Uptake of 36Cl-DDT residues by slugs and isopods in the laboratory and field

Slugs Lehmannia valentiana and isopods Tracheoniscus rathkei exposed to contaminated turf from a pasture treated 4 years previously with 36Cl-DDT, accumulated maximum body burdens of DDT residues in 55 days under glasshouse conditions; in outdoor enclosures, uptake was hindered by lack of rainfall and low temperatures. In the glasshouse, slugs maintained an equilibrium level of 14.0 ppm from 55 to 80 days, whereas isopods attained a peak of 22.5 ppm, after which residues declined over the next 20 days to 14.8 ppm. In the enclosures, residues reached 20.3 ppm in isopods, but never exceeded 5.0 ppm in slugs. Slugs were more adversely affected by low moisture, but less affected by cold than were isopods. Minimal uptake of residues by L. valentiana from contaminated vegetation and detritus, in the absence of soil, indicated that soil was a more important source of residues than food. (author)