SEM observations of the membranous structure of eggs from Taenia solium.

The shell of Taenia eggs are easily ruptured and lost if the eggs are prepared according to routine methods for SEM observation. As a result, only the vitelline layer is normally seen. When the uterus is fractured while frozen, the eggs located in the lateral uterine branches are exposed and do contain intact shells. In the fully developed eggs of T. solium, six layers surround the oncosphore. Starting from the outermost structure, they are the egg shell, the vitelline layer, the outer embryonic membrane, the middle embryophoric block layer, the inner basal membrane and the oncosphoral membrane, Numerous lacunae and capillaries from a fine tubular system in he embryophore. The functional significance of these structures is discussed. In addition two structures, which can be used to distinguish eggs of T. solium from those of T. saginatus are presented.