Schistosoma mansoni: Development of acetabular glands of cercaria at ultrastructural level

Cercariae of Schistosoma mansoni in daughter sporocysts in Biomphalaria glabrata were studied with the electron microscope to observe the maturing process of their acetabular glands. The undifferentiated acetabular gland displays its enlarged basal area (fundus) and extended narrow process (duct) before other organ systems are recognized. Its fundus contains a prominent nucleus and subcellular organelles typical of active secretory cells.The secretory granules of the postacetabular glands are formed in a milieu of dilated rough endoplasmic reticulum and Golgi. Two morphologically different secretory granules are produced: (1) homogeneously granular ones, and (2) other granular ones with electron dense bodies in their matrices. Mostly, the homogeneously granular ones are produced first in the fundus and are forced into the ducts as the other type is formed.The secretory granules of preacetabular glands are formed from translucent vacuoles which arise from an environment of endoplasmic reticulum and Golgi. Two morphologically different secretory granules are produced: (1) one type has a homogeneous dense matrix, and (2) the other type has a less dense matrix containing electron-lucid bodies.The duct of an undifferentiated acetabular gland has either filamentous material or microtubules dispersed in its cytoplasm. Once microtubules are formed, they persist during the life of the cercaria. The microtubules are believed to have possibly two functions: (1) to support the long duct, and (2) to assist the movement of the secretory granules into the channels of the ducts where they remain until released during host penetration.Few of the subcellular organelles associated with secretory granules formation are seen in the duct except the area in close proximity to the fundus; thus, the few secretory granules produced in the duct are in this region.