part of axial complex fly_anatomy.ontology FBbt:00004949 The complex formed by the axoneme and Nebenkern derivatives that extends the length of the sperm tail at the end of the elongation stage. The position between the axoneme and the Nebenkern derivatives is characteristic, although they become somewhat independent regarding rotation after the sperm bundle coils during individualization stage. elongation stage spermatid individualization stage spermatid cell component male-specific anatomical entity