Organization and Fine Structure of the Side Body and Its Lipid Sac in the Zoospore of Blastocladiella Emersonii

SUMMARY

Analyses of serial sections have shown that the “lipid sac” in the zoospore of Blastocladiella emersonii is made up of three detectable components. One is an irregularly edged, spoon bowl-shaped cup delimited by a unit membrane. This cup, in effect, is a continuous matrix of varying thickness in which lipid granules (the second component) are partially embedded. A retaining sheet of two parallel unit membranes, the third component, lies along the outside of the matrix, holding it closely appressed against the spore's single mitochondrion. The two members of this backing membrane connect at several points to the outer unit membrane of the nuclear cap. In the region where it is positioned against the cup-shaped matrix, the backing membrane is visibly differentiated such that the space between its two unit membranes appears electron-dense. The relationship of the “lipid sac” to other organelles in the posterior region of the zoospore is evaluated in the light of these and other observations.