an effective reagent for inducing the acrosome reaction of spermatozoa in sea urchins [Hemicentrotus pulcherrimus, was used as material in most of the experiments. The following were used in some experiments: Pseudocentrotus depressus, Anthocidaris crassispina, Echinometra mathaei, Echinostrephus aciculatus, Toxopneustes pileolus, Tripneustes gratilla, Mespilia globulus and Glyptocidaris crenularis.] Urea-treated spermatozoa are capable of fertilizing eggs in Ca-deficient sea water. The pH of the urea solution is an important factor affecting the induction of the acrosome reaction. The reaction occurs at a high percentage in urea solution at pH higher than 7.8, while the reaction is almost completely suppressed at pH 7.2. Ca++ is also an important factor for the induction of the reaction, although the minimum concentration required is very low. The acrosomal filament formed in urea solution is similar in shape to that formed in egg-water, when fixed after a 10 s urea-treatment. The acrosome granule material is found around the basal portion of the acrosomal filament.