Pathobiology associated with the spiruroid nematodes Camallanus oxycephalus and Spinitectus carolini in the intestine of green sunfish, Lepomis cyanellus.

The histopathology induced by Camallanus oxycephalus and Spinitectus carolini in the intestine of green sunfish Lepomis cyanellus was examined. At what is assumed to be more recent attachment sites, penetration of C. oxycephalus was restricted to the mucosal layer, causing complete destruction of the columnar epithelium. At what appeared to be older attachment sites, the parasite penetrated deep into the intestinal wall, even to the circular muscle layer. At these sites of attachment, there were flask-shaped ulcers in the mucosal and submucosal layers. Surrounding the ulcers, there was granulomatous tissue, with extensive fibrosis at the surface; the fibrosis probably reduced the loss of body fluids and blood cells from the intestinal wall. The number of goblet cells in the posterior end of the intestine increased significantly, from 92.6 cells/mm in uninfected fish to 168.4 cells/mm in fish infected with more than 5 C. oxycephalus. Adult S. carolini also causes severe damage to the intestinal wall of green sunfish. Parasite penetration was not limited to the mucosal layer. Mature worms were observed invading both the muscular and serosal layers. Penetration by the parasite was usually associated with the local loss of columnar epithelium and infiltration by lymphocytes and granulocytic leukocytes. Fibrosis in the mucosal layer was commonly observed. There was goblet cell hyperplasia in the anterior portion of the intestine, with numbers of goblet cells increasing from 64.4 cells/mm in uninfected fish to 95.0 cells/mm in heavily infected fish.

The distribution and pathobiology of Neoechinorhynchus cylindratus in the intestine of green sunfish, Lepomis cyanellus.

The status of bluegill (Lepomis macrochirus) and green sunfish (Lepomis cyanellus) as homologous hosts for the acanthocephalan Neoechinorhynchus cylindratus was experimentally determined. It was found that the adult parasite did not establish in bluegills, but that these fish could serve as paratenic host. In contrast, complete growth and development to the adult stage occurred in the green sunfish. When green sunfish were intubated with 10 cystacanths/fish, the parasite exhibited a clear preference for the anterior half of the intestine; when 50 cystacanths/fish were intubated, the parasites showed a preference for the posterior half of the intestine. With repeated exposure of cystacanths, the parasites were distributed throughout the intestine. The extent of histopathology induced by N. cylindratus was related to the numbers of parasites present. In light infections (10 cystacanths), the parasite penetrated deeply into the intestinal wall and connective tissue developed around the proboscis. In infections with 50 cystacanths, the proboscis penetration was shallow and little if any connective tissue accumulated. There was also an indication that in crowded areas, the parasites appeared to change their sites of attachment frequently. In both heavy and repeated infections, the parasites evoked significant goblet cell hyperplasia and substantial quantities of mucus covered the intestinal wall. It is suggested that the sticky covering and the presumed presence of antibodies in the mucus combined to create a protective barrier thereby reducing the numbers of parasites that could attach and become established.