Acute toxic effects of two lampricides on twenty-one freshwater invertebrates
We conducted laboratory static bioassays to determine acute toxicity of two lampricides -- a 70% 2-aminoethanol salt of 5,2'dichloro-4'-nitrosalicylanilide (Bayer 73) and a mixture containing 98% 3-trifluoromethyl-4-nitrophenol (TFM) and 2% Bayer 73 (TFM-2B) -- to 21 freshwater invertebrates. LC50 values were determined for 24-h exposure periods at 12.8 C. Organisms relatively sensitive to Bayer 73 were a turbellarian ( Dugesia tigrina ), aquatic earthworms ( Tubifex tubifex and Lumbriculus inconstans ), snails (Physa sp.) and ( Pleurocera sp. ), a clam ( Eliptio dilatatus ), blackflies ( Simulium sp. ), leeches ( Erpobdellidae ), and a daphnid ( Daphnia pulex ). The invertebrates most sensitive to TFM-2B were turbellarians, aquatic earthworms ( Tubifex ), snails ( Physa ), blackflies, leeches, and burrowing mayflies ( Hexagenia sp. ). Bayer 73 was generally much more toxic to the test organisms than TFM-2B. At lampricidal concentrations, TFM-2B was more highly selective than Bayer 73 against larval sea lampreys ( Petromyzon marinus ).