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.
Italian crested newt
The gills have their origins in gill arches 2, 3, and 5; these increase with 3 more bars, that consist of secondary filaments, which create the respiratory organ. In the secondary lamellae there are connective tissues that provide support to the epithelium; these make up the water-blood barrier, in particular where the capillaries are immediately below the basal cells. There are numerous secondary filaments along with the main filaments, which are lengthened to extend the oxygen-catching capability. This increase in surface area counteracts the decreased oxygen available, by allowing greater oxygen uptake. In larval stages, the gills are well-developed with a great number of respiratory lamellae. This adaptation is hypothesized to be an advantage in response to the conditions in an aquatic environment.