Triaenophorus in situ

This photo shows various high-magnification cross sections of intestine of a northern pike that harbored numerous adult T. crassus. The parasite uses hooks on its scolex to attach firmly to he intestinal wall, and stimulates a pronounced but localized reaction by the host's tissues.

The upper left photo shows a region of intestine that is relatively normal on the left, but has a single scolex attached in the middle. This is probably a recently-attached worm, because there are still intact villi surrounding it. Note, however, that the parasite has caused an ulcer at the site of attachment. Beneath the scolex the intestine is inflamed. The dark staining is a result of numerous host defense cells that have migrated to the tissues near the site of attachment. At the right of the section is a raised nodule. The villi on it are eroded and the parasites scolex is present near the centre of the nodule.

The lower left photo shows details of the host-parasite interface. The scolex and one of its hooks are at the upper right of the photo. Host tissue is lower left, and all the dark spots are nuclei of cells. Among these cells are many fibroblasts which deposit connective tissue at the site of the injury.

At the right is an intestinal section taken near the one in the upper left, but stained with a special stain that stains connective tissue red, but all other tissues yellow. The thin band of red in the centre of the photo is the normal stratum compactum of the pike intestine. Below it, in the muscle layer, you can see that there has been extensive connective tissue deposition (= scarring). Above it, you can see that the thickening of the intestine is also accompanied by extensive connective tissue deposition.