Variations with age in the adrenocortical responses of mallard ducks (Anas platyrhynchos) consuming petroleum-contaminated food.

Abstract

Mallard ducks were fed ad libitum a diet containing 3 ml South Louisiana crude oil per 100 gm dry food. Plasma samples were analyzed for corticosterone by radioimmunoassay and hepatic mixed function oxidase activity was determined in microsomal fractions from liver homogenates. Results show that birds in each age group, whether consuming either uncontaminated or contaminated food, showed no significant changes in body weight during the ten-day experimental period. Also, no significant differences were detected between the rates of food consumption by birds in the various age groups. The similar levels of total hepatic mixed function oxidase activity induced by the similar volumes of crude oil consumed by the individuals in each age class strongly suggests that the declines inplasma corticosterone concentration occurred in response to similar levels of systemic contamination. Since the decreases were larger in the younger birds than in the older birds, age seems to have been an important factor determining the degree of hypoadrenocorticalism developed following their exposure to contaminated food. (JMT)