PARENT SESSION
Oral Session # 27: Wetland Ecology II: Amphibians, Chemical Cycling, and Tidal Forests.
Presiding: D Jenkins
Tuesday, August 5. 1:30 PM to 5:00 PM, SITCC Meeting Room 101.
Amphibian malformations and parasite infection: An emerging disease?
Johnson, Pieter*,1, Lunde, Kevin2, Zelmer, Derek3, Werner, Kirwin4, 1 Center for Limnology, Madison, WI, USA2 The Roberts Environmental Center, Claremont, CA, USA3 Department of Biological Sciences, Emporia, KS, USA4 Department of Environmental Sciences, Pablo, MT, USA
ABSTRACT- Widespread reports of malformed amphibians have generated concern over the possibility of an emerging threat to amphibians and other wildlife. Recent field and laboratory evidence has implicated infection by a trematode parasite (Ribeiroia ondatrae) as an important cause of such deformities. Prior to 1999, however, there were no records of Ribeiroia from wild-caught amphibians. Whether these parasite-induced malformations represent a new or expanding phenomenon in wetland habitats remains conjectural. I investigated the causal role of Ribeiroia infection in nine North American wetlands that historically (1946-1988) yielded high frequencies of severe malformations in amphibians. Amphibian voucher specimens corresponding to these sites were redescribed using current malformation terminology and dissected to isolate trematode metacercariae. Between 1999 and 2002, historical malformation sites from California, Colorado, Idaho, Mississippi, Montana, Ohio, and Texas were resurveyed for deformed amphibians and the presence of Ribeiroia. Malformation patterns were compared with data presented in the original historical accounts and with recent reports from the western USA. Direct identification and classification by discriminant function analysis indicated that historical malformations at six of eight sites were associated with infection by Ribeiroia, dating back as far as 1946. Malformations recorded historically at these sites were consistent with the documented effects of Ribeiroia infection, including extra limbs, cutaneous fusion, and bony triangles. Of the six sites that still supported amphibians upon resurvey, three continued to support severe limb malformations at frequencies of 7 to 50% in one or more species. Although no pesticides were detected, amphibians from each of these sites were infected with Ribeiroia metacercariae. The disappearance of amphibian populations at four of the five sites associated with Ribeiroia raise concerns about possible long-term impacts of infection and malformations. Taken together, these results suggest that Ribeiroia infection has historically been an important cause of mass malformations in amphibians.
Key words: amphibian, Ribeiroia ondatrae, parasite, emerging disease