Gregarine attachment organelles — structure and permeability of an interspecific cell junction

Abstract

The junction between the gregarine trophozoiteNematocystis magnaSchmidt and an epithelial cell of its earthworm hostLumbricus terrestrisMuller consists of an extensive folding and meshing of the single trilaminar membrane bounding the host cell and the complex folded multilaminar limiting membrane of the trophozoite. They are separated by a structureless intercellular region of some 50 nm in width. Specialized communicating regions or permeable elements were not observed. Transport of a radioactive label across non-junctional and junctional membranes was demonstrated by using tritiated glucose. The attachment organelle of the trophozoite is shown to be capable of allowing metabolites to pass into the cell directly from the host tissue.