Amphiesmal ultrastructure inNoctiluca miliaris Suriray (Dinophyceae)

The ultrastructure of the cell covering (amphiesma) of vegetative cells ofNoctiluca miliaris (Dinophyceae) was studied in detail using thin sections. The amphiesma is typically amphidinoid and contains the following components (starting from the outside): (a) a continuous outer membrane (plasmamembrane) surrounding the cell; (b) a layer of contiguous vesicles (amphiesmal vesicles) that contain a thin “honeycomb-patterned” layer of material appressed mainly to the outer portion of the vesicle membrane; (c) a finely granular pellicular layer that lies beneath the amphiesmal vesicles and (d) groups of cortical microtubules (only present in certain regions of the cell). The pellicular layer is always present but its thickness is highly variable (20–800 nm) depending on regional specializations of the amphiesma. Trichocysts and mucocysts project through the pellicular layer and amphiesmal vesicles, the apical portion of their limiting membrane docks at the plasmamembrane. Small vesicles that presumably contain material for the “honeycomb-patterned” layer traverse the pellicular layer through discontinuities and presumably fuse with the amphiesmal vesicles. We conclude thatNoctiluca has a typical dinophycean (i.e. amphidinoid) cell covering, and that the most recent proposal for the developmental origin of the dinoflagellate pellicle should be revised. Dedicated to Dr. Dr. h.c. P. Kornmann on the occasion of his eightieth birthday.