. Bulletin. Natural history; Natural history. 414 Illinois Natural History Survey Bulletin Vol. 30, Art. 6 Toble 5. â Uptake of '*C-DDT and ^H-methoxychlor in a daphnia-to-guppy food chain. Insecticide Concentration^ in Daphnia in ppm Days Fish Fed on Daphnia Exposed to Insecticide Insecticide Concentration" in Fish in ppm Rate of Insecticide Uptake From Food By Fish ppm in Fish ppm in Daphnia Ratio of Rates of Uptake by Fish, DDT to Methoxychlor Methoxychlor DDT 20 20 "All
. Bulletin. Natural history; Natural history. 414 Illinois Natural History Survey Bulletin Vol. 30, Art. 6 Toble 5. â Uptake of '*C-DDT and ^H-methoxychlor in a daphnia-to-guppy food chain. Insecticide Concentration^ in Daphnia in ppm Days Fish Fed on Daphnia Exposed to Insecticide Insecticide Concentration" in Fish in ppm Rate of Insecticide Uptake From Food By Fish ppm in Fish ppm in Daphnia Ratio of Rates of Uptake by Fish, DDT to Methoxychlor Methoxychlor DDT 20 20 "All such concentrations were calculated on a dry-weight basis. and Fig. 5. There was little difference in the uptake of the two insecticides from water by the daphnia. However, when the daphnia entered the food chain, the methoxychlor content in the 10-> ? 8- 6- 4- 2- â DDT ⢠METHOXYCHLOR. 10 20 EXPOSURE TIME (DAYS) Fig. 5. â Uptake of "C-DDT and ^H-methoxy- chlor by guppies in a daphnia-to-guppy food choin. The dophnio were held in wafer containing 0,003 ppm of DDT or methoxychlor for 48 hours before being fed to the fish. fish rapidly reached a steady state, while the concentration of DDT con- tinued to increase. From the 6th to the 20th day the methoxychlor level in the guppies increased only from to ppm, but the DDT level increased from to ppm. The differences in concentration of the two compounds are shown by the relative values of the rates of uptake by the fish from the daphnia (column 4 of Table 5) and by the ratios of the rates of uptake (col- umn 5). The difference in accumula- tion is due to the presence of alkoxy groups on the aryl rings in methoxy- chlor, which cause it, unlike DDT, to be subject to attack by multifunction oxidases of the fish and, therefore, to be rapidly metabolized and excreted. In general, our investigations show that methoxychlor appears to be read- ily biodegradable in fishes and in some, though not all, other aq
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