A TEST OF THE EQUIPOTENCY OF INTERNAL BURDENS OF 9 NARCOTIC CHEMICALS USING DAPHNIA-MAGNA

The hypothesis of constancy of the tissue residues in animals succumbed to narcotic organic chemicals is tested by determining the effect of bodylength, time, and ambient concentration on tissue concentration in Daphnia magna narcotized by exposure to toxic levels of nine C-14-labeled, narcotic organic compounds: acetone, acetophenone, benzene, butanol, 1,2-dichlorobenzene, 2-methylnaphthalene, 1,1,2,2-tetrachloroethane, 1,2,4-trichlorobenzene, and toluene. The average tissue concentration of immobilized D. magna was 3.1 mmol/kg (95 % confidence limits = 1.1-5.1 mmol/kg), but ranged from 0.15 mmol/kg for 2-methylnaphthalene to 200 mmol/kg for butanol. When all chemicals are pooled in analysis, time (seconds to days) had no effect on the effective tissue concentrations of narcotics, body size (0.4-3 mm) had a small but significant effect, and ambient concentrations (1/10th to 48-h LC50) had the strongest effect. When the chemicals were analyzed separately, the influence of duration of exposure, body size, and ambient concentration varied.