Structural Analysis and Cellular Localization of Polyunsaturated C27 Hydrocarbons in the Marine Dinoflagellate, Pyrocystis lunula (Dinophyceae)

A neutral lipid fraction obtained from two strains of the permanently sheathed dinoflagellate, Pyrocystis lunula, was found to contain three polyunsaturated C27 hydrocarbons as abundant lipid components. A combination of mass spectrometry techniques was used to identify these compounds as n-heptacosa-3,6,9,12,15,18-hexaene (C27:6, approx. 0.7 ng/sheathed cell), n-heptacosa-3,6,9,12,15,18,21-heptaene (C27:7, approx. 2 ng/sheathed cell), and n-heptacosa-3,6,9,12,15,18,21,24-octaene (C27:8, approx. 2 ng/sheathed cell). Polyunsaturated C21, C23, and C25 hydrocarbons were also found at lesser amounts of approximately 0.2-0.5 ng/sheathed cell. Fluorescent microscopy revealed Nile red staining in both the vegetative cell and structures within the outer sheath surrounding the cell. These hydrocarbons were not present in two other species of Pyrocystis, P. fusiformis and P. noctiluca. Although their function(s) is not known, previous studies have shown and hypothesized that similar hydrocarbons function in carbon storage, buoyancy regulation, or signaling.