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
Arginine, vasotocin, and adrenocorticotropic are hormones secreted by the adrenal glands and are a key component in a newt's regulation of water. In contrast to prolactin, which decreases osmotic permeability, vasotocin increases the permeability and is secreted during the summer months. This hormone is regulated by another major hormone – adrenocorticotropic hormone (ACTH). Arginine vasotocin not only increases cutaneous water permeability, but promotes increased cutaneous blood flow.