Evaluation of the potential effects of methoprene and Bti on anuran malformations in Wright County, MN

Abstract

An increasing number of amphibians from around the globe have been reported with deformations and malformations of the eyes, mandibles and internal organs as well as missing, abnormally shaped, abnormally pigmented, or multiple limbs. For the purposes of this document, the terms “deformation” and “malformation” are defined as in a recent USGS publication entitled, “Field Guide to the Malformations of the Frog and Toad” (Meteyer et. al. 2000a). Thus, the term deformation refers to alterations in form or structure that occur later in development, resulting from mechanical factors such as amputation. “A deformation does not involve an intrinsic defect in morphogenesis and impacts a structure that is otherwise developing normally.” The term malformation refers to “errors in any phase of morphogenesis including cell proliferation, cell migration, differentiation, programmed cell death or regression of larval structures.” This report is primarily concerned with malformations and their possible connection with the use of either methoprene or Bacillus thuringiensis var. israeliensis (Bti) in developing Rana pipiens (northern leopard frogs) in central Minnesota.