Metaphase chromosomes of the species B. insularis (a, c, e) and B. pulchellus (b, d); the chromosome pairs bearing the BOD region are identified with arrows and highlighted in the boxes a, b 18S (red signals) and 5S rDNA FISH (green signals). In the boxes, the argentophilic pattern showed in the BOD regions and the DAPI staining pattern, respectively c, d Distribution of the Tol2 element in the chromosomes. An accumulation of Tol2 sequences is perceptible in the BOD regions e - Distribution of the Alu transposable element on the chromosomes of B. insularis. Scale bar: 5μm.