. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PARTHENOGENESIS IN STARFISH EGGS 527 of the fertilization membrane in most eggs at any maturation stage after germinal vesicle breakdown (GVBD), just as the oocytes are fertilizable at any stage. The fertilization membrane became visible a few minutes after the application of caffeine, and elevated slowly taking several tens of minutes as in normally fertilized eggs. The formed membrane appears to be intact (Fig. 4A). Concurrently with the elevation of the fertilization membrane, oxygen consumption of the treated eggs increa
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. PARTHENOGENESIS IN STARFISH EGGS 527 of the fertilization membrane in most eggs at any maturation stage after germinal vesicle breakdown (GVBD), just as the oocytes are fertilizable at any stage. The fertilization membrane became visible a few minutes after the application of caffeine, and elevated slowly taking several tens of minutes as in normally fertilized eggs. The formed membrane appears to be intact (Fig. 4A). Concurrently with the elevation of the fertilization membrane, oxygen consumption of the treated eggs increased tran- siently as in normal fertilization (Nemoto, Washitani, and Hino, in prep.). The term "activation" here means formation of the fertilization membrane by caffeine and other methylxanthines. The formation of the fertilization membrane following 10 mM caffeine treatment was inhibited by 4-6 mM procaine which suppresses the breakdown of the cortical granules of fertilized sea urchin eggs (Vacquier, 1975). Other methylxanthines, such as theophylline and theobromine, had the same effects (Fig. 1B). Two mA/ isobutyl-methylxanthine also activated about 30% of the treated eggs. Owing to low solubility in NSW, however, the effects at higher concen- trations could not be examined. Asterias amurensis and Astropecten scoparius eggs were also activated by these methylxanthines under similar concentrations (data not shown). Such effects of these methylxanthines were independent of Ca2+ in the external medium (Fig. 1A, B). Duration of treatment with caffeine necessary to induce cleavage The treatment with methylxanthines for a few minutes activated eggs as seen by elevation of a fertilization membrane; longer treatment allowed eggs to develop further if the eggs were returned to NSW after the treatment (see Figs. 4 and 5). In the experiments shown in Figure 2, caffeine (8 or 10 mM) was applied to eggs between first and second polar body formation. Fifty to ninety minute trea
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
