Analysis of the nucleolar organizing regions in the ant Tapinoma nigerrimum (Hymenoptera, Formicidae)

This study analyses the NORs of Tapinoma nigerrimum, a species that, as known from previous studies, has various chromosomes which carry a NOR site. The analysis was made by a combination of three methods: silver nitrate staining, in situ hybridization with fluorescein- or digoxigenin-labelled probes, and staining with the CG-specific fluorochrome chromomycin A3. The silver staining technique showed an Ag-positive region on chromosome 6 and on various other chromosomes. However, the application of in situ hybridization techniques showed only one positive signal in the proximal region of the short arm of chromosome 6 of T. nigerrimum. Similar results were observed by CMA banding. The absence of rDNA genes or the presence of only a small number of these, not detectable with the above probes, might explain the absence of hybridization signal in the remaining chromosomes.