Newt (Chordate)-Hudson Chavre

external image E-Newt8_young.jpg

Kingdom: Animalia

Phylum: Chordata

Class: Lissamphibia

Order: Caudata/Urodela

Family: Salamandridae

Newts typically grow to about two to six inches, with slender bodies, short legs, and long tails. They exist in a variety of colors, the most common ones being green, brown, red, orange, and yellow and have spots. (1)(Shwetha)

Newt gender can easily be distinguished by examining the coloring on their back. Male newts have a single black line running down the center of their backs, while females have two parallel lines on either side of their backs. (1) (SJ)

Newt external characteristics. [Source:] (DM)
Newt external characteristics. [Source:] (DM)

Relationship to humans
There are laws prohibiting the killing, destruction and the selling of newts. While the species is by no means endangered, IUCN lists insufficient data to make an assessment for two of the subspecies. In the UK, the Common newt is protected under Schedule 5 of the Wildlife and Countryside Act with respect to sale only. It is therefore illegal to sell individuals of the species, but their destruction or capture is still permitted.

Newts are able to regrow limbs, and scientists are studying the connection between the cells that rapidly reproduce to regrow limbs and human cells that reproduce and form cancerous tumors. Scientists have found that the chemicals made in a newts body during regrowth are the same chemicals that cause cancer in other animals. Further studies on this connection may lead to more effective cancer treatments for humans. [1] (SM)

People commonly keep newts as pets because they are small, quiet, and some species can live long, up to 27 years old. (7)(KG)
Newts are a species of salamanders. Salamander is a name for an entire order of amphibians that have tails as adults. Not all salamanders are newts.(15)(KG)

Although many newts do produce toxins that are hazardous to humans, most of these toxins are only harmful when ingested. It is for this reason that newts are considered completely safe for humans to possess as pets, provided they do not eat their pets. (17)(BS)

Pet Newt (CC)

Habitat and niche
All newts live in moist habitats to avoid dehydration. Some fully aquatic newts cannot survive long out of water. Newts preferred areas such as, log margins and deciduous forests.
Newts live in the deciduous and coniferous forests. Depending on their stage in live, they live on land or in the water. Fully mature newts can live on land but they prefer to live in moist environments. The juvenile, or eft, stage live on lakeshores and woodland habitats. The larvae stage must live in water and are usually found in lakes, ditches, and marshes with mud bottoms.(LC) 8
Predator avoidance
Predator avoidance is essential to minimize the predation risks of all organisms because the prey never enters the perceptual field of being predator. For toxic animals such as the newt are the best at avoiding prey because of the prey’s inability to consume the toxin secreted by the newt and survive. Newts also release an “alarm” substance when certain predators are present. This alarm substance that alters the behavior of other newts within the area this is a way of warning newts of a predator presence.
Nutrient acquisition
Newts mostly feed upon insects, caterpillars, worms and slugs which are their main diet upon land. In the water the newts feed on insects, crustaceans, mollusks, and tadpoles. When the newts are in water they do not use their tongues to catch prey, however, they use their teeth to catch prey. Newts mostly hunt for prey in shallow waters.

Eastern Newts, for example, have an interesting method of capturing prey on land, involving several steps: 1) They move in closer to the prey upon seeing slight or obvious movements, 2) They will practically pin the prey down with their snouts and take a few seconds to smell what they are about to ingest, 3) The tongue is extended to trap the prey, while the mouth encloses to secure its capture. (14) (MC)

Reproduction and life cycle
In order for the male to find a mate the male must go in front of a female and vibrate his tail. When the male is vibrating his tail he fans glandular secretions in the female’s direction. This signals the female to approach the male. The male then deposits a sperm capsule also commonly known as a spermtophere in front of the female. The female then maneuvers herself in a position where she can place the spermtophere in her cloaca. After a couple of days the female begins to lay eggs, usually under the leaves of an aquatic plant. The female usually lays up to 7-12 eggs per day After 3 weeks the eggs hatch and they feed off the yolk found in the eggs. Newts are born with gills however, they soon metamorphasize into air breathing organisms. Newts are sexually mature by the age of 3 years old. The average lifespan for a newt is 6 years old.

A newt generally lays its eggs in ponds or slow-moving streams, but uniquely it lays the eggs individually. The female can lay up to 400 eggs at a time and tends to lay them on submerged rock or vegetation. Each individual newt egg attaches itself to an aquatic plant, and then hatches three weeks later. The key difference between newt and frog/toad eggs is that the newt lays each egg individually that then attaches to a plant before hatching, while the frog eggs are found in clumps (hundreds) and float closer to the water surface. (7) (PS)

After hatching, newts undergo a larval stage in which they can be compared to fish in that they have gills for respiration, tails for propulsion, and a lateral line system to detect water movement. Through metamorphosis, larvae develop distinct extremities, coloration, and caudal characteristics and go on to become terrestrial or semi-aquatic juveniles. The gills are absorbed, gill slits close, and the skin becomes less permeable as there is less of a need to absorb oxygen through skin. In addition, the eyes adjust, the legs become stronger to support weight and move on land, and the tail is reduced with no need to use propulsion. (4) (JF)

After metamorphosis newts leave there aqueous environments and live on land to mature. during this time period they are called efts. once the newt is fully mature it will return to the water to reproduce. The newt may live as an eft on land for years before returning to the water. (6)(BH)

As adults, newts hibernate until around March. Spring is mating season from March until mid-May. The adult newts leave the water during July. They are primarily nocturnal animals, and sleep under rocks or other protection during the day. (1) (SJ)

external image C.o.egg.JS.jpg (JLau)

Growth and development
As newts grow and develop larger red blood cells are replaced with smaller red blood cells when they become adults. The newts’ gills are also replaced by fully developed lungs as they grow and develop as well.
Newts have the ability to make again eyes ,legs, spinal cords,intestines, jaws , and hearts meaning that if a body part of the newt is injured, then make another or whatever body part was hurt.(13)(NC)
In addition to the 3 part metamorphosis, Newts begin to develop from the egg and they grow their mouth shapes and leg buds. But what is most apparent and rather early is the appearance of gills show in the larvae stage! (18)(ES)
The skin of a newt is fairly rough; the rough skin provides a great surface for water absorption. Although the newts’ skin is rough their skin is fairly thin. Due to the fact that the newts’ skin is very thin water is able to cross the skin membrane through the process of diffusion. Oxygen in the water in the water can diffuse through the newt’s skin straight into the blood through capillaries.

An image of the rough integument of the newt. (9) (E.S.S.)

Newts have 4 legs and a tail on land they use their four legs to maneuver around and in water they use their four legs long tail to propel through the water.
One may ask "Why does a newt wiggle that way?" Newts have very short legs, so mobility is a little restrained. Some newts who live mostly in water don't even have hind legs, so land newts do the best they can. They bend their body from side to side to walk. They use their tails to balance themselves out while walking and to quickly propel them through water if they need to.(1)(Shwetha)
Waste removal
Newts excrete nitrogen in the form of urea and cannot produce urine that is more concentrated than the blood. The urine is stored in the bladder before being voided, providing a reserve of water for when the newt comes on land.

The process of waste removal in amphibians goes as the explained. After passing the esophagus, the food enters the stomach were a great deal of digestion occurs. Pancreas, liver, and the gall badder release enzymes to aid digestion. The food then enters the large intestine and subsequently the colon. After the colon, a cloaca, a muscular cavity, excretes sperm, eggs, urine (enters cloaca through tubes called ureters) and waste. Kidneys will filter waste in the blood. (AWC) [2]

Sensing the environment
When a newt leaves the water a lot of physiological adjustments are made in order to conserve water. The rate of glomerular filtration is reduced by restriction of blood supply and this will also increase the release of ADH.
Newts are capable of thermoregulation and modify their behavior depending on the season. Studies have shown links between the changes in the activity of some muscle metabolic enzymes and in the behavior of the newts in a thermal gradient. For example, the activity enzyme cytochrome c oxidase was completely compensated for by the newt's metabolism when the organism had become acclimated to the cold winter temperatures. (11)(BB-V)

Gas exchange
Newts exchange gas through their skin, gills, and lungs

Newts, like other amphibians, utilize cutaneous respiration - or gas exchange directly across the skin (gas exchange also occurs across the mouth and pharynx). When a newt is completely submerged in water, all gas exchange occurs over the skin. There are two reasons why the skin of newts can function as a respiratory organ out of the water as well. The first reason is that newts' skin is contains many glands whose secretions keep the skin moist, allowing the exchange of carbon dioxide and oxygen (which both require a moist surface in order for gas exchange to occur). The second reason is that amphibian skin has a rich supply of capillary beds, making gas exchange between the blood and the environment easier.(5) (JLev)
Environment physiology
Most amphibians such as the newt try to avoid daytime, low humidity, and try to stay in a shaded area during high temperatures. Due to the fact that newts have body temperatures close to their environments they must remain in areas with high humidity and low temperatures to increase their chances of survival.

Internal circulation
Newts have a 3 chambered heart with 2 atria and one ventricle. Blood flows from the lungs and goes to the left atrium. Blood from the body goes to the right atrium. Both atria empty into ventricle where some mixing occurs. The advantage is that in high pressures in vessels that lead to both the lungs and the body.
The disadvantage to this system is that Newts, like other animals with 3 chambered hearts (such as lizards) would tire easily due to a mixing of oxygenated and deoxygenated blood within its veins, since not all of the blood passes through the pulmonary system before moving to the rest of the body, although this is not a problem because newts are slow-movers. (16)(KG).
Chemical control
The endocrine system plays a key role in newts. For example, hormones are hypothesized to be responsible for limb regeneration in newts. When a newt loses a limb, it is likely that the peptide hormone, insulin, is released. This is thought to signal damaged tissues to divide and differentiate, allowing the newt to grow a new limb to replace the one that was lost. [3] (FZ)

Review Questions:
1. What about the newt's integument allows it to exchange gases directly through the skin? Include at least three reasons. (AA)
2. Compare the method of gas exchange in a newt to the gas exchange in a fish (aquatic organism) and a human (land organism)? (AY)
3. How is having a 3 chambered heart both an advantage and disadvantage for the newt? (WSS)
4. Explain the advantages of the newts skin. (DA)
5. How does leaving water allow a newt to sense their environment?
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16. BSCS Biology. a Molecular Approach. New York: Glencoe/McGraw-Hill, 2006. Print.