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The great abundance of snails parasitized by larval stages of digenetic trematodes in the Okoboji region in northwest Iowa makes this area a particularly interesting one for helminthological investigations. Lymnaea reflexa (Say), an aquatic snail found in large numbers in ponds near the Lakeside Laboratory on West Lake Okoboji, show a remarkably high percentage of infection with strigeid metacercariae of the tetracotyle type. In some areas, collections of several hundred snails showed upon examination that 100 per cent were parasitized with developing and fully formed tetracotyles. These metacercariae, which are usually present in great number within the hermaphroditic gland of the infected snail are occasionally found, too, within rediae of other species of trematodes parasitizing the same snail. Of 425 Lymnaea reflexa collected and examined during the summer of 1954, 419 were parasitized by one or more species of trematodes. Of these parasitized snails, 163 contained fully formed encysted tetracotyles, 243 harbored tetracotyles in various stages of development, and 12 snails were doubly infected with echinostome rediae as well as tetracotyles. One Lymnaea reflexa gave evidence of a triple infection, since echinostome metacercariae, tetracotyles in all stages of development, and trichocercous cercariae were found in it upon dissection.

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Proceedings of the Iowa Academy of Science





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© Copyright 1955 by the Iowa Academy of Science, Inc.



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