PINGUIOPHYCEAE

The Pinguiophyceae is a class of marine planktonic algae that were previously classed as “chrysophytes.” Analysis of nuclear-encoded 18S rRNA and chloroplast-encoded rbcL gene sequences uncovered the close relationship of the organisms in this class (Kawachi et al., 2002). The class is characterized by unusually high concentrations of polyunsaturated acids, especially 20:5 (n-3) (EPA-eicosapentaenoic acid) in the cells (Kawachi et al., 1996) (Fig. 13.1). These fatty acids are the basis for choosing the latin noun “Pingue” (meaning fat, grease) as the root of the class name. The high percentage of unsaturated fatty acids, and the lack of a cell wall, make these algae desirable as a source of unsaturated fatty acids and of animal feed.

The cells (Figs. 13.2, 13.3) (Honda and Inouye, 2002) are derived from a typical heterokont ancestor with an anterior tinsel flagellum with tripartite hairs and a posterior smooth whiplash flagellum (although many of the genera have lost one or both flagella through evolution). The chloroplasts have two membranes of chloroplast endoplasmic reticulum, the outer membrane continuous with the nuclear envelope. A girdle band of thylakoids occurs under the chloroplast envelope. Pyrenoids occur in the chloroplast and the mitochondria have tubular cristae. Chlorophyll a and chlorophyll c-related pigments as well as fucoxanthin, violaxanthin, zeaxanthin, and β-carotene are present.