Biosynthetic studies of marine lipids 16. De novo sterol biosynthesis in sponges. Incorporation and transformation of cycloartenol and lanosterol into unconventional sterols of marine and freshwater sponges

Cycloartenol and lanosterol, the sterol precursors of photosynthetic and nonphotosynthetic organisms respectively, were transfromed into the 4,4,14-demethyl sterols in most but not all, of a variety of marine and freshwater sponges. Symbiotic cyanobacteria found in many sponges are apparently not involved in the observed biosynthesis. We conclude that while some sponges obtain sterols from the diet, the majority synthesize them de novo.