Cytotoxicity of the field lampricide 3-trifluoromethyl-4-nitrophenol (TFM) in tadpole cell lines from North American frogs.

The common field lampricide, 3-trifluoromethyl-4-nitrophenol (TFM), is used to treat streams and creeks infested with highly invasive and destructive sea lamprey (Petromyzon marinus) in the tributaries of the Great Lakes. Unfortunately, amphibian deaths have been reported following stream treatments with TFM. Larval amphibians (tadpoles) are more susceptible to TFM toxicity than adult amphibians. The aim of this study was to test the toxicity of TFM in eight new tadpole cell lines from the green frog (Lithobates clamitans), wood frog (Lithobates sylvaticus), and American toad (Anaxyrus americanus). A cell viability bioassay using two fluorescent dyes, Alamar Blue and CFDA-AM, was performed following 24-h and 72-h exposures to a range of TFM concentrations. In general, TFM exposure reduced Alamar Blue fluorescence more rapidly than CFDA-AM fluorescence in tadpole cells, suggesting that Alamar Blue is perhaps a better diagnostic indicator of cell health for acute TFM cytotoxicity. At present, the in vivo 96-h LCs of TFM are only available for L. clamitans and they correlated well with the in vitro EC values for the green frog tadpole cell lines in this study. The eight tadpole cell lines with different relative sensitivities to TFM cytotoxicity could prove to be useful tools in assessing next-generation lampricides in high-throughput bioassays to ensure safety in frogs before their sea lamprey-targeted application in the field.