Effects of lead-contaminated sediment and nutrition on mallard duckling brain growth and biochemistry.

Day-old mallard (Anas platyryhnchos) ducklings received either a clean sediment (24%) supplemented control diet, Coeur d'Alene River Basin, Idaho (CDARB) sediment (3449 microg/g lead) supplemented diets at 12% or 24%, or a positive control diet (24% clean sediment with equivalent lead acetate to the 24% CDARB diet) for 6 weeks. The 12% CDARB diet resulted in a geometric mean concentration of 396 ppb (WW) brain lead with decreased brain protein and ATP concentrations but increased oxidized glutathione (GSSG) relative to the control diet. The 24% CDARB diet resulted in a concentration of 485 ppb brain lead with lower brain weight and ATP concentration than controls but higher concentrations of reduced glutathione (GSH) and calcium. Lead acetate accumulated twice as well as CDARB derived lead and resulted in histopathological lesions of the brain. With a combination of a suboptimal diet and 24% CDARB, brain lead concentration was higher (594 ppb) than with 24% CDARB in the standard diet, histopathological lesions became apparent and GSH was higher than suboptimal diet controls.

Effects of diquat, an aquatic herbicide, on the development of mallard embryos.

Bipyridylium herbicides produce embryotoxic and teratogenic effects in dipteran, amphibian, avian, and mammalian organisms. Diquat dibromide, a bipyridylium compound, is commonly used as an aquatic herbicide. Mallard (Anas platyrhynchos) eggs were exposed to diquat by immersing the eggs for 10 s in solutions of 0.88, 3.5, 7, 14, or 56 g/L on either d 4 or 21 of incubation. Application of diquat on d 4 yielded an estimated LC50 of 19.5 g/L through 18 d of incubation, and 9.6 g/L through hatching. Body and organ weights, and bone lengths of hatchlings did not differ between control and treatment groups with the exception of a slight increase in brain weight in the 14 g/L group. Malformations in diquat-treated embryos included defects of the brain, eye, bill, limb, and pelvis; skeletal scoliosis; and incomplete ossification. Subcutaneous edema was also present. Significant manifestations of oxidative stress were apparent in hatchlings and included increased hepatic thiobarbituric acid-reactive substances (TBARS) (lipid peroxidation) and decreased brain reduced glutathione (GSH). Brain protein-bound sulfhydryls (PBSH) increased. Diquat applied on d 21 of incubation yielded an estimated LC50 of 12.6 g/L through hatching. Exposure at this late stage of development did not produce deformities. Body and organ weights and, bone lengths of hatchlings did not differ between control and treatment groups. Significant manifestations of oxidative stress in hatchlings included decreased brain GSH, increased oxidized glutathione (GSSG), and ratio of GSSG to GSH. This study suggests that concentrations of diquat commonly used for aquatic weed control, when based upon the dilution effect of average water depth of the application area, would probably have little impact on mallard embryos. However, concentrations applied above ground to weeds and cattails along ditches could adversely affect the survival and development of mallard embryos, and presumably other avian species nesting in such habitats.