Ultrastructural aspects of ecdysis in the naked dinoflagellate Amphidinium carterae

Abstract

The stressor-induced ecdysis takes a special place in dinoflagellate biology. During ecdysis, a cell loses the plasmalemma, outer amphiesmal vesicle membrane and, in armored species, thecal plates, becomes immotile, and then amphiesma regeneration occurs. Here we report the results of our study of cell covering rearrangement during ecdysis in the naked dinoflagellate species Amphidinium carterae Hulburt 1957. Ecdysis was induced by mechanical treatment (centrifugation). The changes in cell organization at the ultrastructural level were examined using transmission electron microscopy methods. Shedding of the plasma membrane and the outer amphiesmal vesicle membranes, fusion of the inner amphiesmal vesicle membranes were observed. The amorphous cytoplasm zone, which underlies inner amphiesmal vesicle membranes in motile cells, retains under the new plasma membrane in ecdysed cells. We showed accumulation of small vesicles and flattened tubules that apparently begin fusion to form juvenile amphiesmal vesicles in this zone. The absence of pellicle in Amphidinium dinoflagellates was suggested.