Ultrastructure studies of Proteocephalus longicollis (Cestoda, Proteocephalidea]: transmission electron microscopy of scolex glands

The ultrastructure of two types of secretory glands in the scolex of preadu lts of Proteocephalus longicollis is described for the first time in the pr esent report. The gland cells contain extensive cisternae of granular endop lasmic reticulum and Golgi complexes, which participate in the production o f secretory globules. Type I scolex glands produce electron-dense globules of various size. The secretory globules enter the secretory canal, openings of which were not observed in the preadults. The secretory product of type I was found at the inner sucker surface and in the tegument of the sucker edges. In addition, electron-dense globules in adult worms are secreted via an eccrine mechanism. Type II scolex glands are characterized by secretory globules of lower electron density and occur mainly in preadults. The elec tron-lucent, membrane-bound secretory globules are transported via microtub ule-lined ducts opening to the exterior at the tegumental surface. Secretor y globules of type II are released by an eccrine process.