Karyotyp und DNS-Gehalt von Bufo bufo,B. viridis,B. bufo × B. viridis und B. calamita (Amphibia,Anura)

The karyotypes in spermatogonial and leukocyte metaphases of the toads Bufo bufo, B. viridis and B. calamita (all 2n=22) were analysed and the DNA content of colchicine treated and Feulgen stained spermatogonial metaphase chromosomes measured microspectrophotometrically. The toad species possess similar karyotypes, but the chromosomes of B. bufo are somewhat longer than the chromosomes of B. viridis and B. calamita. All chromosomes of B. bufo contain significantly more than, but in no case twice as much DNA as their homologues in the other two species. Eight chromosomes of B. bufo contain 30–40%, three about 50% more DNA than their homologues in B. viridis. Exactly the same DNA-differences between both sets of chromosomes were found in B. bufo × B. viridis hybrids. Significant differences in the DNA amount of B. viridis and B. calamita exist only between the large chromosomes of these species. The ratio of the total DNA amount of the genomes in the three species is 1.49∶1.07∶1. These DNA-differences between the three toad species are confirmed by microspectrophotometric DNA measurements of their erythrocyte nuclei. It is supposed that these interspecific differences in DNA content of the toads are not a consequence of differential polyteny but are caused during the evolution process by local increase in DNA in all chromosomes of B. bufo and in the large chromosomes of B. viridis.