Ultrastructure of the pellicle of Euglena gracilis

Deep-etching technique was used to investigate the organization of the pell icle complex of Euglena gracilis. The interpretation of the images was furt her supported by SEM and TEM investigations. Our results mainly validate data obtained by previous freeze-fracture studi es on the E and P faces of the outer cortical membrane. At the level of the ridges, the outer E fracture face is highly organized in a regular striate d pattern, whereas the P inner face shows a particulate structure. However, our images reveal that this particulate organization of the P face is not limited to the ridges, but it is displayed also by the grooves. Moreover, t his face shows two distinct layers, a particulate layer facing the cytoplas m and a striated layer facing the E face; these layers represent different true fracture levels of the same P face. (C) 2000 Harcourt Publishers Ltd.