Chromosome mapping of ribosomal genes and histone H4 in the genus Radacridium (Romaleidae)

In this study, two species of Romaleidae grasshoppers, Radacridium mariajoseae and R.nordestinum, were analyzed after CMA(3)/DA/DAPI sequential staining and fluorescence in situ hybridization (FISH) to determine the location of the 18S and 5S rDNA and histone H4 genes. Both species presented karyotypes composed of 2n = 23, X0 with exclusively acrocentric chromosomes. CMA(3)(+) blocks were detected after CMA(3)/DA/DAPI staining in only one medium size autosome bivalent and in the X chromosome in R. mariajoseae. On the other hand, all chromosomes, except the L1 bivalent, of R. nordestinum presented CMA(3)(+) blocks. FISH analysis showed that the 18S genes are restricted to the X chromosome in R. mariajoseae, whereas these genes were located in the L(2), S(9) and S(10) autosomes in R. nordestinum. In R. mariajoseae, the 5S rDNA sites were localized in the in L(1) and L(2) bivalents and in the X chromosome. In R. nordestinum, the 5S genes were located in the L(2), L(3), M(4) and M(5) pairs. In both species the histone H4 genes were present in a medium size bivalent. Together, these data evidence a great variability of chromosome markers and show that the 18S and 5S ribosomal genes are dispersed in the Radacridium genome without a significant correlation.