Pattern of nucleolar organizer region activity during male meiosis in Callicrania seoanei (Orthoptera) as analyzed by silver staining: evidences for a possible reactivation in the period between the two meiotic divisions

Silver staining of spermatocytes and early spermatid nuclei from the neo XY race of the Tettigonioid species Callicrania seoanei reveals an active nucleolar organizer region (NOR) located proximally in a medium-sized bivalent. Ag-positive material was present at the NOR in all stages of male meiosis. However, the results obtained indicate that transcriptional activity of ribosomal cistrons (rDNA) is not maintained throughout spermatogenesis, but that NOR reactivation might occur in the period between the two meiotic divisions in addition to the more general postmeiotical reactivation in the early spermatid nuclei.