Original research paper
Ultrastructure of developing taeniid embryophores and associated structures

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Abstract

The structures surrounding the embryos of Taenia hydatigena, T. ovis, T. pisiformis, T. saginata, and Echinococcus granulosus were examined with the electron microscope. The embryophore develops from the inner surface of a faint membrane which surrounds the embryo. Circular bodies appear to be focal points around which the dense block substance is deposited. The granular material closely associated with the developing embryophoric blocks appears to be incorporated into the block substance. It is suggested that the circular bodies are somehow involved in the transformation of the granular material into the dense block substance.

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    Taeniid eggs are spherical to ellipsoid in shape and usually range in size from 30 to 50 μm and from 22 to 44 μm in their two diameters. They are morphologically indistinguishable at the light microscope level and ultrastructural studies of the eggs of E. granulosus, E. multilocularis and various Taenia species have shown that they possess similar structures consisting of several layers and membranes (Fig. 6) (Morseth, 1965; Sakamoto, 1981; Swiderski, 1982). The embryophore is the principal layer affording physical protection to the embryo, or oncosphere, since the vitelline layer (‘egg shell’ or outer envelope) is passively removed from the egg before it is liberated.

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