Observations on the intestinal pathology caused by three caryophyllid tapeworms of the white sucker Catostomus commersoni Laécpéde

The structure of the parasite‐host interface at the site of attachment was studied for Glaridacris catostomi, G. laruei and Hunterella nodulosa, caryophyllid tapeworms of the white sucker Catostomus commersoni. Light microscope observation of fish infected with H. nodulosa showed a loss of intestinal epithelium and lamina propria, and a chronic inflammatory response characterized by infiltration of lymphocytes and extensive hyperplasia of the submucosal tissue; intestinal pathology associated with G. catostomi and G. laruei was minimal. Electron microscope examination of the parasite‐host interface revealed that in no case does parasite tissue come into direct contact with host tissue. H. nodulosa is separated from host tissue by an amorphous layer of electron lucent material (the ‘eosinophilic matrix’ seen with the light microscope) which appears to act as an adhesive; this material is a secretory product of the scolex glands. In G. catostomi and G. laruei a layer of material separating parasite from host tissue was also found, but it is not clear whether this layer is adhesive or protective.