Stage Specific Effects on Sea Urchin Embryogenesis of Zn

Treatment of sea urchin embryos for 3 hr starting at the 16-64 cell stage with Li+ or 3-isobutyl-1-methylxanthine as well as with other inhibitors of cAMP-phosphodiesterase (PDE) and several inhibitors of protein synthesis, resulted in production of vegetalized embryos with a large exogut. However, the same treatment starting at other stages produced hardly any vegetalized embryos. The specific stage for these substances to cause vegetalization is probably the 16-64 cell stage. Treatment with Zn2+ between the times of fertilization and hatching, followed by culture in normal sea water produced animalized embryos with little if any archenteron, but the same treatment followed by culture with ethylenediamine-N, N'-diacetic acid (EDDA), a chelator of Zn2+ , produced quasi-normal plutei. This chelator did not counteract the animalizing effect of Zn2+ when culture with EDDA was started at the post-gastrula stage. Treatment of embryos for a long period (1-3 days) starting at the blastula stage with Li+ and the inhibitors of PDE and protein synthesis, as well as with Zn2+ , produced spherical embryos with little or no archenteron. The stages at which these substances produced abnormal embryos with a poor archenteron are post-hatching stages.