Nuclear changes during spermiogenesis in two chrysomelid beetles.

Ultrastructural and cytochemical studies were carried out on sperm nucleus of the beetles, Coelomera lanio and Diabrotica speciosa. Nuclear development involves changes in the shape and in the degree of chromatin condensation, with specific aggregation patterns of DNA-histone complex occurring during this process. Lamellar and paracrystalline arrangements of the nuclear material were observed in the Diabrotica speciosa spermatid and in the Coelomera lanio spermatozoon, respectively. Ethanolic-phosphotungstic acid technique suggest the presence of basic proteins in the nuclear material of spermatids. This reaction disappears during chromatin condensation. Chromatin condensation patterns may reflect specific intranuclear mechanisms and offers protection to the genome during spermatozoon transport to the oocyte.