2005 Volume 70 Issue 4 Pages 373-380
The tribe Meliponini comprises several hundred species of stingless bees which are major pollinators of many tree species. In the present work we studied two Partamona species: Partamona helleri and Partamona seridoensis. Both species presented similar karyotypes with 2n=34 chromosomes for females, pericentromeric heterochromatic blocks and terminal GC rich heterochromatic segments in chromosome pairs 2, 9, 10 and 15, as shown by sequential C banding-DA/CMA3 staining. The heterochromatin is heterogeneous: pericentromeric and the terminal blocks behave quite differently. FISH with 18S rDNA probe showed that NORs were in terminal blocks. In addition, B chromosomes were observed in P. helleri. The results of the different treatments employed such as C banding and fluorochrome staining led us to believe that their origin was not due to non-disjunction of A genome chromosomes. Supernumerary pericentromeric heterochromatin and the non-homologous portion of a heteromorphic pair behaved in a similar fashion, indicating that may be originated by fission. The FISH assay showed, however that there was no sequence correspondence between these segments.