Change in the Respiratory Rate of Sea Urchin Spermatozoa following Sperm-egg Interaction in the Absence of Mg2+ : (sea urchin/sperm-egg interaction/Mg2+ free sea water/sperm respiration).

Abstract

Spermatozoa of the sea urchin, Hemicentrotus pulcherrimus (108 cells/ml), preincubated with unfertilized eggs deprived of jelly coats (more than l05 cells/ml) at 20°C for 20min in Mg2+ free artificial sea water containing 1 mM Ca2+ (MFASW), exhibited very low respiration, which was enhanced by 2, 4 dinitrophenol (DNP). The fertilization rate in MFASW was usually less than 5% and was about 25% at most. Preincubation with fertilized eggs (with and without a fertilization membrane) in MFASW did not reduced the respiratory rate of spermatozoa. The rate of sperm respiration was lower in MFASW than in artificial sea water (ASW), but was higher than the respiratory rate of spermatozoa preincubated in MFASW with unfertilized eggs. Sperm respiration in MFASW or in ASW was not stimulated by 2, 4 dinitrophenol. Almost complete inhibition of sperm respiration was obtained with unfertilized eggs fixed with glutaraldehyde at concentrations of above 105 cells/ml in MFASW and of about l04 cells/ml in ASW. The respiratory rate of spermatozoa treated with fixed eggs was enhanced by DNP. It is concluded that the respiratory rate of the spermatozoa is reduced by their interaction with unfertilized eggs before their penetration into the eggs.