Upper Midwest Environmental Sciences Center
Home/ Overview/ Science Programs/ Data Library/ Products and Publications/States/ Rivers/Teachers and Students/ Links/ Contact/ Search |
Farm ponds as critical habitats for native amphibians
Daniel R. Sutherland and Joshua M. Kapfer
University of Wisconsin-La Crosse,
Department of Biology and River Studies Center,
1725 State St., La Crosse, Wisconsin 54601
Michael J. Lannoo
Muncie Center for Medical Education, MT 201
Indiana University School of Medicine
Ball State University, Muncie, Indiana 47306
and
Melinda G. Knutson
U.S. Geological Survey
Upper Midwest Environmental Sciences center
2630 Fanta Reed Road
La Crosse, Wisconsin 54603
Abstract
Metacercariae of Ribeiroia ondatrae have been shown in laboratory
and field studies to elicit significant limb malformations in metamorphs
of several amphibian species. During a five-year study of trematode metacercariae
from Minnesota and Wisconsin anurans, Ribeiroia was distributed
throughout eastern Minnesota and western Wisconsin. Ribeiroia
was most abundant (100% prevalence, mean intensity >110 worms per host)
at two Minnesota malformation hotspots during the same years that extremely
high (>50%) malformation rates occurred at the sites. Subsequent declines
in malformation rates at these two sites have been correlated with reduced
Ribeiroia abundance in metamorphs. Ribeiroia has not
been found at malformation hotspots in western Minnesota, indicating that
causes other than Ribeiroia are responsible. Preliminary studies
on malformed anurans from eastern U.S. wildlife refuges indicated that,
though infrequent, Ribeiroia is present at some sites. We suggest
that in order for high rates of malformations to occur at a site, Ribeiroia
infection rates must exceed a species-specific threshold. Environmental
conditions that support increased intermediate snail host populations
will, in turn, provide more Ribeiroia cercariae to penetrate
tadpoles at critical times during limb formation. High Ribeiroia
infection rates may elicit more frequent and severe amphibian malformations.
Keywords: Anura, malformations, parasites, Ribeiroia, Trematoda, Minnesota, Wisconsin, amphibian, deformity.
July 19, 2002