develops from spermatid onion stage spermatid fly_anatomy.ontology A round spermatid containing a spherical Nebenkern with an onion-like arrangement of mitochondrial material. The axoneme begins to grow out from the basal body inserted at the base of the nucleus and the Golgi complexes have fused to form the acroblast and acrosomal granule located at the apical side of the nucleus, opposite the basal body. There is a prominent protein body in the nucleus. FBbt:00004945 clew stage spermatid