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
There will be a variation in water loss and gain between newts in the aquatic, or winter phase, and the terrestrial, or summer phase. In the terrestrial environment, there will be a change to the integument that will directly affect osmoregulatory mechanisms. This change is the shift from a smooth, mucosal skin surface to one that is rough and dry. This change is to allow easier transport of water through the cutaneous membrane and into the newt to allow for hydration. A mucosal surface is difficult for substances to get through, and is generally attributed to an animal to prevent transport across the epithelium.