Changes in the nuclear envelope associated with spermatid differentiation in the shrimp, Crangon septemspinosa

The nuclear envelope during the sequential steps of spermiogenesis in the shrimp, Crangon septemspinosa, was followed by electron microscopy of thin-section and freeze-fracture preparations. Localized modifications of the nuclear envelope were observed which are consistent features, identifiable and unique to particular regions of this intact membrane system at specific stages during spermatid differentiation and in the mature sperm. The observed changes include: reduction of perinuclear space caused by apposition of nuclear membranes, perinculear extensions of the outer nuclear membrane, change in shape and reduction in size of the nucleus, establishment of nuclear pore-rich and nuclear pore-deprived zones, and clustering of nuclear pores and their increased diameters in mature sperm. From these structural changes, the nuclear envelope is viewed as a dynamic membrane interface whose structural modifications are correlated with changes of the nucleus and the cytoplasm.