Sterol composition and the classification of the demospongiae

The Demospongiae (Porifera) have yielded a wide range of novel and conventional sterols; a sample of 55 species screened and reported on have yielded 45 distinct sterol structures. The taxonomic relevance of the occurrence of particular sterols or overall sterol complement is evaluated and has proved to be informative in the case of the Verongida, Nepheliospongida, Axinellida and Hadromerida. A possible relationship between the occurrence of 26-methyl sterols and oviparous reproductive patterns within the Ceractinomorpha is noted. Sterol complement is observed to be qualitatively stable despite season and location of collection. High molecular weight sterols, present as major components, are probable membrane constituents. They afford an interesting parallel to the occurrence of diverse, high carbon fatty acids in sponge membranes.