The influence of cell interactions and tissue mass on differentiation of sea urchin mesomeres*

Open Access
Publisher Website
Google Scholar
Abstract
The developmental potential of different blastomeres of the sea urchin embryo was re-examined. We have employed a new method to isolate substantial numbers of different kinds of blastomeres from 16-cell-stage embryos, and we have used newly available molecular markers to analyze possible vegetal differentiation. We have found that, while isolated mesomere pairs behave according to the classical expectations and develop into ectodermal vesicles, there is a clear effect of reaggregat ing two or more mesomere pairs. They survive better in long-term culture and, after prolonged periods, they display an astonishing ability to express vegetal differen tiation. We also combined mesomeres with stained micromeres or macromeres from the vegetal hemi sphere. Although induction of guts and spicules was observed, there was little if any effect of varying the ratio of different blastomeres on the kinds of differentiation obtained.