- Partial neoteny: Tadpoles of Hyla arborea, Rana escülenta during winter will show simple retardation of metamorphosis beyond the normal period.
- Total neoteny: It will retain its gills and becomes sexually mature.
In neoteny, the physiological (or somatic) development of an animal or organism is slowed or delayed.
Ultimately this process results in the retention, in the adults of a species, of juvenile physical characteristics well into maturity.
In vertebrate biology, neoteny is most easily identified when sexually mature, completely viable juveniles or larva are found.