ANALYSIS OF THE NUCLEOLAR ORGANIZING REGIONS IN THE ANT TAPINOMA-NIGERRIMUM (HYMENOPTERA, FORMICIDAE)

This study analyses the NORs of Tapinoma nigerrimum, a species that, a s known from previous studies, has various chromosomes which carry a N OR site. The analysis was made by a combination of three methods: silv er nitrate staining, in situ hybridization with fluorescein- or digoxi genin-labelled probes, and staining with the CG-specific fluorochrome chromomycin A(3). 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 positi ve signal in the proximal region of the short arm of chromosome 6 of T . nigerrimum. Similar results were observed by CMA banding. The absenc e of rDNA genes or the presence of only a small number of these, not d etectable with the above probes, might explain the absence of hybridiz ation signal in the remaining chromosomes.