Effects of Sublethal DDT on a Simple Reflex in Brook Trout

Brook trout were conditioned in about 30 trials to exhibit the propeller-tail reflex, with electric shock as the unconditioned stimulus and light as the conditioning stimulus. When the trout were exposed for 24 hr to sublethal DDT (20 ppb), more than half could not be conditioned at all; the remainder required significantly more trials than did the untreated ones. Three to four weeks after initial testing, the DDT effect had largely disappeared. It seemed likely that the DDT was acting upon central nervous system structures. The general ecological implications of the results are discussed.