Evans blue treatment promotes blastomere separation and twinning in Lytechinus pictus embryos

Demembraned Lytechinus pictus embryos briefly treated with the dye Evans Blue during the first cleavage division subsequently showed frequent blastomere disengagement leading to development of twinned embryos. Further development of twinned embryos was observed in hanging drops and in batch cultures. The timing of micromere production was disturbed in some twinned embryos, but this disturbance was not correlated with subsequent developmental problems. Many twinned embryos resulting from blastomere separation following Evans Blue treatment developed into small but normal-appearing plutei.