A The variability of size of AgNORs (black bands) on chromosomes 10 a Pelophylax ridibundus b P. lessonae c P. esculentus RL d P. esculentus RRL e P. esculentus LLR B–E Interphase nuclei of P. esculentus with Ag-nucleoli visualized as black dots by AgNO3B diploid RL with 1 AgNOR C diploid RL with 2 AgNORs D triploid RRL with 3 AgNORs E triploid RRL with 4 AgNORs F metaphase chromosomes and interphase nuclei of the same tetraploid P. esculentus RRLL with 4 sites of hybridization with 28S rDNA probe (FISH) (arrows).