In defecation, when a spent vacuole has fused with the single membrane along the midline of the ridge the lips of the cytoproct split apart and form a wide gap. The membrane of the spent vacuole is now continuous with the plasma membrane and quickly undergoes vesiculation into vesicles that are released back into the cytosol. No membrane is released into the surrounding environment. The cytoproct lips are covered by extensions of alveoli up to their tips. Complete defecation is insured by the retrieval of all of the spent vacuole membrane until the lips are pulled back together at the tip of the ridge and all DV-IV membrane has been removed from the cytoproct. No other expulsion force is needed for expelling the vacuole contents. TEM taken on 5/25/82 by R. Allen with Hitachi HU11A operating at 60kV. Neg. 6,500X. Bar = 1?m. The negative was printed to paper and the image was scanned to Photoshop. This digitized image is available for qualitative analysis. An unprocessed, high resolution version of this image (CIL:38701) is in the library and available for quantitative analysis. Standard glutaraldehyde fixation followed by osmium tetroxide, dehydrated in alcohol and embedded in an epoxy resin. Microtome sections prepared at approximately 75nm thickness. Additional information available at (http://www5.pbrc.hawaii.edu/allen/).
Biological Process: Cortical cytoskeleton organization, Defecation
Author: Richard Allen (University of Hawaii)
Source: The Cell: An Image Library