The fine structure of ceratium tripos, a marine armored dinoflagellate: I. The cell covering (theca)

Abstract

In this, the first of three consecutive papers, the complex cell covering of Ceratium tripos is examined at different stages of development. During cytokinesis, the cleavage furrow is surrounded by a system of membranes which, together with the thecal plates, will comprise the future cell covering. The outermost membrane completely surrounds the cell and lies over a single layer of large flattened vesicles. An additional membrane, the thecal membrane, lies within the vesicles just below the region of eventual plate formation. The thecal membrane gradually becomes discontinuous in mature cells. Sutures are observed during the initial differentiation of the cell covering. Near the completion of cytokinesis, the portion of cytoplasm still joining the daughter cells is enclosed by only one membrane of the cell covering, the plasma membrane.