On the mechanics of growth and morphogenesis in hydroid polyps

Abstract

The growth and morphogenesis of Obelia loveni and Dynamena pumila asexual generation were studied. Their cell layers consist of tightly packed cells which are able to contract, to feorlent and slide upon one another while remaining at the same time anchored to elastic enveloping membranes. Both growth and morphogenesis are of pulsatory character due to coordinated periodic contractions and relaxations of cells. Cell contraction results in a normalization of cell orientations, an upward shift of the entodermal column, and an expansion of the rudiment's tip. Cell relaxation is accompanied by reverse deformations and an upwards shift of the ectodermal column. The spatial pattern of active and passive forces and supporting structures is ascertained. Copyright © 1974 by the American Society of Zoologists.