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
Development brings many changes about in the Italian crested newt. One of these is the alteration from oxyconformer to oxyregulator. Obviously, this difference will change how the newt deals with changes in its respiratory conditions. Another developmental change is the loss of external gills from juvenile stage to adulthood. This affects "T. carnifex" as the difference between being able to outreach the DBL (juvenile) and the inability to do this (adult). This inability introduces a diathesis to hypoxia in stagnant water. This is because there is a lack of convection in the water, and the oxygen is being subtracted more quickly than it can diffuse (due to oxygen’s slow diffusion constant through water).