Presence of a protrusion on the ventral disk of adhered trophozoites of Giardia lamblia

About 30% of the trophozoites of Giardia lamblia, fixed while adherent to t he substrate using fixative solutions designed to better preserve cytoskele tal elements, showed the presence of a ventral disk. This structure varied in shape and size and could be seen by scanning and transmission electron m icroscopy, as well as by confocal laser scanning microscopy of cells incuba ted with 3-3'-dihexyloxacarbocyanine iodide, which labels cisternae of the endoplasmic reticulum. It could also be observed in living adherent cells. A row of microtubules, a large number of glycogen particles, peripheral ves icles and concentric membranes were seen within the protrusion.