Ultrastructural studies on the plerocercoid of Spirometra erinacei in experimental sparganosis

The gland cell and the tegument of the Spirometra erinacei plerocercoid following parasite migration in hamsters were observed by electron microscopy. Gland cells released secretory granules mainly into the frontal pit during each stage of migration. The density of the perinuclear secretory granules decreased markedly just after parasite penetration through the host intestinal wall. Therefore, gland cells seem to play an essential role in penetration. During migration in the host, lipid-like droplets appeared in the subtegumental cells and tegument and increased in number and size during migration in the abdominal cavity, but they had disappeared from plerocercoids recovered from subcutaneous tissues. Myelin-like bodies also occurred in the tegument, subtegumental cells and medullary matrix; they were released directly through the tegument into the frontal pit. Discoidal bodies gathered in the distal part of the tegument, where filamentous microtriches appeared in regions from which microtriches had been peeled off during penetration.