Ultrastructure of Spermatozoa and Spermiogenesis in Notonecta triguttata (Hemiptera)

Spermiogenesis in Notonecta triguttata was examined by electron microscopy. The differentiation of the nucleus is described in connection with the enormous reduction of nuclear volume. Four methods can be proposed by which spermatids reduce their nuclear volume. These include 1) formation of pseudochromosomes and nuclear calottes 2) extrusion of nuclear vacuoles and envelope to cytoplasm and to the outside of plasma membrane 3) folding and budding of nuclear envelope into the nucleus 4) condensation of chromatin. During spermiogenesis the microtubules may transport material related to chromatin condensation to the nucleus. Notonecta spermatozoa have well-developed centriole adjunct. This characteristic may be considered as synapomorphy in Nepomorpha.