Spermatozopsis similis basal apparatus tour.

The triangular proximal plates.

The proximal plates contain BAp90. They are massive triangular structures associated with the proximal end of each basal body. They form stable spacers between the basal bodies preventing them from sliding past each other under the forces of flagellar motility and basal body reorientation. Antiparallel orientation of the basal bodies: Two consecutive transverse sections (A, B) through a basal apparatus with antiparallel orientation of the basal bodies. The proximal plates (arrowheads) are located on the top of each other. Parallel orientation of the basal bodies: Transverse section trough the proximal end of a basal apparatus with parallel orientation of the basal bodies. The proximal plates (arrowheads) lie side by side in the same plane.