The genus
Radacridium (Romaleidae) is endemic in the Northeast region of Brazil and is chromosomally described here using specimens collected in the Agreste (
R. mariajoseae) and in the Caatinga (
R. nordestinum), State of Pernambuco. Both species presented 2n = 23, XO in males and acrocentric chromosomes. The two species can be distinguished on the basis of C-banding patterns and location of the nucleolar organizer regions (NORs). R. mariajoseae showed C-bands only in the pericentromeric regions of autosomes L1, M9, S10 and S11 and in the proximal regions of L
2. Chromsome X presented proximal and distal pericentromeric bands. R. nordestinum, in turn, has pericentromeric bands in all chromosomes and interstitial bands in pairs L
2 and M
5. The bivalent M9 corresponds to the megameric chromosome for the two species. Furthermore, R. nordestinum presented four chromosome pairs (L
3, M
4, M
6, M
7) bearing supernumerary heterochromatin segments that were absent in
R. mariajoseae. In
R. nordestinum a comparative analysis of standard karyotypes and karyotypes with an interstitial supernumerary segment in pair 4 revealed chiasma redistribution in all chromosome groups, with no change in mean chiasma frequency per cell. The nucleolar organizer chromosome was the X in
R. mariajoseae and the L
2 pair in
R. nordestinum. Cores and kinetochores stained identically in the two species. Taken together, the chromosome data show that these species are cytogenetically well distinct.
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