ABSTRACT
The stage-specific changes in the distribution pattern of microtubules were studied in the ectoderm cells of the detergent-extracted and immunocytochemically processed embryos of the sea urchin, H. pulcherrimus, using both light and electron microscopes. The localization of microtubules was observed to emerge in gastrula, reaching a peak in plutei with bundles of microtubules in the cells in the ciliary band and arm-tips. The length of the ectodermal cells showed similar changes to that of the microtubule distribution implying that the increase in microtubule density in the ectoderm cells correlates with the increase in the cell length. Nocodazole treatment of mesenchyme blastulae resulted in the disappearence of microtubules from ectoderm cells; the cell length decreased throughout the embryos. These results suggest that the local increase in the microtubule density in ectoderm cells correlates to the elongation of these cells, a possible mechanism for the shape change in the embryo.
