. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 92 J. W. LYNN ET AL $a%, j£p;;3V- .»•• »-r A*Hr>* -j ""*•• V*cv/ J^ .-y^^te^^^l., .. Figures 20-23. A series of TEM micrographs of Sicyonui in.vciili^ eggs spawned into ASW or ChCl- substituted seawater, treated at either 4 or 15 min post HE elevation with I M urea for 5 min, washed and prepared for EM. Arrowheads = HE: PVS = perivitellme space; Bar = 0.5 fjm for all. Figure 20. ASW at 4 mm. Dense outer layer remains, but inner flocculent layer is absent (compare to Fig. 13). Figure 21. ChCI-substituted seawate

- Image ID: RHMXRA
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 92 J. W. LYNN ET AL $a%, j£p;;3V- .»•• »-r A*Hr>* -j ""*•• V*cv/ J^ .-y^^te^^^l., .. Figures 20-23. A series of TEM micrographs of Sicyonui in.vciili^ eggs spawned into ASW or ChCl- substituted seawater, treated at either 4 or 15 min post HE elevation with I M urea for 5 min, washed and prepared for EM. Arrowheads = HE: PVS = perivitellme space; Bar = 0.5 fjm for all. Figure 20. ASW at 4 mm. Dense outer layer remains, but inner flocculent layer is absent (compare to Fig. 13). Figure 21. ChCI-substituted seawate
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Image ID: RHMXRA
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 92 J. W. LYNN ET AL $a%, j£p;;3V- .»•• »-r ~A*Hr>* -j ""*•• V*cv/ J^ .-y^^te^^^l., .. Figures 20-23. A series of TEM micrographs of Sicyonui in.vciili^ eggs spawned into ASW or ChCl- substituted seawater, treated at either 4 or 15 min post HE elevation with I M urea for 5 min, washed and prepared for EM. Arrowheads = HE: PVS = perivitellme space; Bar = 0.5 fjm for all. Figure 20. ASW at 4 mm. Dense outer layer remains, but inner flocculent layer is absent (compare to Fig. 13). Figure 21. ChCI-substituted seawater at 4 min. The HE is fluffier than the dense outer layer remaining in Figure 20 and collapsed onto the egg surface. Figure 22. ASW at 15 mm. The HE retains the normal morphology of a dense outer stratum over an inner flocculent layer. Figure 23. ChCI-substituted seawater at 15 min. The HE remains Huffy and collapsed onto the egg surface. There is no distinct morphological difference between the ChCI-substituted. urea-treated HE at 4 nun and this later time point. shrimp egg. the envelope was not completely removed with urea in either normal or ChCI-substituted seawater. Therefore, the exocytosis of the dense granules combining with the pre-existing surface coat formed a very stable HE template ("thin HE" of Pillai and Clark, 1988) within 4 min of its appearance. This initial stage of HE formation, then, appears to be independent of the absence of sodium or the presence of choline. In contrast, the fertilization envelope of sea urchins remains labile to urea solubili- zation for up to 10 min in both normal and sodium-de- pleted seawatei idicating the time required for effective crosslinking (Schu. al, 1982). Second, HEs of shrimp eggs in normal seawater at 15 min were not affected by urea. Both the outer dense and inner flocculent layer appeared to be intact, implying that the insertion and crosslinking of ring vesicle material into the outer dense layer wa
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