Ultrastructure and Lipid Composition of Zooxanthellae from Tridacna maxima

Abstract

Isolation of zooxanthellae (Gymnodinium microadriaticum) from clam tissue does not result in any loss of the outer limiting layers and the ultrastructure of the cell is similar to that of zooxanthellae found in other clams and corals. The major lipid components of G. microadriaticum are galactosyldiacylglycerols which comprise about 50% of the extractable lipid. The major fatty acids present are palmitic, γ-linolenic and octadecatetraenoic acids, together with a component identified as octadecapentaenoic acid. The presence of γ-linolenic acid is more representative of animal lipids than of plant lipids and there is a possibility that growth of the zooxanthella in a host tissue can affect the fatty acid composition.