Neutral sterols of representatives of two groups of hemiptera and their correlation to ecdysteroid content

Abstract

AbstractThe sterols of four species of Pentatomomorpha—Oncopeltus fasciatus (Dallas), Nezara viridula (L.), Dysdercus cingulatus (F.), and Podisus maculiventris (Say)—and threé species of Cimicomorpha—Rhodnius prolixus Stal, Arilus cristatus (L), and Cimex lectularius (L.)—were isolated and examined in order to compare neutral sterol utilization and content with the known ecdysteroids of these species. In the phytophagous Pentatomomorpha, O. fasciatus, N. viridula, and D. cingulatus, the low content of cholesterol and the high content of C28 and C29 phytosterols (< 1% and > 99% of the tissue sterols, respectively) indicated that these species are unable to dealkylate the C‐24 position of sterols. These insects appear to have adapted to the challenge of both insufficient dietary cholesterol and inability to dealkylate phytosterols by evolving the ability to produce a C28 ecdysteroid (makisterone A). The secondarily predacious P. maculiventris has adequate cholesterol available for C27 ecdysteroid production, but appears to have retained the ecdysteroid biosynthetic pathways of its phytophagous ancestors because it produces a C28 ecdysteroid. Cholesterol was the major sterol of each of the three species of Cimicomorpha, and these insects are only able to produce C27 ecdysteroids.