Long chain (n-C37–C39) alkenones in the Prymnesiophyceae. Distribution of alkenones and other lipids and their taxonomic significance

Abstract

Long chain (C37-C39) n-alkenones, esters of polyunsaturated n-C36 acids and C27-C29 sterols were examined in 13 spp. from 9 genera of algae from the class Prymnesiophyceae and apparently have chemotaxonomic value. The alkenones and esters occur in Chrysotila lamellosa and 3 spp. of Isochrysis; their presence in Emiliania huxleyi was confirmed. They were absent from 5 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 5 of the above species having high concentrations of 24-methylcholesta-5,22E-dien-3.beta.-ol relative to cholest-5-en-3.beta.-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.