Abstract
Labyrinthulids are fungoid protists in the kingdom Chromista. In the coastal ecosystem, they are important decomposers. Labyrinthulids produce polyunsaturated fatty acid, docosahexaenoic acid (DHA). The biosynthetic pathway of the DHA has been investigated, but few cytological studies on the DHA biosynthesis have been conducted. We observed lipid bodies stained with Nile Red and found that the cells accumulate lipid bodies during the cell development from the zoospore to the vegetative cell. It is suggested that the electron microscopy using freeze-substitution technique can reveal lipid bodies containing 1,3-dipalmitoyl-2-DHA-triacylglycerol. Using this technique, we found more lipid bodies containing DHA in the vegetative cells than in the zoospores. Analysis of fatty acid content and composition demonstrated that the zoospores contain lower level of fatty acid than those in the vegetative cells. On the other hand, the ratio of DHA in the fatty acid was higher in the zoospores than in the vegetative cells.
