Nuclear Shaping in the Absence of Microtubules in Scorpion Spermatids

During spermiogenesis in most animal species, sperm nuclei undergo morphogenesis which results in the transformation of relatively large spherical nuclei with diffuse chromatin into small elongate or flattened nuclei with highly condensed chromatin. The shapes of nuclei of mature spermatozoa are beutifully precise and species-specific. There is no general agreement among cell biologists as to the forces which effect nuclear shaping. Some investigators have suggested that microtubules which surround spermatid nuclei during shaping play an active role in this process (Mclntosh and Porter, 1967; Kessel, 1966, 1970), whereas others have suggested that nuclear condensation is effected by internal condensation of chromatin (Fawcett et al., 1971). It has also been suggested that nuclear condensation and shaping could result from the interplay of nucleus, cytoplasmic organelles, and supportive cells (Phillips, 1970; Rattner, 1972). In this report, I shall describe nuclear shaping during spermiogenesis in two species of scorpion where the formation of a highly compacted sperm nucleus from a large spherical nucleus appears to be effected without interaction with microtubules.