Schistosoma mansoni: ultrastructure of cercarial escape glands

While in the sporocyst, the cercaria of Schistosoma mansoni has a pair of unicellular escape glands whose funduses are located together on one side of the body. The funduses taper into microtubule lined ducts that open on the anterior surface of the oral sucker through desmosome supported pores in the immediate vicinity of the ducts of the acetabular glands. The glands contain membrane-bound secretory granules which have a fine medium-dense, homogeneously granular material in their matrices. A large membrane-bound reservoir of granular material, whose texture is similar to that of the secretory granules, is often seen in the cytoplasm of the funduses. In free-swimming cercariae, the ducts in the oral sucker are the only obvious remains of the escape gland.