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

Spermatozoa of the sea urchin, Hemicentrotus pulcherrimus (10 cells/ml), preincubated with unfertilized eggs deprived of jelly coats (more than l0 cells/ml) at 20°C for 20min in Mg free artificial sea water containing 1 mM Ca (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 10 cells/ml in MFASW and of about l0 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.