Document Type



frog developmental abnormalities, parasites and limb abnormalities, frog trematodes


This study is the first report of statistically significant relationships between limb abnormalities and trematode metacercariae in natural populations of frogs. We examined only parasite associations and did not investigate numerous potential pollutants that have been suggested by others to be associated with frog limb abnormalities. Rana catesbeiana of varying ages with a variety of limb abnormalities were found during the flood of 1993. By June 1994, the receding flood waters had left four pools, each with newly metamorphosing bullfrogs. Only one of the pools contained abnormal individuals and histological examination revealed significantly greater prevalence of trematode metacercarial infection in these frogs. Random tissue samples showed that within that pool, abnormal bullfrogs were significantly more likely to carry trematode metacercariae than were normal bullfrogs. Comparison of infected frogs from the study area showed that abnormal bullfrogs had significantly more severe infections than did infected normal bullfrogs. Samples of limbs abnormally lacking musculature, carried parasites while normal limbs did not and bullfrogs lacking back limbs always had subcutaneous metacercariae where the missing limb should have emerged. While this work indicates an association between parasites and limb abnormalities, it does not exclude the "easy target" hypothesis where by a chemically injured animal or chemically injured tissue might be more likely to be infected than a normal animal or normal tissue. Potential senerios are presented for both an "easy target" hypothesis and a "parasite cause" hypothesis. Our work suggests that trematode-abnormality relationships become evident only when samples are limited to metamorphosing frogs.

Publication Date

September-December 2000

Journal Title

Journal of the Iowa Academy of Science





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© Copyright 2000 by the Iowa Academy of Science, Inc.



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