preceded_by Platynereis life cycle stage zygote stage cleaving embryo stage 2-7 cle At a temperature of 18 C this stages lasts from 2.00 hours till 7.00 hours. Developmental stage following Zygote stage with the following key events: Spiral cleavage pattern with individually identifiable blastomeres. First and second cleavage inequal and meridional. Third cleavage forms micromeres and macromeres. Ends with the appearance of the fourth quartette of micromeres. PdumDv:0000200 UBERON:0000107 platynereis_stage