Long chain (n-c37-c39) alkenones in the prymnesiophyceae. distribution of alkenones and other lipids and their taxonomic significance

Abstract

Long chain (C,37- CV39) n-alkenones, esters of polyunsaturated n-C36acids and C27-C29sterols have been examined in thirteen species from nine genera of algae from the class Prymnesiophyceae and appear to have chemotaxonomic value. The alkenones and esters have been shown to occur in Chrysotila lamellosa and three species of Isochrysis and their presence in Emiliania huxleyi has been confirmed. They were absent from five other members of the order Isochrysidales, and from those representatives of the orders Coccosphaerales, Prymnesiales and Pavlovales examined. This discrimination was reflected in the distribution of the sterols; all five of the above-named species having high concentrations of 24-methylcholcsta-5,22E-dien-3˜-ol relative to cholest-5-en-3˜-ol (cholesterol). In contrast, the former sterol is a minor component in, or is absent from, members of the Prymnesiales and Pavlovales. The sterol distributions suggest that some species at present included in the Isochrysidales (e.g. Ochrosphaera) have closer affinities with species of the Prymnesiales. The Isochrysidales is therefore not a natural taxonomic unit. Pavlova lutheri has sterols and fatty acids in common with members of the Isochrysidales and Prymnesiales, suggesting that the Pavlovales are a relatively ancient group within the Prymnesiophyceae. The distribution of hydrocarbons, fatty acids and carotenoids within the class can provide additional information of taxonomic value in isolated instances. © 1984 British Phycological Society.