Newt
During the subsequent few months, the larvae undergo metamorphosis, during which they develop legs, and the gills are absorbed and replaced by air-breathing lungs. Some species, such as the North American newts, also become more brightly coloured during this phase. Once fully metamorphosised, they leave the water and live a terrestrial life, when they are known as "efts". Only when the eft reaches adulthood will the North American species return to live in water, rarely venturing back onto the land. Conversely, most European species live their adult lives on land and only visit water to breed.
Italian crested newt
"T. carnifex" faces an interesting challenge, one that all air-breathing aquatic newts must face: the temperature variance between the land phase and the aquatic phase. Since water has a heat capacity 3500 times greater and a thermal conductance 23 times greater than air, small ectotherms such as the Italian crested newt are likelier to have a more variable body temperature than strictly terrestrial organisms. Many ectotherms possess the ability to reversibly alter their preferred body temperature based upon the seasonal changes the newt experiences, which means that their optimal thermal range is quite wide. They respond to variance in temperature by employing either behavioural or physiological changes. Some changes in body temperature are unavoidable, however, depending on how much solar radiation is available.