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.
Smooth newt
Females and nonbreeding males are pale brown or olive green, often with two darker stripes on the back. Both sexes have orange bellies, although paler in females, which is covered in rounded black spots. They also have pale throats with conspicuous spots. This helps to distinguish them from palmate newts that have pale unspotted throats, and with which they are often confused. When on land, they have velvety skin. During the breeding season, male smooth newts develop a continuous wavy (rather than jagged) crest that runs from their heads to their tails, and their spotted markings become more apparent. They are also distinguishable from females by their fringed toes.