Italian crested newt
When newts are inactive or in oxygen-rich environments, respiration can be done through their skin which accounts for 74% of the cutaneous respiration. However, oxygen-poor environments, such as stagnant ponds, pose a threat to the survival of larval newts. This is because oxygen molecules do not readily dissolve in water, and as "T. carnifex" is an immobile animal, extracting oxygen from water is difficult. Newts consequently have external gills at birth that persist until metamorphosis, which assists survival in low-oxygen conditions.
Triturus
Larvae hatch after two to five weeks, depending largely on temperature. In the first days after hatching, they live on their remaining embryonic yolk supply and are not able to swim, but attach to plants or the egg capsule with two balancers, adhesive organs on their head. After this period, they begin to ingest small invertebrates, and actively forage about ten days after hatching. As in all salamanders and newts, forelimbs—already present as stumps at hatching—develop first, followed later by the backlegs. Unlike smaller newts, "Triturus" larvae are mostly nektonic, swimming freely in the water column. Just before the transition to land, the larvae resorb their external gills; they can at this stage reach a size of in the larger species. Metamorphosis takes place two to four months after hatching, but the duration of all stages of larval development varies with temperature. Survival of larvae from hatching to metamorphosis has been estimated at a mean of roughly 4% for the northern crested newt, which is comparable to other newts. In unfavourable conditions, larvae may delay their development and overwinter in water, although this seems to be less common than in the small-bodied newts. Paedomophic adults, retaining their gills and staying aquatic, have occasionally been observed in several crested newt species.