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
Prolactin is one of the major hormones released with the changing temperatures, and as such, plays an important role in the transport of sodium and water ions. An increase of this hormone results in the decreased permeability of the skin as well as a reduction of active sodium uptake, which seems to play a less important role than previously thought. This becomes apparent when newts are in their aquatic environment. During winter months, prolactin is released into the circulatory system, which drives "T. carnifex" into the aquatic environment (Lodi 1981). Not only does this hormone prompt a change of habitat for the newt, it reduces the active transport of sodium ions. This happens because there is more water readily available to the newt for uptake as compared to its terrestrial dwelling during the summer months.