Cell junctions between spermatozoa flagella within the spermatozeugmata of Tubifex tubifex (annelida: Oligochaeta)

The spermatozeugmata (sperm bundles) of Tubifex tubifex consist of an inner cylinder containing “fertilizing” spermatozoa and a cortex composed of helically wound “modified” spermatozoa with degenerated nuclei. Modified flagella are linked together by two types of junctions, one resembling the adherens junction in the cortex periphery, the other septate-like present throughout the major portion of the cortex. The structure and architecture of the septate junctions have been investigated by means of conventional fixation, impregnation techniques, and freeze-fracture studies. A model is presented consisting of rows of “pillars” constituting the septa walls. These are paired to form a series of intercellular “tubules” or channels. The septate junctions are not occluding and a mechanical function is envisaged. Tubule orientation is discussed in connection with spermatozeugma formation.