AbstractsBiology & Animal Science

The fish of Suttle Lake, Oregon, have been found to harbor an acanthocephalan parasite, which lives attached to the mucosa of the intestine. Between July 1961 and January 1963, several hundred of these fish were exarnined and nearly every one was infected with this parasite, which was identified as Neochinorhynchus rutili (Mueller, 1780). Since relatively little is known about the life cycle and post-embryonic development of N. rutili, it was decided to study these problems in the laboratory. Of 267 ostracods (Cypria turneri) examined, 64 or 24 percent were found to harbor the cystacanth or juvenile stage. Some of these ostracods were fed to two small infection-free cutthroat trout. The first fish was fed five and the second was fed nine. Two weeks later one male acanthocephalan was found established in the intestine of the first fish and four, including three females in the second. It was possible to follow the development of the parasite from the emergent embryo to the infective cystacanth. Several infection-free ostracods from a local pond were infected by allowing them to feed on shelled embryos from the body cavity of an adult worm. The ostracods were then dissected periodically and the stages of development were studied and drawn. The life cycle can be summarized in the following way. The shelled embryos are released by the adult worm into the intestinal lumen of the fish and they pass out with the feces. These "eggs" are ingested by ostracods (Cypria turneri). The embryo emerges as an acanthor and penetrates the wall of the gut into the hemocoel where it metamorphoses through acanthella to the cystacanth or juvenile stage in 48 to 57 days. This final stage is infective when eaten with the ostracod by the fish.