Anreicherung,verteilung, umwandlung und ausscheidung von DDT-14C bei Solea solea (Pisces: Soleidae)

Common soles Solea solea (L.) are extremely suitable for studying the fate of pesticides in marine fish by means of laboratory experiments involving small-sized, accurately controlled, closed aquarium systems. In 5 different experiments, a total of 16 fishes of Age Group I were maintained in water of 10°C and 20‰ S continuously filtered through charcoal, and given oral doses of 0.85 μg DDT-¹⁴C up to 5 times/week. A total application of 1.7, 17 or 35 μg DDT-¹⁴C, corresponding to 3, 28, or 57 experimental days, resulted in 72, 60 or 43% DDT-¹⁴C accumulation. After feeding with 17 μg unlabelled DDT over a period of 4 weeks and final feeding with 1.7 μg ¹⁴C-labelled DDT for 2 days, S. solea displayed the same percentage (74%) of accumulated DDT-¹⁴C as after feeding with 1.7 μg DDT-¹⁴C without prior feeding. Therefore, the decreasing accumulation percentages with inereasing doses, i.e., with longer application periods, are due to elimination during the application period. During a period of 2 months in pesticide-free water, S. solea eliminated 62% of the DDT-¹⁴C which it had accumulated after feeding with 17 μg DDT-¹⁴C over a period of 4 weeks. The gastro-intestinal tract is assumed to be a major route of DDT elimination. Independent of dosage, there was a characteristic distribution pattern of accumulated DDT: brain, liver and gastro-intestinal tract ranked highest, while the concentration in skeletal muscle was lowest. Even during the elimination period the pattern appeared unchanged. DDE, DDD and a polar component occurred as metabolites, but in all organs more than 80% of the accumulated DDT remained unchanged. Percentages of metabolites were higher in liver and gastro-intestinal tract than in skeletal muscle. Prolonged exposure to DDT in the diet induced DDT transformation in the gastro-intestinal contents, most probably in the bacterial flora of the gut.