The silver impregnation technique located the NOR by staining the proteins present
in this region. Sumner (1990) reported that this method was used to visualize heterochromatic regions that were not associated with NORs in various organisms. Therefore, this suggested that the proteins associated with the NORs were qualitatively similar to those encountered in the heterochromatic blocks of M. segmentaria. Our results
raised issues about the entire effectiveness of Ag-NOR staining, to correctly identify
the NOR in all taxa. Future studies, using specific probes for NORs, by means of the fluorescence in situ hybridization (FISH) technique, might help to elucidate this.
This study is the first detailed karyotype characterization of the Melitoma species, bringing to light several chromosome features, such as, chromosome number, morphology,
heterochromatin pattern, and base pair richness. Characterizations of the karyotype of other species of solitary bees and of the genus Melitoma, coupled with the use of banding and staining techniques are needed, to obtain a better understanding of the chromosomal evolution in Apidae.
Acknowledgments