Cardiac glycosides in Oncopeltus fasciatus (Dallas) (Hemiptera: Lygaeidae). I. The uptake and distribution of natural cardenolides in the body

Abstract

Oncopeltus fasciatus sequesters cardiac glycosides from seeds of Asclepias syriaca, and in the adult, concentrates these chemicals in the dorsolateral spaces of the thorax and abdomen; 60 to 95% of the cardenolide in such adults is stored in the dorsolateral complex. Very little cardenolide is detectable in the haemolymph of adults and larvae, but cardiac glycosides do occur in the adult ventral metathoracic gland secretions and in the larval middorsal abdominal gland fluid.O. fasciatus sequesters cardenolides throughout its life cycle. The complement of cardenolides acquired by feeding throughout the development is not related simply to increase in body weight. Unknown factors during late larval development are important in the accumulative uptake of the heart poisons.It is shown that O. fasciatus sequesters polar but not non-polar cardenolides into the dorsolateral complex in the adult. The accumulation of the polar cardenolides in both the larva and adult appears to be, at least in part, associated with the ability of the insect to metabolize heart poisons. The non-polar cardenolide digitoxin was converted to at least two more polar cardenolides. Adult O. fasciatus did not, however, metabolically alter the chromatographic behavior of ouabain that had been added to the food.