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
Prolactin is one of the major hormones released with the changing temperatures, and as such, plays an important role in the transport of sodium and water ions. An increase of this hormone results in the decreased permeability of the skin as well as a reduction of active sodium uptake, which seems to play a less important role than previously thought. This becomes apparent when newts are in their aquatic environment. During winter months, prolactin is released into the circulatory system, which drives "T. carnifex" into the aquatic environment (Lodi 1981). Not only does this hormone prompt a change of habitat for the newt, it reduces the active transport of sodium ions. This happens because there is more water readily available to the newt for uptake as compared to its terrestrial dwelling during the summer months.