Modification of the ultrastructure of the muscle larva of Trichinella pseudospiralis following exposure to acidified pepsin solution.

Examination of the cuticle of Trichinella pseudospiralis by transmission electron microscopy revealed an epicuticle, exocuticle, and mesocuticle, each divided into several layers. The epicuticle consisted of an outermost thin plasmalemmalike infracuticular material covering an inner trilaminar membrane. The exocuticle was granular and could be divided into 2 regions on the basis of density. The mesocuticle was fibrillar and 3 regions could be distinguished based on the orientation of fibrils. The cuticle appears attached to the hypodermis by hemidesmosomes. The infracticular structure was altered following isolation of larvae by pepsin-HCl digestion of host muscle.