Twenty-six sterols were isolated from eggs, larvae, workers, and queens of the red imported fire ant, Solenopsis invicta Buren. They were identified by chromatographic (TLC, GLC, and HPLC) and spectral methods (MS and 'H-NMR).Queens possessed the most varied sterol composition (24 sterols were detected). The major sterols from queens were the douhly bioalkylated 24a-ethyl cholest-5-and 7-en-3P-01~ whereas the major sterol from the other developmental stages was cholesterol, a sterol which lacks a C-24 alkyl group. From fourth instar larvae were isolated two yeasts, Candida parapsilosis and Yarrowia lipolytica.Both yeasts were found to synthesize similar sterols, primarily ergosterol and zymosterol (90% of the sterol mixture). A minor sterol (approximately 12% of the total sterol mixture) detected in eggs, larvae, and workers was 24-methyl cholesta-5,22E-dien-3~-ol (brassicasterol). Brassicasterol may have originated from ergosterol produced by the fungal endosymbiotes. The amount of sterol in each developmental stage was as follows: approximately 24 pg steroI/queen, 3 pg sterol/worker, 2 pg sterol/larvae, and 0.02 pg sterol/egg. The sterol composition of the red imported fire ant differed from that of leaf-cutting ants previously investigated where 24-methyl sterols of ectosymbiotic fungal origin were the major sterols detected in soldiers and workers. o 1995 Wile\,-Liss, Inc.

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The problem of blue-green algal toxin contamination of recreational waters and drinking water catchments is well described, as is the potential contamination of associated seafood. Algal contamination of Victorian waterways is now a widespread annual occurrence and, in some regions, the intersection of blooms and commercial fishing threatens the food safety of large numbers of people. Toxin levels which produce no observed adverse effect in animal studies were used to derive safe tolerable daily intake levels. These 'acceptable levels' were then modified to protect against potential acute health risks associated with short-term exposures. National food surveys were used to derive likely seafood intakes and thus, in combination with 'safe toxin levels', health alert levels for seafood were formulated. During the summer of 2001 a bloom of Nodularia spumigena occurred in the Gippsland Lakes area of Southern Victoria. During the bloom, seafood samples were collected and nodularin concentrations were estimated. Nodularin concentrations reached levels of concern in mussels and in prawn viscera at cell counts as low as 30,000 cells/ml. Nodularin concentrations in the flesh of finfish remained low. Boiling the seafood redistributed toxin between viscera and flesh. The results were used to restrict some seafood harvesting.