Accumulation of chlorine-36 ring-labeled DDT residues in various tissues of two species of shrew

Abstract

Storage of DDT [trichloro-bis-(p-chlorophenyl) ethane] residues by the shrew species,Blarina brevicauda andSorex cinereus, was studied in a 4.05-hectare old-field ecosystem, treated in June, 1969, with³⁶Cl-ring-labeled DDT at a dosage of 0.92 kilograms per hectare. The mean radioactive DDT-derived residue contents ofBlarina liver (10 ppm), muscle (10 ppm), brain (4 ppm), and fat (135 ppm) of resident shrews were the same in 1970 and 1971, and they were not influenced by sex. Significant peaks occurred in the DDT residue content of fat in August, 1970 (243 ppm) and November, 1971 (236 ppm), which may have resulted from the consumption of slugs (Deroceras), whose population peaks coincided with the maximum residue levels of DDT in fat.Blarina released into the treated area accumulate DDT-derived residues in liver, brain, muscle, and fat comparable to the levels found in resident shrews, within 15 to 20 days of exposure to the area. Equilibrium between intake and excretion of DDT apparently occurs inBlarina liver, brain, and muscle within approximately 30 days and, in fat, within 40 days. InSorex, DDT residue levels in muscle and viscera reached peaks during the summer of DDT application (1969) and declined towards the end of the growing season, the pattern being similar to that found for the tissues ofBlarina. However,Sorex, unlikeBlarina, accumulated residue levels of DDT in 1970 and 1971 which were successively greater than the levels present in 1969, indicating that DDT probably was increasing in availability toSorex, with the passage of time. Mean levels of DDT residue in muscle (4 ppm) and viscera (3 ppm) are not influenced by sex but are influenced by breeding condition. Male shrews with scrotal testes and lactating females develop lower levels of DDT in muscle and viscera than males with abdominal testes or nonlactating females.