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E-M:/ Media Advisory: Amphibians and Crippling Parasites

Enviro-Mich message from "Anne Woiwode" <anne.woiwode@sierraclub.org>

>From the Ecological Society of America -- note that the article says
increased numbers of the parasites discussed are associated with
artificially created wetlands and suspected to be associated with nutrient
pollution from fertilizers and cattle.  AW

-----Original Message-----
From: Ecological Society of America: Society News and Business Only
[mailto:ESANEWS@LISTSERV.UMD.EDU]On Behalf Of David Inouye
Sent: Thursday, April 18, 2002 7:38 PM
Subject: Media Advisory: Amphibians and Crippling Parasites

Ecological Society of America
1707 H Street, NW, Suite 400
Washington, DC 20006
For immediate release
April 18, 2002
Amphibians and Crippling Parasites
New study links parasite to amphibian malformations in western U.S.

In recent years, the frequency of malformed frogs, toads, salamanders
and other amphibians found with missing limbs, extra limbs, and skin
webbings has increased. The shrinking populations of many North
American amphibian populations underscore the need to understand the
causes and implications of this phenomenon. Now a new study suggests
that a parasite may be to blame for many of the abnormalities found in
amphibians of the western United States.

In the research article "Parasite (Ribeiroia Ondatrae) infection linked
to amphibian malformations in the western United States," appearing in
the May issue of the Ecological Society of America's journal Ecological
Monographs, Pieter Johnson of the University of Wisconsin-Madison and
colleagues describe the results of their broad-scale field survey.
Covering parts of California, Oregon, Washington, Idaho, and Montana,
the team of researchers looked for malformations in over 12,000
amphibians representing 11 species of amphibians. The group looked at
the relationships between the frequency and severity of abnormalities
and a variety of factors in a particular aquatic site, including the
abundance of a parasite (Ribeiroia) and pesticide contamination.

The collaborative and interdisciplinary effort, which included academic
researchers, as well as federal scientists from the U.S. Geological
Survey and the U.S. Fish and Wildlife Survey, found malformed amphibians
at a wide variety of aquatic sites, ranging from montane lakes and
ephemeral pools to irrigation canals and impoundments. While the
researchers did not find a relationship between pesticides and the
frequency of malformed amphibians, they did find a striking connection
between malformed amphibians and the presence of Ribeiroia.

"The presence of this parasite was a powerful predictor of the presence
and frequency of malformed amphibians in an aquatic system. The greater
an amphibian population's infection with Ribeiroia, the more frequent
and severe the population's limb malformations," said Johnson.

Amphibians at sites supporting the parasite exhibited 6 times as many
abnormalities as the average number of malformations recorded at sites
without the parasite. The researchers found the parasite embedded
around the base of amphibians' limbs and tails, where they form cysts
beneath the skin. The frequency of abnormalities varied substantially
among sites and species, ranging from 0 to nearly 90 percent. Pacific
treefrogs (Hyla regilla) exhibited the greatest number of abnormalities,
with more than 1000 abnormal tadpoles and young frogs found at 55 sites.
When they co-occurred at an aquatic site, Pacific treefrogs exhibited
more abnormalities than did western toads, marginally more than
bullfrogs, and less than California newts.

In order to understand if and why the parasite may have become more
common in recent years, the research team also gathered information on
the ecology and life history of Ribeiroia, which has a multi-host life

The paper notes that the final stage of the parasite's life cycle is
dependent upon predation; in order to complete its final developmental
stage, the parasite depends upon a bird or mammal to eat an infected
amphibian or fish. The parasite then sexually matures and releases eggs
via bird or mammal feces. When the eggs hatch they invade the tissue of
Planorbella, an aquatic snail.

The study revealed that this aquatic snail is a significant indicator
of both the presence and abundance of the parasitic infection. The
presence and abundance of this snail were the only two factors related
to the presence or abundance of Ribeiroia.

The researchers note that both Planorbella and increased parasitic
diseases are associated with artificially created wetlands, which have
been on the increase, often replacing natural wetlands.
"People assume that parasites are "natural" and therefore of no
conservation concern," says Johnson. "However, we suspect that nutrient
pollution from fertilizers and cattle may be increasing the numbers of
snails, parasites, and therefore malformed amphibians."

Johnson notes that the parasite may be of particular concern to
declining amphibian populations, such as Western Toads and Columbia
Spotted Frogs, which were often found infected and malformed.
**Photos are available for this story at:


Contact Steve Holt at sh@stockpix.com or 541.267.2803 for reprint

Founded in 1915, the Ecological Society of America (ESA) is a
scientific, non-profit, organization with over 7500 members. Through ESA
reports, journals, membership research, and expert testimony to
Congress, ESA seeks to promote the responsible application of ecological
data and principles to the solution of environmental problems. For more
information about the Society and its activities, access ESA's web site
at: www.esa.org.

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