Figure 5.

Schematic overview of selective genome elimination in diploid (left) and triploid (right) hybrid tadpoles. (A) Classical scheme of the reproduction of diploid and triploid hybrid frogs. (B) Suggested simplified scheme of gradual chromosome elimination via micronucleus formation in diploid and triploid hybrids. Individual chromosomes were detected via the visualization of centromeric regions with CREST antibodies (red circle) and FISH with a probe specific to the P. ridibundus RrS1 centromeric repeat (green circle). Each micronucleus usually comprises only one chromosome. In the micronuclei, chromatin accumulates heterochromatin markers, indicated by the yellow asterisk (according to Chmielewska et al.²⁵). Subsequently, micronuclei accumulate autophagosome marker LC3 (transparent blue micronuclei) and undergo degradation (according to Chmielewska et al.²⁵). In diploid hybrid frogs, after the elimination of the P. lessonae genome, P. ridibundus chromosomes undergo endoreplication, leading to a doubled number of chromosomes. Cells in which both genomes are eliminated probably die.