ACUTE TOXICITY AND BEHAVIORAL-EFFECTS OF CHLORPYRIFOS, PERMETHRIN, PHENOL, STRYCHNINE, AND 2,4-DINITROPHENOL TO 30-DAY-OLD JAPANESE MEDAKA (ORYZIAS-LATIPES)

Five chemicals with different modes of action were evaluated in labora tory studies to determine their acute toxicity (48-h median lethal con centration [LC50]) and behavioral effects on 30-d-old Japanese medaka (Oryzias latipes). The order of toxicity far these xenobiotics was per methrin > chlorpyrifos > 2,4-dinitrophenol (2,4-DNP) > strychnine > ph enol. The 48-h LC50s were significantly different and ranged from 0.01 1 to 24.1 mg/L. In addition, chlorpyrifos and permethrin accumulated i n the tissues of juvenile 0. latipes. Observations of five behavioral/ morphological responses, including changes in equilibrium, general act ivity, startle response, and morphology (e.g., hemorrhage and deformit ies) were used as indicators of sublethal toxicity. Each chemical, wit h the exception of 2,4-DNP, elicited a distinct behavior or set of beh avioral responses. The behavioral toxicology bioassay may be valuable in comparing and predicting the mode of action of new or unknown toxic ants in this species of fish.