Production of amphisterol and other Δ8(14) sterols by Togula jolla (formerly Amphidinium sensu lato) overlaps chemotaxonomically with Amphidinium carterae

Abstract

While a longstanding method for identifying dinoflagellates, morphology alone can be inaccurate because of convergent evolution of truly different species toward a particular cellular shape. The dinoflagellate genus Togula is a case in point in that its type species Togula britannica was previously assigned to the genus Amphidinium based on morphology but was recently recognized as an independent genus following phylogenetic characterization. Chemotaxonomy can be a useful tool to complement the characterization of dinoflagellates by phylogeny. To this point, some, but not all, species of Amphidinium, such as Amphidinium carterae, have been observed to produce the rare 4α-methyl-substituted, Δ⁸⁽¹⁴⁾-nuclear-unsaturated major sterol 4α-methyl-5α-ergosta-8(14),24(28)-dien-3β-ol (amphisterol) that has historically been considered a potential chemotaxonomic biomarker for the genus as it is found in very few other dinoflagellate genera. To date, no isolates within the genus Togula have had their sterols characterized; our objective was thus to provide a first examination of the sterols of an isolate of Togula to compare to the sterols of Amphidinium. To this end, we have characterized the sterols of Togula jolla, one of the few members of Togula available for study, to demonstrate the production of amphisterol, among other Δ⁸⁽¹⁴⁾-nuclear unsaturated sterols, as its major sterol.