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.
Adel-Meguid
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Department of Biology, Wake Forest University, Winston-Salem, North Carolina 27109, USA.
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D000049:Acanthocephala / Q000302:isolation & purification* / Q000472:pathogenicity* / Q000648:ultrastructure; D000818:Animals; D005260:Female; D006373:Helminthiasis / Q000503:physiopathology*; D007421:Intestine, Small / Q000469:parasitology* / Q000473:pathology / Q000648:ultrastructure; D008099:Liver / Q000469:parasitology*; D008297:Male; D008855:Microscopy, Electron, Scanning; D010473:Perciformes / Q000469:parasitology*; D012727:Sex Characteristics; D013045:Species Specificity; D013997:Time Factors