The hatching mechanism of the egg of Fasciola hepatica L.

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Abstract
The hatching mechanism of the liver fluke egg was investigated and a new interpretation put forward. Light stimulates the miracidium and, when fully activated, the miracidium is responsible for altering the permeability of the membrane on the internal concave surface of the viscous cushion. Prior to expansion the cushion (a fibrillar mucoprotein complex) is in a dehydrated or semihydrated state. The change in permeability of the enclosing membrane allows the fluid egg contents to permeate into the cushion. The fibrillar matrix becomes hydrated and an increase in volume occurs. This compresses the miracidium and sacs and an internal pressure is set up which gradually increases until the operculum finally ruptures and flies back violently. The cushion and miracidium are then expelled by the hypertonicity of the egg contents.I would like to thank Professor O. W. Richards, in whose department this work was carried out, also Dr F. Call and Professor B. G. Peters for their many helpful criticisms. I am also grateful to Miss Mary Morris for assistance with the electron microscopy.