Pathogenic fungus in feral populations of the invasive North American bullfrog in Argentina

Abstract

Nearly a third (32.4%) of the world?s amphibian species are either threatened with extinction or already extinct (1). The chytrid fungus Batrachochytrium dendrobatidis (Bd) (Chytridiomycetes: Ryzophydiales) (2) has been recognized as responsible for mass mortalities or population extinctions of numerous anuran species in different continents (e.g., 3,4,5 and citations therein). There is evidence that legal and illegal trade in amphibians as pets, food and for bio-control is one of the reasons for the spread of Bd (6,7,8,9).The North American bullfrog, Lithobates catesbeianus (Shaw, 1802) (Anura: Ranidae), has been introduced accidentally or intentionally for aquaculture into numerous countries (10). L. catesbeianus is a highly invasive species that disperses rapidly within an ecosystem (11). The oldest report of specimens of L. catesbeianus parasitized by Bd dates from 1928, and corresponds to individuals from the State of California, USA (12). Bullfrogs can be asymptomatically infected with Bd (13), and infected specimens can readily spread the disease into new geographic regions (14).Initial unsuccessful attempts to introduce bullfrogs into Argentina for farming date from 1935. A subsequent successful introduction occurred during the 1980s (10,15). Escaped individuals became established and the species spread rapidly (16). Nevertheless assessments of the presence of Bd in feral bullfrogs from Argentina are lacking (17,18).