Examples of FISH with both 18S rDNA (green) and telomeric DNA (red) loci (a–j) and C-banding heterochromatin (a′-j′) of bivalents in diakinesis for the following Podisma sapporensis: X0-1,-2 (a–c,a′–c′) and XY-2 (d,d′); X0-3 (e,e′) and XY-4 (f,f′); X0-4 (g,g′), Co-1 (h,h′,i,i′); X0-10 (j,j′). The marked bivalent/s (number) and sex chromosome/s indicate the presence of rDNA clusters compared with the C-banding pattern; hybridization signals and the position of C-bands vary in size/position between homologous chromosomes (compare with Table 1) which are marked with an asterisk (*); (a,c) the insert in the left corner shows heterozygous M4 chromosomes forming a loop, indicating a partial absence of homology. B - indicates a metacentric supernumerary chromosome without rDNA probes (b,c) and C-bands (b′,c′); the insert in the bottom left corner (c′) shows this B chromosome in spermatogonial metaphase. 3 h - indicate heterozygous bivalent M3 (a,a′,c,c′,d,d′,f,f′); t - translocation between some chromosomes (i,i′,j). White arrows showed the presence of interstitial hybridization signals (ITSs) in long/medium autosomes (b,c,g) or during translocation between some of the bivalents (j). X/XY, sex chromosome/s. Scale bar = 10 µm.