SURVIVAL AND GROWTH OF JAPANESE MEDAKA (ORYZIAS LATIPES) EXPOSED TO TRICHLORETHYLENE AT MULTIPLE LIFE STAGES: IMPLICATIONS OF ESTABLISHING THE MAXIMUM TOLERATED DOSE FOR CHRONIC AQUATIC CARCINOGENICITY BIOASSAYS

Abstract

To evaluate the most sensitive life stage of the Japanese medaka (Oryzias latipes) at which to determine the maximum tolerated dose for chronic carcinogenicity bioassays, the effects of trichloroethylene (TCE) on growth and survival of the medaka were examined at several life stages. A series of 7-day flow-through exposures was conducted with medaka at 4, 7, 10, 13, 16, 28, 42, and approximately 180 days posthatch. Growth, measured as standard length and area, was more sensitive than survival in fish that were 4 to 13 days old at the start of the tests. Medaka 7, 10, and 13 days posthatch established the lowest observed effect concentration for all life stages, based on growth at 8.8 to 10.1 mg/L. There were no significant effects on growth of fish more than 16 days old at the study's initiation. Values of lethal concentration to 50% of the test organism calculated for the various life stages ranged from 23.0 mg/L for 16-day-old fry to 37.0 mg/L for 4-day-old fry. Survival was most affected by TCE in fish more than 10 days old at the initiation of exposure. The sensitivity of the medaka to TCE, as determined by both survival and growth, changed with age. Growth is a sensitive indicator of adverse effect and can be accurately evaluated in as few as 7 days; according to the data presented here, it is best demonstrated in medaka 13 days or fewer posthatch.

Keywords: :

• Dose Growth Medaka Survival Trichloroethylene