. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 282 H. SCHUEL ACTIVATION POTENTIAL OF EGG IN 10"'M Cq'^-SW AND IN SW +23 mV +24 mV 10~''M Ca^*-SW. Figure 6. Recording of fertilization potential of egg inseminated in sea water containing mM Ca^^ ( ), compared with egg fertilized in normal (10 mM Ca*^) sea water ( ). to polyspermy. This expectation has been realized since such eggs are highly vulnerable to polyspermy (Jaffe, 1976; DeFelice and Dale, 1979; Whitaker and Steinhardt, 1983). (2) Eggs fertilized in low sodium sea water, which suppresses the fertilization
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 282 H. SCHUEL ACTIVATION POTENTIAL OF EGG IN 10"'M Cq'^-SW AND IN SW +23 mV +24 mV 10~''M Ca^*-SW. Figure 6. Recording of fertilization potential of egg inseminated in sea water containing mM Ca^^ ( ), compared with egg fertilized in normal (10 mM Ca*^) sea water ( ). to polyspermy. This expectation has been realized since such eggs are highly vulnerable to polyspermy (Jaffe, 1976; DeFelice and Dale, 1979; Whitaker and Steinhardt, 1983). (2) Eggs fertilized in low sodium sea water, which suppresses the fertilization potential (Fig. 5), should be highly susceptible to polyspermy. This expectation has been realized since polyspermy results when eggs are fertilized in sodium depleted (choline-substituted) sea water (Nishioka and Cross, 1978; Jaffe, 1980; Schuel and Schuel, 1981). However, ahhough a high incidence of polyspermy is obtained, the eggs do not fill up with supernumerary sperm when heavily inseminated in low sodium sea water (Schuel and Schuel, 1981). Two factors tend to limit sperm pen- etration under these conditions: the normal completion of the cortical reaction (Schuel and Schuel, 1981), and the adverse effects of the low sodium environment on sperm fertility (Schuel and Schuel, 1981; Bibring et al, 1984). (3) Eggs fertilized in calcium-depleted sea water, which suppresses the first com- ponent (segment a) of the fertilization potential (Fig. 6), should be susceptible to polyspermy. Such a phenomenon might account, in part, for the elevated polyspermy seen in 80% isotonic magnesium chloride/20% sea water (Clark, 1936). Magnesium is a potent ionic antagonist of calcium (Heilbrunn, 1956), and could suppress the calcium component of the fertilization potential (Jaffe, 1980). Increased polyspermy was not observed when eggs were fertilized with acrosome reacted sperm in zero calcium sea water (Schmidt et al., 1982). However, sperm fertility is reduced 20X in zero calcium sea water
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