Origin and development of free kinetosomes in the flagellates Deltotrichonympha and Koruga

The formation of more than half a million free (non-flagellated) kinetosomes in post-mitotic Deltotrichonympha and Koruga from Mastotermes is described. Ladder-like configurations of prokinetosomes extend from the 2 fibrous walls of the centriolar apparatus in the rostrum. The prokinetosomes within the ladders are arranged side by side in 2 layers. Because the fibrous walls are oriented perpendicular to each other, the 2 groups of prokinetosomal ladders are also mutually perpendicular. The prokinetosomes arise continuously next to the fibrous walls, and migrate outward along the ladders as they develop. Consequently, progressive stages in kinetosome formation occur sequentially along the ladders in a polarized fashion. A cartwheel-structure appears first. This is followed by the formation of A tubules, B tubules and C tubules in an orderly sequence around the cartwheel (counter-clockwise, viewed from the distal end). The cartwheel ring disappears after the triplets have formed. The new free kinetosomes accumulate in a disorganized mass at the ends of the ladders. Later, the kinetosomes become organized end to end into the polarized chains found in interphase cells. The fibrous wall of the centriolar apparatus is thus a new type of intermediate structure associated with the mass production of basal bodies. It appears to determine the spatial organization of the 'assembly lines' of developing kinetosomes.