THE CYTOSKELETON OF THE NAKED GREEN FLAGELLATE SPERMATOZOPSIS-SIMILIS(CHLOROPHYTA) - ANALYSIS OF ISOLATED BASAL APPARATUSES IN THE PARALLEL CONFIGURATION

The biflagellate green alga Spermatozopsis similis is demonstrated to be a model organism for the biochemical and functional analysis of the basal apparatus. Basal apparatuses were isolated in the presence of 1 0(-6) M Ca2+, which induces the reorientation of the basal bodies into the parallel state. Serial thin sectioning of enriched basal apparatu ses stained with tannic acid reveals several novel details of the stru cture of the basal bodies, the distal connecting fiber, and the striat ed microtubule-associated fibers. We observed a pronounced difference in size of a striated fiber connecting the basal bodies to the five-st randed micro-tubular roofs depending on its association with the devel opmentally older or younger basal body. Instead of a proximal connecti ng fiber, the proximal end of each basal body is associated with a str iated triangular plate; these plates appear to serve as spacers for th e basal bodies in the parallel and antiparallel configurations. We sug gest that the plates play a role in maintaining basal body orientation during forward and backward swimming. The results are summarized in r epresentative drawings of the basal apparatus.