How do newts breathe?
2487231#1
"Pachytriton" species are stout-bodied, smooth-skinned aquatic newts. Their heads are large and flattened, and they have conspicuous labial folds and short, stubby legs and toes. They breathe through both lungs and skin. 
"P. brevipes" ranges from 5.5 to 7.5 in as an adult. It has prominent labial folds, long digits, and smooth skin, which differs from the tuberculate skin typical of newts.
Spotted paddle-tail newt
12176781#6
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
19321517#9
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.
Newt
12176781#102
"T. carnifex" faces an interesting challenge, one that all air-breathing aquatic newts must face: the temperature variance between the land phase and the aquatic phase. Since water has a heat capacity 3500 times greater and a thermal conductance 23 times greater than air, small ectotherms such as the Italian crested newt are likelier to have a more variable body temperature than strictly terrestrial organisms. Many ectotherms possess the ability to reversibly alter their preferred body temperature based upon the seasonal changes the newt experiences, which means that their optimal thermal range is quite wide. They respond to variance in temperature by employing either behavioural or physiological changes. Some changes in body temperature are unavoidable, however, depending on how much solar radiation is available.
Italian crested newt
12176781#76
"T. carnifex" are ectotherms. This means that the internal forces of this newt that control the body temperature have almost no importance. They are traditionally called “cold-blooded” although blood has really nothing to do with how these animals thermoregulate. This means that "T. carnifex" will regulate in a way that depends more on behavior. When there is a large range of environmental temperatures, newts are very insensitive to a thermal gradient profile.
Italian crested newt
3136448#11
The rough skinned newt uses a form of chemical based avoidance behavior to evade being eaten by predators, mainly the common garter snake. The snakes, after swallowing, digesting, and metabolizing a rough-skinned newt, release a chemical signature. This stimulus can be detected by a nearby newt and trigger an avoidant response, which allows them to minimize predation risks. In this way, newts are able to differentiate whether a snake is resistant or sensitive to the toxin in order to avoid being preyed upon. However, newts do not avoid the corpses of a recently digested newt that has been left to decompose. This behavior is unlike salamanders that have been documented in avoiding other damaged salamanders.
Rough-skinned newt
2978345#17
Juveniles often disperse to new breeding sites, while the adults in general move back to the same breeding sites each year. The newts do not migrate very far: they may cover around in one night and rarely disperse much farther than . For orientation, the newts likely use a combination of cues including odour and the calls of other amphibians, and orientation by the night sky has been demonstrated in the marbled newt. Activity is highest on wet nights; the newts usually stay hidden during daytime. There is often an increase in activity in late summer and autumn, when the newts likely move closer to their breeding sites. Over most of their range, they hibernate in winter, using mainly subterranean hiding places, where many individuals will often congregate. In their southern range, they may instead sometimes aestivate during the dry months of summer.
Triturus
12176781#95
Wu "et al". (2007) found that when larvae are placed in a homogeneous temperature environment, they do not need to use behavioral thermoregulation and instead only use metabolic compensation. However, when placed in an environment with a variation of temperatures, newts will use both behavioral thermoregulation and metabolic compensation. Samajov and Gvozdik (2009) discovered that when adult newts dive at higher temperatures, they reduce the amount of time in their dive in order to reduce the cost on thermoregulation. Samajov and Gvozdik did not take into consideration that newts respire aerially, as well as cutaneously, and so the frequency and the duration of the dives recorded could have been affected by the amount of dissolved oxygen in the water. Adult newts alter the speed in which they dive between descents and ascents. Descents affect thermoregulation by using more energy, and so newts will often choose a passive descent, rather than swimming down to forage for food. When "T. carnifex" ascends, thermoregulation is not as affected because newts have been known to increase their buoyancy by expelling excess gasses. By altering the behavior used as a larvae and when swimming, "T. carnifex" can effectively thermoregulate.
Italian crested newt
12176781#64
Temperature plays a key role in the osmoregulation of the newt. Not only do the changing seasons drive "T. carnifex" either into the water or onto land, it also regulates the release of certain hormones in accordance with the osmotic permeability of the newts' epidermis. Osmotic permeability is dependent on the release of hormones such as prolactin, vasotocin, as well as other thyroidal and internal hormones. Brown et al. experimented on a close relative of "T. carnifex" to determine the effects different environmental conditions have on the newts osmoregulatory systems.
Italian crested newt
20866#17
In newts, there is no true metamorphosis because newt larvae already feed as predators and continue doing so as adults. Newts' gills are never covered by a gill sac and will be resorbed only just before the animal leaves the water. Just as in tadpoles, their lungs are functional early, but newts use them less frequently than tadpoles. Newts often have an aquatic phase in spring and summer, and a land phase in winter. For adaptation to a water phase, prolactin is the required hormone, and for adaptation to the land phase, thyroxin. External gills do not return in subsequent aquatic phases because these are completely absorbed upon leaving the water for the first time.
Metamorphosis
12176781#18
The heart of "Triturus carnifex", like that of most amphibians, consists of two atria and one ventricle. Blood flows from the anterior and posterior caval veins into the right atrium; blood that entered the heart from the left atrium is then expelled out of the ventricle. Newts do not have a coronary artery on the ventricle, due to circulation that is found in the conus arteriosus. Newts contain a special circulatory adaptation that allows them to survive ventricular penetration. Myachi found that when a newt’s ventricle is punctured, the heart will divert the blood directly into an ascending aorta via a duct located between the ventricle and the conus arteriosus. "T.carnifex" begins to regenerate the ventricle by a thickening of the epicardial layer that protrudes to allow the new vessels to form, and concludes with a regeneration of the entire myocardial wall.
Italian crested newt