. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PARTHENOGENESIS IN SEA CUCUMBERS 385 face. The disintegrated germinal vesicle was not reconstructed into its original shape. No elevation of the fertilization membrane was observed, up to 30-50 min after the start of DTT treatment. A proportion of DTT-treated, unfertilized oocytes whose germinal vesicles had been broken precociously were found to develop parthenogenetically (Fig. 2). Figure 3 shows relationships between the time of pipetting and the frequency of blastulae or gastrulae that were induced to develop parthenogen
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PARTHENOGENESIS IN SEA CUCUMBERS 385 face. The disintegrated germinal vesicle was not reconstructed into its original shape. No elevation of the fertilization membrane was observed, up to 30-50 min after the start of DTT treatment. A proportion of DTT-treated, unfertilized oocytes whose germinal vesicles had been broken precociously were found to develop parthenogenetically (Fig. 2). Figure 3 shows relationships between the time of pipetting and the frequency of blastulae or gastrulae that were induced to develop parthenogenetically. The efficiency of pipetting in triggering this development was time-dependent. Pipetting at 10 min after the start of DTT treatment gave the maximum efficiency; 20-77% of the pipetted oocytes developed parthenogenetically. Pipetting of intact oocytes at 20 min before DTT treatment was also effective in some batches of oocytes (Fig. 3). However, pipetting at the stages after the normal germinal vesicle breakdown had no effect in triggering the development; these eggs became fragmentated after two cycles of meiotic division. In the following experiments, pipetting was made routinely at about 10-11 min after the start of DTT treatment. When maturation of oocytes pipetted at 10-11 min following DTT treatment was observed with time-lapse cinematography, the residue of the germinal vesicle material could be distinguished from the surrounding cytoplasm as a clear area. At 15-20 min after the start of DTT treatment (corresponding to the stage of germinal vesicle migration in control oocytes), the residue of the ruptured germinal vesicle in the pipetted oocytes also migrated to the micropyle process. Almost coincidently, a transparent cytoplasmic spot (termed "clear spot") was formed in. FIGURE 2. Parthenogenetic development of pipetted, DTT-treated oocytes. Oocytes were treated with DTT and then pipetted at 10-11 min after the start of DTT treatment. A: oocyte immed
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
