ACUTE AND LONG-TERM EFFECTS OF 9 CHEMICALS ON THE JAPANESE MEDAKA (ORYZIAS-LATIPES)

Ninety-six-hour acute and 28-day larval survival and growth tests were conducted with nine organic chemicals, using the Japanese medaka (Ory zias latipes) as the test organism. The nine tested chemicals were all yl isothiocyanate, aniline, benzyl acetate, 4-chloroaniline, 2-chloroe thanol, 2,4-diaminotoluene, 1,2-dibromoethane, 2,4-dichlorophenoxyacet ic acid (2,4-D), and phenol. The derived 96-h LC50 values for medaka f or all chemicals ranged from 0.077 mg/L for allyl isothiocyanate to 2, 780 mg/L for 2,4-D. The chronic values for six of the nine chemicals t ested ranged from 0.013 mg/L for allyl isothiocyanate to 42.5 mg/L for 2,4-D. Acute-to-chronic ratios for these six chemicals ranged from 1. 4 for 2-chloroethanol to 70.9 for 2,4-D. Growth of medaka was signific antly reduced in the lowest exposure concentration during 28-day larva l tests with aniline, 4-chloroaniline, and 2,4-diaminotoluene. The est imated maximum acceptable toxicant concentration was reported as less than the lowest exposure concentration of 4.6, 2.2 and 40.3 mg/L for t ests with aniline, 4-chloroaniline and 2,4-diaminotoluene, respectivel y. Chronic values for 2-chloroethanol and medaka were 12.6 mg/L during an embryo-larval test and 22.1 mg/L during the 28-day larval test.