. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLYSPERMY BLOCKS 283 granule secretion mediated block can be suppressed by soybean trypsin inhibitor (Schuel and Schuel, 1981). The rationale for these experiments was based on previous observations that a soybean trypsin inhibitor (SBTl) sensitive protease is secreted by the egg's cortical granules at fertilization (Schuel et al, 1973; Vacquier et ai, 1973), that SBTI inhibits the cortical reaction and promotes polyspermy (Hagstrom, 1956a; Lonning, 1967; Longo and Schuel, 1973), that SBTl-treated eggs are monospermic initi
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLYSPERMY BLOCKS 283 granule secretion mediated block can be suppressed by soybean trypsin inhibitor (Schuel and Schuel, 1981). The rationale for these experiments was based on previous observations that a soybean trypsin inhibitor (SBTl) sensitive protease is secreted by the egg's cortical granules at fertilization (Schuel et al, 1973; Vacquier et ai, 1973), that SBTI inhibits the cortical reaction and promotes polyspermy (Hagstrom, 1956a; Lonning, 1967; Longo and Schuel, 1973), that SBTl-treated eggs are monospermic initially and gradually become polyspeimic with time (Hagstrom, 1956a; Longo and Schuel, 1973; Longo et ai, 1974; Schuel et ai, 1976a), and that all potential sperm penetration sites remain available at the surface of SBTI-treated Arhacia eggs for 3 min post insemination (Schuel et ai, 1976a; also see Cortical granule protease section, below). Under these conditions the time at which the SBTl-treated eggs first became polyspermic (Schuel and Schuel, 1981) was used to titrate the decay of the rapid block (Fig. 7). The half time for the first supernumerary sperm fusion event in natural (425 mM Na^) sea water is ± s, compared to ± s in 26 mM Na^ {P < ). Furthermore, the decay in the rapid block corresponded to the period iOOr o o c o o *^ Q. ^ O • SBTI in SW (425mMNaM o SBTI in SW (26 mM No") 120 180 Time (sec) 300 Figure 7. Kinetics of sodium-dependent block to polyspermy in Arhacia punctulata eggs as determined by the rate at which eggs become polyspermic in ml SBTI ( mg/ml) dissolved in natural (425 mM Na"^) and choline-substituted (26 mM Na"^) sea water. Eggs inseminated with excess ( ml of 8%) sperm. Unfused sperm were killed at indicated times by addition of equal volume of sodium laur\l sulfonate (Hagstrom and Hagstrom, 1954), final concentration Incidence of polyspermy estimated by counting multipolar divisions
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