DEVELOPMENTAL DIFFERENCES IN THE STEROL COMPOSITION OF SOLENOPSIS-INVICTA

Twenty-six sterols were isolated from eggs, larvae, workers, and queen s of the red imported fire ant, Solenopsis invicta Buren. They were id entified by chromatographic (TFC, GLC, and HPLC) and spectral methods (MS and H-1-NMR). Queens possessed the most varied sterol composition (24 sterols were detected). The major sterols from queens were the dou bly bioalkylated 24 alpha-ethyl cholest-5- and 7-en-3 beta-ols whereas the major sterol from the other developmental stages was cholesterol, a sterol which lacks a C-24 alkyl group. From fourth instar larvae we re isolated two yeasts, Candida parapsilosis and Yarrowia lipolytica. Both yeasts were found to synthesize similar sterols, primarily ergost erol and zymosterol (90% of the sterol mixture). A minor sterol (appro ximately 12% of the total sterol mixture) detected in eggs, larvae, an d workers was 24-methyl cholesta-5,22E-dien-3 beta-ol (brassicasterol) . Brassicasterol may have originated from ergosterol produced by the f ungal endosymbiotes. The amount of sterol in each developmental stage was as follows: approximately 24 mu g sterol/queen, 3 mu g sterol/work er, 2 mu g sterol/larvae, and 0.02 mu g sterol/egg. The sterol composi tion of the red imported fire ant differed from that of leaf-cutting a nts previously investigated where 24-methyl sterols of ectosymbiotic f ungal origin were the major sterols detected in soldiers and workers. (C) 1995 Wiley-Liss, Inc.