Methyl mercury induced visual deficits in rainbow trout

Abstract

Scotopic spectral sensitivity of 15 rainbow trout was determined using a two-choice, operant-conditioning task. Maximum sensitivity occurred at 525 nm and generally declined at longer and shorter wavelengths with evidence of a "shoulder" at 600–650 nm. Fifteen days after injection with either saline control (n = 4) or 4.6–6.2 mg of methyl mercury chloride per kilogram of body weight (n = 9); measurements of response latency and trials to criterion revealed that methyl mercury (MEHG) did not affect memory or motor performance. MEHG did produce significant spectrally uniform decrements in visual sensitivity. These results suggest that MEHG impaired both the scotopic and photopic mechanisms of MEHG-treated rainbow trout.