Newt

external image 225px-Notophthalmus_viridescensPCCA20040816-3983A.jpg



1. Classification/diagnostic characteristics-
An amphibian is a vertebrate that can live in water as a larva and on land as an adult. They are also covered in moist skin containing mucus glands and lack scales and claws. They're skin often dries out quickly when exposed to dry air. All amphibians are cold blooded and most have four legs. There are three main types of amphibians,salamanders, long tailed amphibians, caecilians, legless amphibians, and anurans, long legged, tailess amphibians like toads and frogs.Newts are a member of the family salamandridae, though not all salamanders are considered newts.
(https://en.wikipedia.org/wiki/Newt) Most newts are two to six inches long. They have slender bodies, short legs, and long tails. Newts are greenish, brownish, or blackish above, and yellowish, orangish, or reddish below. The body is typically striped or spotted. (http://animals.howstuffworks.com/amphibians/newt-info.htm)

2. Relationship to humans-
Amphibian populations among the world are decreasing in size and scientists believe either humans or fungi are to blame. Many hypothesis have been formed involving pollution, various habitat alterations, an increase in radiation, and a spread in a pathogenic chytrid fungus. This fungus has been documented in several parts of Central America and has been wiping out many species of amphibians including the Costa Rican golden toad.
The Taricha Granulosa newt produces enough tetrodotoxin to kill an adult human. Some Native Americans in the Pacific Northwest used this toxin to poison their enemies. Natives from South America would use the poison from the poison-dart frog to coat the tips of their arrows. (http://ww.scienceclarified.com/Al-As/Amphibians.html) These poisons are only dangerous when ingested. By touch alone they are harmless.(http://www.buzzle.com/articles/newt-pet.html)

3. Habitat and niche-
Since their offspring need to live in water, while their adult forms live on land, amphibians live near water. They are most common in warm wet areas like tropical rain forests for this reason. Depending on the type of newt, the organism may be classified as aquatic, semi aquatic, or terrestrial. As a result very few amphibians live in areas like the desert, but some do exist. These amphibians are adapted for these low water conditions and some can stay inactive until it rains.

Newts live in the deciduous and coniferous forests. Adult newts live on land but they like to live in moist environments. When the newts are in their juvenile stage, they will live on lake shores and woodland habitats and when in the larvae stage will live in water most commonly found in lakes and marshes.
http://animaldiversity.ummz.umich.edu/site/accounts/information/Notophthalmus_viridescens.html

Despite being nocturnal, newts rely heavily on light for regulation of their seasonal clocks.
http://www.anapsid.org/sallies.html

external image centralnewt.jpg
4. Predator avoidance-
Amphibians are prey to many birds and mammals. As a result amphibians have several ways to avoid predators. One way they avoid predators is through camouflage as many have skin patterns that allow them to blend in with their surroundings. Another way amphibians avoid predators is through exfoliating a poisonous substance through their skin. Further, because amphibian skins is covered in mucus, it is difficult for predators to maintain a sturdy grip on their prey. The Newt's muscle contractions that help it move come in handy when gripped by a predator. The slippery, squirming newt can escape quickly. (http://animals.howstuffworks.com/amphibians/newt-info.htm) On another note, Newts produce toxins to avoid predators. They will leave toxins in their so that when an organism digests these toxins, it will make them sick.(http://en.wikipedia.org/wiki/Rough-skinned_newt).newt.jpg
Additionally, they have the capacity to regrow limbs. This often leads to the tactic of allowing a predator to eat a tail or leg, then escaping an allowing the mutilates limb regrow.
The image above shows a newt that has evolved to be red so as to trick predators into thinking it is toxic, thereby making them less desirable as prey.

5. Nutrient acquisition-
The feeding habits of amphibians change greatly as they develop. As larvae most amphibians are herbivores that eat algae. These larvae have long coiled intestines designed to break down this plant material. As they mature their digestive system and feeding apparatus drastically changes to a carnivorous life style. Legless amphibians use their large jaws to shut and capture their prey while other amphibians like frogs and salamanders have long tongues for catching insects. Newts eat a range of small insects such as pillbugs, beetles, earthworms, small millipedes, insects, aphids (for young larvae), small moths, and other flying insects. Some newts even consume small aquatic invertebrates such as small crustaceans, like brine shrimp, and water fleas. In captivity, newts are primarily fed bloodworms, but their diets must be varied in order to receive the adequate nutrition to survive as they would in their natural environments. (http://www.anapsid.org/sallies.html)

6. Reproduction and life cycle-
Though they share a general [[#|life cycle]], amphibians mating patterns differ through species. In general Amphibian eggs dry out quickly and need to be kept moist to survive. As a result most species of amphibians fertilize eggs externally while some species like salamander species fertilize eggs internally. For the species that fertilize eggs externally, the female lays hundreds of eggs in the water. Then male members of the species come by and fertilize the eggs. Once the eggs hatch the offspring usually resemble fish. As they mature, most amphibians grow limbs and lose their gills in exchange for lungs and move from the water onto land. Other species of newt such as the red-spotted newt will instead lay eggs one at a time on an individual plant for each egg, using a sticky substance to keep the eggs in place. This process can take months to complete. (http://animals.howstuffworks.com/amphibians/newt-info.htm)

7. Growth and development-
Like many other animals, amphibians' lives start out in a fertilized egg. This egg is enclosed with membranes that dry out quickly and cannot prevent water loss. Once the egg is hatched the amphibian is a fish like creature with no legs and a small tail along with gills. As it develops, depending on the amphibian, the gills become enclosed and legs begin to form.
For newts of some species it is possible to remain in larval from for the duration of their life but still reproduce.(http://animals.howstuffworks.com/amphibians/newt-info.htm) At this time the tail begins to shrink down and the amphibian begins to breathe with lungs instead of gills. Newts have an aquatic larval stage followed by a juvenile (terrestrial) stage, then they become adults. This allows for newts to occupy niches in both the aquatic and terrestrial food webs. (http://www.oberlin.edu/library/friends/research.awards/williams.pdf) Another ability amphibians have is their regenerative ability allowing damaged limbs to regrow quickly.(http://a-z-animals.com/animals/newt/)

Newt Image: Newt's life cycles are generally defined in three stages, egg, larval, and adult. Newts live around 15- 20 years. (http://www.ehow.com/how-does_5159376_newt-life-cycle.html)
newt life cycle.jpg


8. Integument-
Most amphibians have skin that is covered in mucus, however some have tough skin to prevent water loss. The amphibians with mucus covered skin can not live in a dry habitat because of their skin. Many amphibians lack scales, but a small amount do have them.

9. Movement-
As larvae amphibians move just like fish as they wiggle their bodies and use their tails for propulsion. As adults most amphibians walk like most four legged creatures. Most frogs and toads have strong back legs allowing them to jump great distances. Other species of frog use their strong back legs with a combination of suction cup like fingers to cling to trees. Salamanders have legs that stick out sideways. When these animals run they move their body in an S-shape and use their hind legs to push back against the ground.

10. Sensing the environment-
Amphibians often have great sight and hearing. Even so, newts in particular, and other members of the caudata clade, actually have no external ear, and thus can't "hear" in the traditional sense like humans do. There is no way for them to pick up sound waves that travel through the air, but they compensate by sensing ground vibrations with their feet, and then analyzing these vibrations to process and identify things in the environment around them. (http://newt150.tripod.com/whatisanewt.shtml)

11.Gas exchange-
All animals must have oxygen to live. They need a means to gather oxygen from the surrounding water or air and release respiratory byproducts, including carbon dioxide. Mammals and reptiles do this with lungs, but amphibians rely on a combination of gas exchange via lungs, gills and skin. Not all amphibians have all three means of gas exchange throughout their life cycles. Species that rarely leave the water may keep their gills, while land species typically lose theirs as they mature.
Most amphibians start life with gills. These are heavily vascularised structures that facilitate gas exchange. Frogs and toads hatch in water as tadpoles -- limbless tailed creatures that need an aqueous environment to live. Their primary gas exchange is via primitive internal gill structures. As they sprout limbs, lose their tails, and grow into their adult forms, their gills seal as their lungs develop. Aquatic amphibians like the axolotl and certain species of salamander retain their gills into adulthood. Some species have dramatic feathery "headdresses" that are actually external gills for taking in oxygen from the surrounding water.
Amphibians can also respire through their soft, thin skin. The skin contains an extensive vascular network of capillaries which allow for gas exchange to take place just below the epidermis. This type of respiration through the skin is called Cutaneous respiration. Cutaneous respiration is facilitated by pumping air in and out of the mouth where further respiratory gas exchange can take place. The buccal (mouth) cavity has a highly vascularized membrane system that supplements cutaneous respiration in lungless, gill-less salamanders. While this ability helps the animals thrive in water and on land, it also puts them at risk of suffocating if their moist environment becomes too dry. Desiccated tissues don't permit oxygen and carbon dioxide transfer. Amphibians' moist and permeable skins also leave them vulnerable to toxins in their environment. Researchers study amphibian populations as bioindicators of environmental disruption because these creatures are so susceptible to change.
Adult amphibians typically rely on lungs for gas exchange, although they never lose their skin permeability. Unlike mammals who use a diaphragm to pull air into the lungs via negative pressure, amphibians force air into their lungs from their mouths. Amphibian lungs contain fewer alveoli, or air sacs, than do the lungs of creatures that evolved later such as reptiles and mammals.

Taken from the website:
http://www.ehow.co.uk/info_8127276_three-carry-out-gas-exchange.html



12. Waste removal-
Amphibians food starts from the esophagus down into the stomach and later the small intestine where it is digested. Various tubes connect the pancreas, liver, and gallbladder to the stomach. These organs release enzymes and help in digestion. After the small intestine the food goes into the large intestine and then the colon. At the end of the colon is a muscular cavity called the cloaca where sperm, eggs, urine, and waste leave the body of the amphibian. For urine, amphibians have kidneys that filter waste in the blood. The urine travels through tubes called the ureters into the cloaca.

13. Environmental Physiology-
Since the Newt is a cold blooded amphibian, it can not regulate their body temperature internally. Thus, the newt, like all amphibians, are considered ectotherms, organisms that cannot maintain a constant internal body temperature. (Hillis) Since most amphibians need to be near fresh water, so their skin does not dry out, this limits amphibians habitats. Being ectoderms, amphibians depend on the environment to regulate internal temperature, and therefore, will lay out in the sun to warm their bodies, and sit in the shade to cool their bodies.(http://science.jrank.org/pages/6749/Temperature-Regulation-Externally-heated-animals.html) Salts are regulated by the newt's pituitary hormones. Prolactin has been proven to have a significant role in the regulation of sodium in the newt. (http://www.ncbi.nlm.nih.gov/pubmed/6311666)

14. Internal circulation-
In most amphibians the [[#|circulatory system]] is what is called a double loop. The first loop carries oxygen-poor blood from the heart to the lungs. The second loop carries oxygen-rich blood to the rest of the body and takes the oxygen-poor blood back into the right atrium of the heart. Most amphibian hearts are divided into three parts, the left atrium, the right atrium, and the ventricle. Poor oxygen blood comes from the body into the right atrium. At the same time oxygen rich blood enters the left atrium. The atria then contract and the blood goes through the ventricle. The ventricle then contracts and blood pumps into a large blood vessel that then splits into two branches. Due to the way the blood vessels branch, little oxygen rich blood mixes with the oxygen poor blood.
external image circulatory_system_-_amphibian.jpg-
http://www.baileybio.com/plogger/?level=picture&id=1518
15. Chemical control-
In amphibians, the departure from an aquatic environment to a terrestrial one resulted in changes in the hormonal control of calcium homeostasis, or the tendency of a system to maintain stable internal conditions, through the appearance of parathyroid glands. The parathyroid glands of adult amphibians, which spend some time of their life on land, play a major role in calcium homeostasis as well as in a variety of biological processes, such as cell membrane permeability, muscle contraction, neuronal excitability, responses to acid-base balance, and the initiation of many other endocrine events, including hormone release. During the water to land transition, the endocrine control of calcium regulation was modified so that in terrestrial vertebrates calcitonin, a hormone secreted by the thyroid, exerts hypocalcemic effect (reducing blood calcium levels) while vitamin D3 and parathyroid hormone (PTH, for short), which is released from the parathyroid glands, exert hypercalcemic effects (increasing blood calcium levels). In amphibians, the parathyroid glands develop at the time of metamorphosis of the purely aquatic larva into an adult. The major hormone produced by the thyroid gland is thyroxine, which plays a role in metabolic rate, growth, tissue differentiation, and metamorphosis. Furthermore, hormones from the pituitary gland control variations in skin color. (http://www.snow.edu/allans/biology1320/endocrinesystem.html)

https://docs.google.com/viewer?a=v&q=cache:LJFJJ6D245AJ:www.biol.uni.wroc.pl/zoolog/pdf/vol_45_art_02.pdf+amphibian+endocrine+system&hl=en&gl=us&pid=bl&srcid=ADGEESiESKUKygdZwGZbjPrunU4nnGkKSMu16l2Gho6dMWnBSsY0wCloeVS_ZSnwsfLTSWUCXnvFDApoKDJxK5LuBWZeGLc1XC5Lflh5AOaJb7qhdQ6yMp7cJENs88_aoILTjLh2QMjs&sig=AHIEtbQubRyStjNmEPiC-ztH-Slf6HjhEg

Review Questions:
1. Describe the flow of blood form the right side of the heart where there is venous blood present to the left side of the heart where there is arterial blood present, back to the right side of the heart.

2. Describe how the newt uses camouflage, poison excretion, surface mucus, and sudden muscle contractions to avoid predation.

3. Explain what the term "amphibian" refers to and how it affects the habitat and niche of the newt.

4. Newts are categorized as ectotherms, meaning they cannot regulate their internal temperature with just their biological functions alone. How do they maintain a relatively regular body temperature?