A review of a rare type of anomaly in amphibians, tail duplication and bifurcation, with description of three new cases in European species (Triturus dobrogicus, Triturus carnifex, and Hyla arborea)

We review the natural occurrence of tail duplications and tail bifurcations in amphibians as well as experimental studies that induced tail duplications. For natural populations, we found 10 publications that mention tail duplications or bifurcations in a total of 24 individual larval amphibians belonging to 15 species, mainly from Europe and South America. Nineteen publications describe the incidence for 34 individual postlarval urodeles from 12 species from North America, Europe, and Asia. Here we add three new observations: a subadult female Triturus dobrogicus with a duplicated tail and an adult female Triturus carnifex with a bifurcated tail from Hungary, and a tadpole of Hyla arborea with a bifurcated tail tip from Greece. The causes of tail duplications in wild amphibians remain unknown. Similar tail anomalies have been obtained in the laboratory when parts of the chorda dorsalis were destroyed, when tar is injected into the tail, or when the lumbar region is irradiated.