. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 3. Fusion of partial pronuclei. Numerals are times in mm after fertilization. The two pronuclei fused at 17 min. Sperm aster is not clear in this series of pictures. The picture taken at 36 min shows the nuclear envelope starting to break down. At 42 min, polarization-optical observation reveals the anaphase spindle. 26°C. Scale bar = 25 >im. eggs activated by treatment with 10 Mg/ml Ca-ionophore (A 23187) for 2 min (Fig. 5), although the migration started later and was slower (Fig. 6) than that observed for normal
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. Figure 3. Fusion of partial pronuclei. Numerals are times in mm after fertilization. The two pronuclei fused at 17 min. Sperm aster is not clear in this series of pictures. The picture taken at 36 min shows the nuclear envelope starting to break down. At 42 min, polarization-optical observation reveals the anaphase spindle. 26°C. Scale bar = 25 >im. eggs activated by treatment with 10 Mg/ml Ca-ionophore (A 23187) for 2 min (Fig. 5), although the migration started later and was slower (Fig. 6) than that observed for normally fertilized eggs (also noticed by Mar, 1980). In any event, partial nuclei in activated eggs behaved sim- ilarly to single nuclei. Microtubule inhibitors suppress the migration of nuclei towards syngamy (Zimmerman and Zimmerman, 1967; Schatten and Schatten, 1981; Hamaguchi and Hiramoto 1986). Movement of Clypeaster nuclei was stopped by treating eggs with 1 mAl colchicine in seawater 5 min after activation. The movement of partial nuclei was sim- ilarly suppressed, and they remained separated, failing to form a single nucleus (Fig. 7). Yet both nuclei eventually exhibited the breakdown and reformation of their nuclear envelopes, as was observed in mononucleate eggs treated with either Colcemid (Sluder, 1979. 1986) or colchicine (Yoneda and Schroeder, 1984). In several aspects, therefore, the partial nuclei behave very similarly to single nuclei. I8 *— "—' QJ / ^c 6 roO 5 b-i Q. '0567 8 9 10 Diameter of major nuclei (//m) Figure 2. Diameters of partial nuclei measured in living unfertilized binucleate eggs. The diameters of smaller nuclei are plotted (open circles) on a cubic scale against the diameter of larger nuclei also on a cubic scale. Data are from a batch of eggs from a single female. The area between two diagonal lines ("9" and "10") indicates the domain within which the summed volumes of major and minor nuclei is equal to a sphere with a
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
