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" displays a unique hemoglobin and red blood cell (RBC) adaptation in their circulatory system. When newts are induced into anemia, they are able to respire without the need of blood cells, or their body making blood cells. Instead, around two weeks after anemia is induced "T. carnifex" produces a mass of cells that helps to revitalize the already circulating red blood cell mass. Casale et al. found that red blood cells of the newt not only produce hemoglobin, but also ferritin, ribosomal proteins, and proteins assumed to be catalase. These extra proteins were produced in high concentrations in early RBC, but decrease quickly as the cell matures. Casale et al. also found that although hemoglobin production decreases as the RBC matures, the cell creates more protein to aid in hemoglobin production.