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148-1069: Salamandrella keyserlingii , the Siberian salamander , is a species of salamander found in Northeast Asia . It lives in wet woods and riparian groves. It is found primarily in Siberia east of the Sosva River and the Urals , in the East Siberian Mountains , including the Verkhoyansk Range , northeast to the Anadyr Highlands , east to the Kamchatka Peninsula and south into Manchuria , with outlying populations also in northern Kazakhstan and Mongolia , northeastern China , and on

296-419: A blastema that proliferates and grows to repattern the missing tissue. Arachnids , including scorpions, are known to regenerate their venom, although the content of the regenerated venom is different from the original venom during its regeneration, as the venom volume is replaced before the active proteins are all replenished. The fruit fly Drosophila melanogaster is a useful model organism to understand

444-440: A bony cavity. Rhodopsin regeneration has been studied in skates and rays. After complete photo-bleaching, rhodopsin can completely regenerate within 2 hours in the retina . White bamboo sharks can regenerate at least two-thirds of their liver and this has been linked to three micro RNAs, xtr-miR-125b, fru-miR-204, and has-miR-142-3p_R-. In one study, two-thirds of the liver was removed and within 24 hours more than half of

592-413: A concealed site in flowing water, and these are usually guarded by an adult, normally the female. Many of the tropical climbing salamanders ( Bolitoglossa ) and lungless salamanders (Plethodontinae) lay a small number of large eggs on land in a well-hidden spot, where they are also guarded by the mother. Some species such as the fire salamanders ( Salamandra ) are ovoviviparous , with the female retaining

740-420: A female typically laying up to 240 eggs in a season. The light-brown eggs hatch three to four weeks after being laid, releasing larval salamanders of 11–12 mm in length. Salamander Cryptobranchoidea Salamandroidea Salamanders are a group of amphibians typically characterized by their lizard -like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to

888-586: A flash of warning hue on its underside. The red eft, the brightly colored terrestrial juvenile form of the eastern newt ( Notophthalmus viridescens ), is highly poisonous. It is avoided by birds and snakes, and can survive for up to 30 minutes after being swallowed (later being regurgitated). The red salamander ( Pseudotriton ruber ) is a palatable species with a similar coloring to the red eft. Predators that previously fed on it have been shown to avoid it after encountering red efts, an example of Batesian mimicry . Other species exhibit similar mimicry. In California,

1036-433: A fourth of their body weight through water loss and liver shrinkage, and by increasing the concentration of glycerol in their body. In 1870,Dybowski gave it the name of Salamandrella Keyserlingii.It was renamed in 1910,the 1910 scientific name hardly used.Boulenger gave it the new(but unused) name. The Siberian salamander is fairly nocturnal, foraging above ground at night and staying under moist logs or woody debris during

1184-474: A high degree. Usually, it involves dropping a section of their tail and regenerating it as part of a defense mechanism. While escaping a predator, if the predator catches the tail, it will disconnect. Ecosystems can be regenerative. Following a disturbance, such as a fire or pest outbreak in a forest, pioneering species will occupy, compete for space, and establish themselves in the newly opened habitat. The new growth of seedlings and community assembly process

1332-416: A hissing sound, while the sirens sometimes produce quiet clicks, and can resort to faint shrieks if attacked. Similar clicking behaviour was observed in two European newts Lissotriton vulgaris and Ichthyosaura alpestris in their aquatic phase. Vocalization in salamanders has been little studied and the purpose of these sounds is presumed to be the startling of predators. Respiration differs among

1480-438: A lateral row. This may provide an aposematic signal that makes the spines more visible. When the danger has passed, the ribs retract and the skin heals. Although many salamanders have cryptic colors so as to be unnoticeable, others signal their toxicity by their vivid coloring . Yellow, orange, and red are the colors generally used, often with black for greater contrast. Sometimes, the animal postures if attacked, revealing

1628-665: A long body, a laterally flattened tail with dorsal and ventral fins and in some species limb-buds or limbs. Pond-type larvae may have a pair of rod-like balancers on either side of the head, long gill filaments and broad fins. Stream-type larvae are more slender with short gill filaments—in Rhyacotriton and Onychodactylus, and some species in Batrachuperus, the gills and gill rakers are extremely reduced, narrower fins and no balancers, but instead have hind limbs already developed when they hatch. The tadpoles are carnivorous and

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1776-447: A mammal that can be regrown every year. While reparative regeneration is a rare phenomenon in mammals, it does occur. A well-documented example is regeneration of the digit tip distal to the nail bed. Reparative regeneration has also been observed in rabbits, pikas and African spiny mice. In 2012, researchers discovered that two species of African spiny mice , Acomys kempi and Acomys percivali , were capable of completely regenerating

1924-517: A minute fragment of skin is deadly. In feeding trials, fish, frogs, reptiles, birds, and mammals were all found to be susceptible. Mature adults of some salamander species have "nuptial" glandular tissue in their cloacae , at the base of their tails, on their heads or under their chins. Some females release chemical substances , possibly from the ventral cloacal gland, to attract males, but males do not seem to use pheromones for this purpose. In some plethodonts , males have conspicuous mental glands on

2072-437: A new tail proceeds through a blastema-mediated process that results in a functionally and morphologically similar structure. It has been estimated that the average shark loses about 30,000 to 40,000 teeth in a lifetime. Leopard sharks routinely replace their teeth every 9–12 days and this is an example of physiological regeneration. This can occur because shark teeth are not attached to a bone, but instead are developed within

2220-412: A particular gene . In the enhancer regions that are activated during head regeneration, a set of transcription factor motifs commonly occur that appear to facilitate coordinated gene expression. Owing to a limited literature on the subject, birds are believed to have very limited regenerative abilities as adults. Some studies on roosters have suggested that birds can adequately regenerate some parts of

2368-598: A piece corresponding to 1/279th of a planarian or a fragment with as few as 10,000 cells can successfully regenerate into a new worm within one to two weeks. After amputation, stump cells form a blastema formed from neoblasts , pluripotent cells found throughout the planarian body. New tissue grows from neoblasts with neoblasts comprising between 20 and 30% of all planarian cells. Recent work has confirmed that neoblasts are totipotent since one single neoblast can regenerate an entire irradiated animal that has been rendered incapable of regeneration. In order to prevent starvation

2516-641: A planarian will use their own cells for energy, this phenomenon is known as de-growth. Limb regeneration in the axolotl and newt has been extensively studied and researched. The nineteenth century studies of this subject are reviewed in Holland (2021). Urodele amphibians, such as salamanders and newts, display the highest regenerative ability among tetrapods. As such, they can fully regenerate their limbs, tail, jaws, and retina via epimorphic regeneration leading to functional replacement with new tissue. Salamander limb regeneration occurs in two main steps. First,

2664-446: A portion of the elbow joint in a chick embryo via window excision or slice excision and comparing joint tissue specific markers and cartilage markers showed that window excision allowed 10 out of 20 limbs to regenerate and expressed joint genes similarly to a developing embryo. In contrast, slice excision did not allow the joint to regenerate due to the fusion of the skeletal elements seen by an expression of cartilage markers. Similar to

2812-609: A reasonable size. Large species such as the Japanese giant salamander ( Andrias japonicus ) eat crabs, fish, small mammals, amphibians, and aquatic insects. In a study of smaller dusky salamanders ( Desmognathus ) in the Appalachian Mountains , their diet includes earthworms , flies , beetles , beetle larvae, leafhoppers , springtails , moths , spiders , grasshoppers , and mites . Cannibalism sometimes takes place, especially when resources are short or time

2960-433: A second. In some species, the tongue is attached anteriorly to the floor of the mouth, while in others, it is mounted on a pedicel. It is rendered sticky by secretions of mucus from glands in its tip and on the roof of the mouth. High-speed cinematography shows how the tiger salamander ( Ambystoma tigrinum ) positions itself with its snout close to its prey. Its mouth then gapes widely, the lower jaw remains stationary, and

3108-678: A short period of time and involves the closing of the gill slits and the loss of structures such as gills and tail fins that are not required as adults. At the same time, eyelids develop, the mouth becomes wider, a tongue appears, and teeth are formed. The aqueous larva emerges onto land as a terrestrial adult. Not all species of salamanders follow this path. Neoteny , also known as paedomorphosis, has been observed in all salamander families, and may be universally possible in all salamander species. In this state, an individual may retain gills or other juvenile features while attaining reproductive maturity. The changes that take place at metamorphosis are under

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3256-514: A simplified retinal structure, and in cave dwellers such as the Georgia blind salamander , they are absent or covered with a layer of skin. In amphibious species, the eyes are a compromise and are nearsighted in air and farsighted in water. Fully terrestrial species such as the fire salamander have a flatter lens which can focus over a much wider range of distances. To find their prey, salamanders use trichromatic color vision extending into

3404-450: A single spike, a paddle-shaped growth is obtained at the end of the limb by 18 months. Hydra is a genus of freshwater polyp in the phylum Cnidaria with highly proliferative stem cells that gives them the ability to regenerate their entire body. Any fragment larger than a few hundred epithelial cells that is isolated from the body has the ability to regenerate into a smaller version of itself. The high proportion of stem cells in

3552-407: A small lizard, having a basal tetrapod body form with a cylindrical trunk, four limbs, and a long tail. Except in the family Salamandridae, the head, body, and tail have a number of vertical depressions in the surface which run from the mid-dorsal region to the ventral area and are known as costal grooves . Their function seems to be to help keep the skin moist by channeling water over the surface of

3700-437: A top predator since the introduction of locally exotic species such as Nile tilapia and carp. Tilapia and carp directly compete with axolotls by consuming their eggs, larvae, and juveniles. Climate change has also immensely affected axolotls and their populations throughout the southern Mexico area. Due to its proximity to Mexico City , officials are currently working on programs at Lake Xochimilco to bring in tourism and educate

3848-520: Is advanced into the salamander's mouth, the teeth tips relax and bend in the same direction, encouraging movement toward the throat, and resisting the prey's escape. Many salamanders have patches of teeth attached to the vomer and the palatine bones in the roof of the mouth, and these help to retain prey. All types of teeth are resorbed and replaced at intervals throughout the animal's life. A terrestrial salamander catches its prey by flicking out its sticky tongue in an action that takes less than half

3996-566: Is another large, long-lived species with dwindling numbers and fewer juveniles reaching maturity than previously. Another alarming finding is the increase in abnormalities in up to 90% of the hellbender population in the Spring River watershed in Arkansas. Habitat loss, silting of streams, pollution and disease have all been implicated in the decline and a captive breeding programme at Saint Louis Zoo has been successfully established. Of

4144-459: Is being undertaken to assess the status of these salamanders, and to better understand the factors involved in their population declines, with a view to taking action. Ambystoma mexicanum , an aquatic salamander, is a species protected under the Mexican UMA (Unit for Management and conservation of wildlife) as of April 1994. Another detrimental factor is that the axolotl lost their role as

4292-551: Is considered cellular regeneration (a form of compensatory hypertrophy) where the function and mass of the liver is regenerated through the proliferation of existing mature hepatic cells (mainly hepatocytes ), but the exact morphology of the liver is not regained. This process is driven by growth factor and cytokine regulated pathways. The normal sequence of inflammation and regeneration does not function accurately in cancer. Specifically, cytokine stimulation of cells leads to expression of genes that change cellular functions and suppress

4440-624: Is internal. As a general rule, salamanders with internal fertilization have indirect sperm transfer, but in species like the Sardinian brook salamander , the Corsican brook salamander , the Caucasian salamander and the Pyrenean brook salamander , the male transfer his sperm directly into the female cloaca. For the species with indirect sperm transfer, the male deposits a spermatophore on

4588-405: Is known as regeneration in ecology . Pattern formation in the morphogenesis of an animal is regulated by genetic induction factors that put cells to work after damage has occurred. Neural cells, for example, express growth-associated proteins, such as GAP-43 , tubulin , actin , an array of novel neuropeptides , and cytokines that induce a cellular physiological response to regenerate from

Salamandrella keyserlingii - Misplaced Pages Continue

4736-417: Is larger than that of the female, is used during the amplexus embrace to propel the mating couple to a secluded location. In terrestrial species, the tail moves to counterbalance the animal as it runs, while in the arboreal salamander and other tree-climbing species, it is prehensile . The tail is also used by certain plethodontid salamanders that can jump, to help launch themselves into the air. The tail

4884-562: Is limited, because heart muscle cells are nearly all terminally differentiated . MRL mice show the same amount of cardiac injury and scar formation as normal mice after a heart attack. However, recent studies provide evidence that this may not always be the case, and that MRL mice can regenerate after heart damage. The regrowth of lost tissues or organs in the human body is being researched. Some tissues such as skin regrow quite readily; others have been thought to have little or no capacity for regeneration, but ongoing research suggests that there

5032-435: Is limited. Tiger salamander tadpoles in ephemeral pools sometimes resort to eating each other, and are seemingly able to target unrelated individuals. Adult blackbelly salamanders ( Desmognathus quadramaculatus ) prey on adults and young of other species of salamanders, while their larvae sometimes cannibalise smaller larvae. Most species of salamander have small teeth in both their upper and lower jaws. Unlike frogs , even

5180-429: Is mediated by the molecular processes of gene regulation and involves the cellular processes of cell proliferation , morphogenesis and cell differentiation . Regeneration in biology, however, mainly refers to the morphogenic processes that characterize the phenotypic plasticity of traits allowing multi-cellular organisms to repair and maintain the integrity of their physiological and morphological states. Above

5328-465: Is not just limited to limbs but extends to vital organs such as the heart, jaw, and parts of the spinal cord, showing their uniqueness compared to different types of vertebrates. ⁤⁤This ability is most remarkable for occurring without any type of scarring. ⁤⁤This has made salamanders an invaluable model organism in scientific research aimed at understanding and achieving regenerative processes for medical advancements in human and animal biology. Members of

5476-422: Is only found in around 1% of myocytes around the area of injury, which is not enough to restore function of cardiac muscle . However, this may be an important target for regenerative medicine as it implies that regeneration of cardiomyocytes, and consequently of myocardium, can be induced. Another example of reparative regeneration in humans is fingertip regeneration, which occurs after phalanx amputation distal to

5624-444: Is possibly the most adept vertebrate group at regeneration, given their capability of regenerating limbs, tails, jaws, eyes and a variety of internal structures. The regeneration of organs is a common and widespread adaptive capability among metazoan creatures. In a related context, some animals are able to reproduce asexually through fragmentation , budding, or fission . A planarian parent, for example, will constrict, split in

5772-455: Is restricted to the slightly cooler and wetter conditions in north-facing cove forests in the southern Appalachians, and to higher elevations above 900 m (3,000 ft), while the former is more adaptable, and would be perfectly able to inhabit these locations, but some unknown factor seems to prevent the two species from co-existing. One species, the Anderson's salamander , is one of

5920-454: Is some hope for a variety of tissues and organs. Human organs that have been regenerated include the bladder, vagina and the penis. As are all metazoans , humans are capable of physiological regeneration (i.e. the replacement of cells during homeostatic maintenance that does not necessitate injury). For example, the regeneration of red blood cells via erythropoiesis occurs through the maturation of erythrocytes from hematopoietic stem cells in

6068-524: Is the self-amputation of a body part, usually an appendage.  Depending on severity, starfish will then go through a four-week process where the appendage will be regenerated. Some species must retain mouth cells to regenerate an appendage, due to the need for energy. The first organs to regenerate, in all species documented to date, are associated with the digestive tract. Thus, most knowledge about visceral regeneration in holothurians concerns this system. Regeneration research using Planarians began in

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6216-413: Is used in courtship and as a storage organ for proteins and lipids. It also functions as a defense against predation, when it may be lashed at the attacker or autotomised when grabbed. Unlike frogs, an adult salamander is able to regenerate limbs and its tail when these are lost. The skin of salamanders, in common with other amphibians, is thin, permeable to water, serves as a respiratory membrane, and

6364-407: Is well-supplied with glands. It has highly cornified outer layers, renewed periodically through a skin shedding process controlled by hormones from the pituitary and thyroid glands. During moulting, the skin initially breaks around the mouth, and the animal moves forward through the gap to shed the skin. When the front limbs have been worked clear, a series of body ripples pushes the skin toward

6512-706: The Alaska Panhandle . They had an exclusively Laurasian distribution until Bolitoglossa invaded South America from Central America, probably by the start of the Early Miocene , about 23 million years ago. They also lived on the Caribbean Islands during the early Miocene epoch, confirmed by the discovery of Palaeoplethodon hispaniolae , found trapped in amber in the Dominican Republic . Vertebrae fossils recovered from

6660-588: The Appalachian Mountains ; most species are found in the Holarctic realm , with some species present in the Neotropical realm . Salamanders never have more than four toes on their front legs and five on their rear legs, but some species have fewer digits and others lack hind limbs. Their permeable skin usually makes them reliant on habitats in or near water or other cool, damp places. Some salamander species are fully aquatic throughout their lives, some take to

6808-888: The Holarctic and Neotropical regions, not reaching south of the Mediterranean Basin , the Himalayas , or in South America the Amazon Basin . They do not extend north of the Arctic tree line , with the northernmost Asian species, Salamandrella keyserlingii , which can survive long-term freezing at −55 °C, occurring in the Siberian larch forests of Sakha and the most northerly species in North America, Ambystoma laterale , reaching no farther north than Labrador and Taricha granulosa not beyond

6956-617: The Korean Peninsula . It is believed to be extirpated from South Korea . An isolated population exists on Hokkaidō , Japan, in the Kushiro Shitsugen National Park . A breeding ground of Siberian salamanders in Paegam , South Hamgyong , is designated North Korean natural monument #360. Adults are from 9.0 to 12.5 cm in length. Their bodies are bluish-brown in color, with a purple stripe along

7104-618: The Murgon fossil site have been tentatively attributed to that of a Salamander, though its true identity is disputed. If the vertebrae truly belong to a Salamander, they would represent the only Salamanders in Australia . There are about 760 living species of salamander. One-third of the known salamander species are found in North America. The highest concentration of these is found in the Appalachian Mountains region, where

7252-449: The amphiumas , metamorphosis is incomplete, and they retain one pair of gill slits as adults, with fully functioning internal lungs. Some species that lack lungs respire through gills. In most cases, these are external gills, visible as tufts on either side of the head. Some terrestrial salamanders have lungs used in respiration, although these are simple and sac-like, unlike the more complex organs found in mammals . Many species, such as

7400-477: The autotomically released or otherwise damaged tissue. These species can regrow hair follicles, skin, sweat glands , fur and cartilage. In addition to these two species, subsequent studies demonstrated that Acomys cahirinus could regenerate skin and excised tissue in the ear pinna. Despite these examples, it is generally accepted that adult mammals have limited regenerative capacity compared to most vertebrate embryos/larvae, adult salamanders and fish. But

7548-401: The cloud forests of Guatemala and Mexico during the 1970s were found by 2009 to be rare. Few data have been gathered on population sizes over the years and, by intensive surveying of historic and suitable new locations, it has been possible to locate individuals of other species, such as Parvimolge townsendi , which had been thought to be extinct . Currently, the major lines of defense for

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7696-495: The family Salamandridae are mostly known as newts and lack the costal grooves along the sides of their bodies typical of other groups. The skin of some species contains the powerful poison tetrodotoxin ; these salamanders tend to be slow-moving and have bright warning coloration to advertise their toxicity. Salamanders typically lay eggs in water and have aquatic larvae, but great variation occurs in their lifecycles . Some species in harsh environments reproduce while still in

7844-594: The lens or retina of the eye. Within only a few weeks of losing a piece of a limb, a salamander perfectly reforms the missing structure. Salamanders split off from the other amphibians during the mid- to late Permian, and initially were similar to modern members of the Cryptobranchoidea . Their resemblance to lizards is the result of symplesiomorphy , their common retention of the primitive tetrapod body plan, but they are no more closely related to lizards than they are to mammals. Their nearest relatives are

7992-638: The olm , have both lungs and gills as adults. In the Necturus , external gills begin to form as a means of combating hypoxia in the egg as egg yolk is converted into metabolically active tissue. Molecular changes in the mudpuppy during post-embryonic development primarily due to the thyroid gland prevent the internalization of the external gills as seen in most salamanders that undergo metamorphosis. The external gills seen in salamanders differs greatly from that of amphibians with internalized gills. Unlike amphibians with internalized gills which typically rely on

8140-502: The ultraviolet range, based on three photoreceptor types that are maximally sensitive around 450, 500, and 570 nm. The larvae, and the adults of some highly aquatic species, also have a lateral line organ, similar to that of fish, which can detect changes in water pressure. All salamanders lack middle ear cavity, eardrum and eustachian tube , but have an opercularis system like frogs, and are still able to detect airborne sound. The opercularis system consists of two ossicles:

8288-468: The 20 species of minute salamanders ( Thorius spp.) in Mexico, half are believed to have become extinct and most of the others are critically endangered. Specific reasons for the decline may include climate change, chytridiomycosis, or volcanic activity, but the main threat is habitat destruction as logging, agricultural activities, and human settlement reduce their often tiny, fragmented ranges. Survey work

8436-500: The California newt has many large poison glands in its skin, is diurnal, and is avoided by snakes. Some salamander species use tail autotomy to escape predators. The tail drops off and wriggles around for a while after an attack, and the salamander either runs away or stays still enough not to be noticed while the predator is distracted. The tail regrows with time, and salamanders routinely regenerate other complex tissues, including

8584-517: The Plethodontidae are thought to have originated in mountain streams. Here, vegetation zones and proximity to water are of greater importance than altitude. Only species that adopted a more terrestrial mode of life have been able to disperse to other localities. The northern slimy salamander ( Plethodon glutinosus ) has a wide range and occupies a habitat similar to that of the southern gray-cheeked salamander ( Plethodon metcalfi ). The latter

8732-629: The United States and abroad. An NIH -funded NCRR grant has led to the establishment of the Ambystoma EST database, the Salamander Genome Project (SGP) that has led to the creation of the first amphibian gene map and several annotated molecular data bases, and the creation of the research community web portal. In 2022, a first spatiotemporal map revealed key insights about axolotl brain regeneration , also providing

8880-510: The affected area to then flourish with epidermal cells and continued gene expression allows the area to regenerate to its natural being. In spite of the historically few researchers studying limb regeneration, remarkable progress has been made recently in establishing the neotenous amphibian the axolotl ( Ambystoma mexicanum ) as a model genetic organism. This progress has been facilitated by advances in genomics , bioinformatics , and somatic cell transgenesis in other fields, that have created

9028-495: The amputation, migrating epidermal cells form a wound epithelium which thickens, through cell division, throughout the first phase to form a cap around the site of the wound. The cells underneath this cap then begin to rapidly divide and form a cone shaped end to the amputation known as a blastema. Included in the blastema are skin, muscle, and cartilage cells that de-differentiate and become similar to stem cells in that they can become multiple types of cells. Cells differentiate to

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9176-405: The animal of an approaching predator. Salamanders are usually considered to have no voice and do not use sound for communication in the way that frogs do. Before mating, they communicate by pheromone signaling; some species make quiet ticking, clicking, squeaks or popping noises, perhaps by the opening and closing of valves in the nose. Most salamanders lack vocal cords, but a larynx is present in

9324-422: The animal slippery and more difficult for predators to catch. Granular glands scattered on the upper surface, particularly the head, back, and tail, produce repellent or toxic secretions. Some salamander toxins are particularly potent. The rough-skinned newt ( Taricha granulosa ) produces the neurotoxin tetrodotoxin , the most toxic nonprotein substance known. Handling the newts does no harm, but ingestion of even

9472-404: The axolotl does not account for the overall lack of diversity. Evidence points toward a historical bottlenecking of Ambystoma that contributes to the variation issues and no longer a large genetic pool for it to pull from, thus raising concern for inbreeding due to lack of gene flow. One way researchers are looking into maintaining genetic diversity within the population is via cryopreservation of

9620-438: The back. Thin, dark brown stripes occur between and around the eyes, and also sometimes on the tail. Four clawless toes are on each foot. The tail is longer than the body. Males are typically smaller than females. The species is known for surviving deep freezes (as low as −45 °C). In some cases, they have been known to remain frozen in permafrost for years, and upon thawing, walking off. They accomplish this by reducing to

9768-464: The blastema forms, pattern formation genes – such as Hox A and HoxD – are activated as they were when the limb was formed in the embryo . The positional identity of the distal tip of the limb (i.e. the autopod, which is the hand or foot) is formed first in the blastema. Intermediate positional identities between the stump and the distal tip are then filled in through a process called intercalation. Motor neurons , muscle, and blood vessels grow with

9916-544: The body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela from the group Caudata . Urodela is a scientific Latin term based on the Ancient Greek οὐρά δήλη : ourà dēlē "conspicuous tail". Caudata is the Latin for "tailed ones", from cauda : "tail". Salamander diversity is highest in eastern North America , especially in

10064-402: The body. Some aquatic species, such as sirens and amphiumas , have reduced or absent hind limbs, giving them an eel -like appearance, but in most species, the front and rear limbs are about the same length and project sideward, barely raising the trunk off the ground. The feet are broad with short digits, usually four on the front feet and five on the rear. Salamanders do not have claws, and

10212-469: The bone marrow, their subsequent circulation for around 90 days in the blood stream, and their eventual cell-death in the spleen. Another example of physiological regeneration is the sloughing and rebuilding of a functional endometrium during each menstrual cycle in females in response to varying levels of circulating estrogen and progesterone. However, humans are limited in their capacity for reparative regeneration, which occurs in response to injury. One of

10360-478: The breeding season. Cave species dwelling in darkness lack pigmentation and have a translucent pink or pearlescent appearance. Salamanders range in size from the minute salamanders , with a total length of 27 mm ( 1 + 1 ⁄ 8  in), including the tail, to the Chinese giant salamander which reaches 1.8 m (6 ft) and weighs up to 65 kg (145 lb). All the largest species are found in

10508-455: The changing of pressures within the buccal and pharyngeal cavities to ensure diffusion of oxygen onto the gill curtain, neotenic salamanders such as Necturus use specified musculature, such as the levatores arcuum, to move external gills to keep the respiratory surfaces constantly in contact with new oxygenated water. Salamanders are opportunistic predators . They are generally not restricted to specific foods, but feed on almost any organism of

10656-457: The chin which are pressed against the females' nostrils during the courtship ritual. They may function to speed up the mating process, reducing the risk of its being disrupted by a predator or rival male. The gland at the base of the tail in Plethodon cinereus is used to mark fecal pellets to proclaim territorial ownership. Olfaction in salamanders plays a role in territory maintenance,

10804-472: The cloacae of females. The results of this research may be used in captive-breeding programmes for endangered species. The order name Urodela comes from the name Urodèles given by André Marie Constant Duméril in 1805, it is derived from the Greek words οὐρά ourā́ "tail" and δῆλος dēlos "visible, conspicuous" because of their "persistent" tails. Disagreement exists among different authorities as to

10952-424: The columella (equivalent to the stapes of higher vertebrates ) which is fused to the skull, and the operculum. An opercularis muscle connects the latter to the pectoral girdle, and is kept under tension when the animal is alert. The system seems able to detect low-frequency vibrations (500–600 Hz), which may be picked up from the ground by the fore limbs and transmitted to the inner ear. These may serve to warn

11100-617: The conservation of Salamanders includes both in situ and ex situ conservation methods. There are efforts in place for certain members of the Salamander family to be conserved under a conservation breeding program (CBP) but there should be research done ahead of time to determine if the Salamander species is actually going to value from the CBP, as researchers have noted that some species of amphibians completely fail in this environment. Various conservation initiatives are being attempted around

11248-498: The control of thyroid hormones and in obligate neotenes such as the axolotl ( Ambystoma mexicanum ), the tissues are seemingly unresponsive to the hormones. In other species, the changes may not be triggered because of underactivity of the hypothalamus-pituitary-thyroid mechanism which may occur when conditions in the terrestrial environment are too inhospitable. This may be due to cold or wildly fluctuating temperatures, aridity, lack of food, lack of cover, or insufficient iodine for

11396-514: The damage. Many of the genes that are involved in the original development of tissues are reinitialized during the regenerative process. Cells in the primordia of zebrafish fins, for example, express four genes from the homeobox msx family during development and regeneration. "Strategies include the rearrangement of pre-existing tissue, the use of adult somatic stem cells and the dedifferentiation and/or transdifferentiation of cells, and more than one mode can operate in different tissues of

11544-470: The day. Within its extensive range, the habitat of the Siberian newt is wet conifer, mixed deciduous forests in the taiga and riparian grooves in the tundra and forest steppe. They can be found near ephemeral or permanent pools, wetlands, sedge meadows, off near oxbow lakes. Their breeding season occur during May or beginning of June, in pools of water. A single egg sac contains 50-80 eggs on average, with

11692-414: The de-differentiation, transformation, and re-differentation of cells to regenerate tissues. How prominent morphallactic regeneration is in oligochaetes is currently not well understood. Although relatively under-reported, it is possible that morphallaxis is a common mode of inter-segment regeneration in annelids. Following regeneration in L. variegatus , past posterior segments sometimes become anterior in

11840-533: The definition of the terms Caudata and Urodela. Some maintain that the Urodela should be restricted to the crown group , with the Caudata being used for the total group. Others restrict the name Caudata to the crown group and use Urodela for the total group. The former approach seems to be most widely adopted and is used in this article. Regeneration (biology) At its most elementary level, regeneration

11988-603: The different species of salamanders, and can involve gills, lungs, skin, and the membranes of mouth and throat. Larval salamanders breathe primarily by means of gills , which are usually external and feathery in appearance. Water is drawn in through the mouth and flows out through the gill slits. Some neotenic species such as the mudpuppy ( Necturus maculosus ) retain their gills throughout their lives, but most species lose them at metamorphosis . The embryos of some terrestrial lungless salamanders, such as Ensatina , that undergo direct development, have large gills that lie close to

12136-406: The egg's surface. When present in adult salamanders, lungs vary greatly among different species in size and structure. In aquatic, cold-water species like the torrent salamanders ( Rhyacotriton ), the lungs are very small with smooth walls, while species living in warm water with little dissolved oxygen, such as the lesser siren ( Siren intermedia ), have large lungs with convoluted surfaces. In

12284-755: The eggs are laid. In the Asiatic salamanders , the giant salamanders and Sirenidae , which are the most primitive groups, the fertilization is external. In a reproductive process similar to that of typical frogs, the male releases sperm onto the egg mass. These salamanders also have males that exhibit parental care , which otherwise only occur in females with internal fertilization. Three different types of egg deposition occur. Ambystoma and Taricha spp. spawn large numbers of small eggs in quiet ponds where many large predators are unlikely. Most dusky salamanders ( Desmognathus ) and Pacific giant salamanders ( Dicamptodon ) lay smaller batches of medium-sized eggs in

12432-437: The eggs inside her body until they hatch, either into larvae to be deposited in a water body, or into fully formed juveniles. In temperate regions, reproduction is usually seasonal and salamanders may migrate to breeding grounds. Males usually arrive first and in some instances set up territories . Typically, a larval stage follows in which the organism is fully aquatic. The tadpole has three pairs of external gills, no eyelids,

12580-530: The few species of living amphibians to occur in brackish or salt water. Many salamanders do not use vocalisations, and in most species the sexes look alike, so they use olfactory and tactile cues to identify potential mates, and sexual selection occurs. Pheromones play an important part in the process and may be produced by the abdominal gland in males and by the cloacal glands and skin in both sexes. Males are sometimes to be seen investigating potential mates with their snouts. In Old World newts, Triturus spp.,

12728-415: The final molt and metamorphosis . Beetle larvae, for example, can regenerate amputated limbs. Fruit fly larvae do not have limbs but can regenerate their appendage primordia, imaginal discs . In both systems, the regrowth of the new tissue delays pupation. Mechanisms underlying appendage limb regeneration in insects and crustaceans are highly conserved. During limb regeneration species in both taxa form

12876-481: The formation of thyroid hormones. Genetics may also play a part. The larvae of tiger salamanders ( Ambystoma tigrinum ), for example, develop limbs soon after hatching and in seasonal pools promptly undergo metamorphosis. Other larvae, especially in permanent pools and warmer climates, may not undergo metamorphosis until fully adult in size. Other populations in colder climates may not metamorphose at all, and become sexually mature while in their larval forms. Neoteny allows

13024-406: The four families giant salamanders , sirens , Congo eels and Proteidae , who are all aquatic and obligate paedomorphs. Some of the largest terrestrial salamanders, which goes through full metamorphosis, belongs to the family of Pacific giant salamanders , and are much smaller. Most salamanders are between 10 and 20 cm (4 and 8 in) in length. An adult salamander generally resembles

13172-704: The frogs and toads, within Batrachia . The oldest known total-group ( Caudata ) salamander is Triassurus from the Triassic of Kyrgyzstan . Further salamander fossils are known from the Middle Jurassic of England , Scotland , China , and Kazakhstan . The oldest known crown-group salamander ( Urodela ) remains uncertain but recent analyses suggest it is Valdotriton from the Late Jurassic of Spain . Salamanders are found only in

13320-449: The future. Skin secretions of the tiger salamander ( Ambystoma tigrinum ) fed to rats have been shown to produce aversion to the flavor, and the rats avoided the presentational medium when it was offered to them again. The fire salamander ( Salamandra salamandra ) has a ridge of large granular glands down its spine which are able to squirt a fine jet of toxic fluid at its attacker. By angling its body appropriately, it can accurately direct

13468-415: The genetic level, regeneration is fundamentally regulated by asexual cellular processes. Regeneration is different from reproduction. For example, hydra perform regeneration but reproduce by the method of budding . The regenerative process occurs in two multi-step phases: the preparation phase and the redevelopment phase. Regeneration begins with an amputation which triggers the first phase. Right after

13616-437: The ground or in the water according to species, and the female picks this up with her vent. The spermatophore has a packet of sperm supported on a conical gelatinous base, and often an elaborate courtship behavior is involved in its deposition and collection. Once inside the cloaca, the spermatozoa move to the spermatheca , one or more chambers in the roof of the cloaca, where they are stored for sometimes lengthy periods until

13764-404: The group. Examples of physiological regeneration in mammals include epithelial renewal (e.g., skin and intestinal tract), red blood cell replacement, antler regeneration and hair cycling. Male deer lose their antlers annually during the months of January to April then through regeneration are able to regrow them as an example of physiological regeneration. A deer antler is the only appendage of

13912-411: The hair cells in their cochlea following noise damage or ototoxic drug damage. Despite this evidence, contemporary studies suggest reparative regeneration in avian species is limited to periods during embryonic development. An array of molecular biology techniques have been successful in manipulating cellular pathways known to contribute to spontaneous regeneration in chick embryos. For instance, removing

14060-464: The healing process between MRL mice and other mice. Study of the regenerative process in these animals is aimed at discovering how to duplicate them in humans, such as deactivation of the p21 gene. However, recent work has shown that MRL mice actually close small ear holes with scar tissue, rather than regeneration as originally claimed. MRL mice are not protected against myocardial infarction ; heart regeneration in adult mammals ( neocardiogenesis )

14208-426: The hydra supports its efficient regenerative ability. Regeneration among hydra occurs as foot regeneration arising from the basal part of the body, and head regeneration, arising from the apical region. Regeneration tissues that are cut from the gastric region contain polarity, which allows them to distinguish between regenerating a head in the apical end and a foot in the basal end so that both regions are present in

14356-419: The immune response. Adult neurogenesis is also a form of cellular regeneration. For example, hippocampal neuron renewal occurs in normal adult humans at an annual turnover rate of 1.75% of neurons. Cardiac myocyte renewal has been found to occur in normal adult humans, and at a higher rate in adults following acute heart injury such as infarction. Even in adult myocardium following infarction, proliferation

14504-507: The injury site, and these form a wound plug. Tissue regeneration is widespread among echinoderms and has been well documented in starfish (Asteroidea) , sea cucumbers (Holothuroidea) , and sea urchins (Echinoidea). Appendage regeneration in echinoderms has been studied since at least the 19th century. In addition to appendages, some species can regenerate internal organs and parts of their central nervous system. In response to injury starfish can autotomize damaged appendages. Autotomy

14652-482: The interactive Axolotl Regenerative Telencephalon Interpretation via Spatiotemporal Transcriptomic Atlas . Anurans (frogs) can only regenerate their limbs during embryonic development. Reactive oxygen species (ROS) appear to be required for a regeneration response in the anuran larvae. ROS production is essential to activate the Wnt signaling pathway, which has been associated with regeneration in other systems. Once

14800-403: The larvae of salamanders possess these teeth. Although larval teeth are shaped like pointed cones, the teeth of adults are adapted to enable them to readily grasp prey. The crown , which has two cusps (bicuspid), is attached to a pedicel by collagenous fibers. The joint formed between the bicuspid and the pedicel is partially flexible, as it can bend inward, but not outward. When struggling prey

14948-404: The larval stage may last from days to years, depending on species. Sometimes this stage is completely bypassed, and the eggs of most lungless salamanders (Plethodontidae) develop directly into miniature versions of the adult without an intervening larval stage. By the end of the larval stage, the tadpoles already have limbs and metamorphosis takes place normally. In salamanders, this occurs over

15096-619: The larval state. The word salamander comes from Old French salamandre from Latin salamandra from Greek σαλαμάνδρα  : salamándra, of uncertain, possibly, pre-Greek origin. The Greek word is used for the fire salamander . The skin lacks scales and is moist and smooth to the touch, except in newts of the Salamandridae, which may have velvety or warty skin, wet to the touch. The skin may be drab or brightly colored, exhibiting various patterns of stripes, bars, spots, blotches, or dots. Male newts become dramatically colored during

15244-829: The last few decades of the 20th century, although no direct link between the fungus and the population decline has yet been found. The IUCN made further efforts in 2005 as they established the Amphibian Conservation Action Plan (ACAP), which was subsequently followed by Amphibian Ark (AArk), Amphibian Specialist Group (ASG), and finally the umbrella organization known as the Amphibian Survival Alliance (ASA). Researchers also cite deforestation , resulting in fragmentation of suitable habitats, and climate change as possible contributory factors. Species such as Pseudoeurycea brunnata and Pseudoeurycea goebeli that had been abundant in

15392-520: The late 1800s and was popularized by T.H. Morgan at the beginning of the 20th century. Alejandro Sanchez-Alvarado and Philip Newmark transformed planarians into a model genetic organism in the beginning of the 20th century to study the molecular mechanisms underlying regeneration in these animals. Planarians exhibit an extraordinary ability to regenerate lost body parts. For example, a planarian split lengthwise or crosswise will regenerate into two separate individuals. In one experiment, T.H. Morgan found that

15540-499: The limb skeleton has developed in frogs, regeneration does not occur ( Xenopus can grow a cartilaginous spike after amputation). The adult Xenopus laevis is used as a model organism for regenerative medicine . In 2022, a cocktail of drugs and hormones ( 1,4-DPCA , BDNF , growth hormone , resolvin D5, and retinoic acid ), in a single dose lasting 24 hours, was shown to trigger long-term leg regeneration in adult X. laevis . Instead of

15688-509: The limbs and depending on the conditions in which regeneration takes place, such as age of the animal, the inter-relationship of the injured tissue with other muscles, and the type of operation, can involve complete regeneration of some musculoskeletal structure. Werber and Goldschmidt (1909) found that the goose and duck were capable of regenerating their beaks after partial amputation and Sidorova (1962) observed liver regeneration via hypertrophy in roosters. Birds are also capable of regenerating

15836-414: The local cells dedifferentiate at the wound site into progenitor to form a blastema . Second, the blastemal cells will undergo cell proliferation , patterning, cell differentiation and tissue growth using similar genetic mechanisms that deployed during embryonic development. Ultimately, blastemal cells will generate all the cells for the new structure. After amputation, the epidermis migrates to cover

15984-738: The local population on the restoration of the natural habitat of these creatures. This proximity is a large factor that has impacted the survival of the axolotl, as the city has expanded to take over the Xochimilco region in order to make use of its resources for water and provision and sewage. It is farmed for use in research facilities and so may one day return to its natural habitat. The recent decline in population has substantially impacted genetic diversity among populations, making it difficult to further progress scientifically. Some genetic indiversity due to paedeomorphism in Ambystoma species such as

16132-410: The lungless salamanders ( family Plethodontidae and the clawed salamanders in the family of Asiatic salamanders ), no lungs or gills are present, and gas exchange mostly takes place through the skin, known as cutaneous respiration , supplemented by the tissues lining the mouth. To facilitate this, these salamanders have a dense network of blood vessels just under the skin and in the mouth. In

16280-471: The males are sexually dimorphic and display in front of the females. Visual cues are also thought to be important in some Plethodont species. Except for terrestrial species in the three families Plethodontidae , Ambystomatidae , and Salamandridae , salamanders mate in water. The mating varies from courtship between a single male and female to explosive group breeding. In the clade Salamandroidea , which makes up about 90% of all species, fertilization

16428-412: The middle, and each half generates a new end to form two clones of the original. Echinoderms (such as the sea star), crayfish, many reptiles, and amphibians exhibit remarkable examples of tissue regeneration. The case of autotomy , for example, serves as a defensive function as the animal detaches a limb or tail to avoid capture. After the limb or tail has been autotomized, cells move into action and

16576-451: The migration of interstitial progenitors towards the wound, cell death , phagocytosis of cell debris, and reconstruction of the extracellular matrix. Regeneration in hydra has been defined as morphallaxis, the process where regeneration results from remodeling of existing material without cellular proliferation. If a hydra is cut into two pieces, the remaining severed sections form two fully functional and independent hydra, approximately

16724-719: The molecular level in the annelid Capitella teleta . Leeches , however, appear incapable of segmental regeneration. Furthermore, their close relatives, the branchiobdellids , are also incapable of segmental regeneration. However, certain individuals, like the lumbriculids, can regenerate from only a few segments. Segmental regeneration in these animals is epimorphic and occurs through blastema formation. Segmental regeneration has been gained and lost during annelid evolution, as seen in oligochaetes , where head regeneration has been lost three separate times. Along with epimorphosis, some polychaetes like Sabella pavonina experience morphallactic regeneration. Morphallaxis involves

16872-762: The molecular mechanisms that control regeneration, especially gut and germline regeneration. In these tissues, resident stem cells continually renew lost cells. The Hippo signaling pathway was discovered in flies and was found to be required for midgut regeneration. Later, this conserved signaling pathway was also found to be essential for regeneration of many mammalian tissues, including heart, liver, skin, and lung, and intestine. Many annelids (segmented worms) are capable of regeneration. For example, Chaetopterus variopedatus and Branchiomma nigromaculata can regenerate both anterior and posterior body parts after latitudinal bisection. The relationship between somatic and germline stem cell regeneration has been studied at

17020-408: The most studied regenerative responses in humans is the hypertrophy of the liver following liver injury. For example, the original mass of the liver is re-established in direct proportion to the amount of liver removed following partial hepatectomy, which indicates that signals from the body regulate liver mass precisely, both positively and negatively, until the desired mass is reached. This response

17168-515: The mudpuppy (Necturus) and some other species, and the Pacific giant salamanders and a few others have a large larynx and bands known as plicae vocales. The California giant salamander can produce a bark or rattle, and a few species can squeak by contracting muscles in the throat. The arboreal salamander can squeak using a different mechanism; it retracts its eyes into its head, forcing air out of its mouth. The ensatina salamander occasionally makes

17316-417: The nail bed (especially in children) and rib regeneration, which occurs following osteotomy for scoliosis treatment (though usually regeneration is only partial and may take up to one year). Yet another example of regeneration in humans is vas deferens regeneration, which occurs after a vasectomy and which results in vasectomy failure. The ability and degree of regeneration in reptiles differs among

17464-421: The new body orientation, consistent with morphallaxis. Following amputation, most annelids are capable of sealing their body via rapid muscular contraction. Constriction of body muscle can lead to infection prevention. In certain species, such as Limnodrilus , autolysis can be seen within hours after amputation in the ectoderm and mesoderm . Amputation is also thought to cause a large migration of cells to

17612-505: The newly regenerated organism. Head regeneration requires complex reconstruction of the area, while foot regeneration is much simpler, similar to tissue repair. In both foot and head regeneration, however, there are two distinct molecular cascades that occur once the tissue is wounded: early injury response and a subsequent, signal-driven pathway of the regenerating tissue that leads to cellular differentiation . This early-injury response includes epithelial cell stretching for wound closure,

17760-655: The opportunity to investigate the mechanisms of important biological properties, such as limb regeneration, in the axolotl. The Ambystoma Genetic Stock Center (AGSC) is a self-sustaining, breeding colony of the axolotl supported by the National Science Foundation as a Living Stock Collection. Located at the University of Kentucky, the AGSC is dedicated to supplying genetically well-characterized axolotl embryos, larvae, and adults to laboratories throughout

17908-543: The palatable yellow-eyed salamander ( Ensatina eschscholtzii ) closely resembles the toxic California newt ( Taricha torosa ) and the rough-skinned newt ( Taricha granulosa ), whereas in other parts of its range, it is cryptically colored. A correlation exists between the toxicity of Californian salamander species and diurnal habits: relatively harmless species like the California slender salamander ( Batrachoseps attenuatus ) are nocturnal and are eaten by snakes, while

18056-600: The physiological regeneration of hair in mammals, birds can regenerate their feathers in order to repair damaged feathers or to attract mates with their plumage. Typically, seasonal changes that are associated with breeding seasons will prompt a hormonal signal for birds to begin regenerating feathers. This has been experimentally induced using thyroid hormones in the Rhode Island Red Fowls. Mammals are capable of cellular and physiological regeneration, but have generally poor reparative regenerative ability across

18204-579: The prey, which is then swallowed. Though frequently feeding on slow-moving animals like snails , shrimps and worms , sirenids are unique among salamanders for having developed herbivory speciations, such as beak-like jaw ends and extensive intestines. They feed on algae and other soft-plants in the wild, and easily eat offered lettuce . Salamanders have thin skins and soft bodies, move rather slowly and might appear vulnerable to opportunistic predation, but have several effective lines of defense. Mucus coating on damp skin makes them difficult to grasp, and

18352-488: The rear. The hind limbs are extracted and push the skin farther back, before it is eventually freed by friction as the salamander moves forward with the tail pressed against the ground. The animal often then eats the resulting sloughed skin. Glands in the skin discharge mucus which keeps the skin moist, an important factor in skin respiration and thermoregulation. The sticky layer helps protect against bacterial infections and molds, reduces friction when swimming, and makes

18500-410: The recognition of predators, and courtship rituals, but is probably secondary to sight during prey selection and feeding. Salamanders have two types of sensory areas that respond to the chemistry of the environment. Olfactory epithelium in the nasal cavity picks up airborne and aquatic odors, while adjoining vomeronasal organs detect nonvolatile chemical cues, such as tastes in the mouth. In plethodonts,

18648-855: The regenerated limb, and reestablish the connections that were present prior to amputation. The time that this entire process takes varies according to the age of the animal, ranging from about a month to around three months in the adult and then the limb becomes fully functional. Researchers at Australian Regenerative Medicine Institute at Monash University have published that when macrophages , which eat up material debris, were removed, salamanders lost their ability to regenerate and formed scarred tissue instead. The axolotl salamander Ambystoma mexicanum , an organism with exceptional limb regenerative capabilities, likely undergoes epigenetic alterations in its blastema cells that enhance expression of genes involved in limb regeneration. The Axolotl has very little blood and has an excess of epidermal cells. This allows

18796-797: The regeneration process. This should not be confused with the transdifferentiation of cells which is when they lose their tissue-specific characteristics during the regeneration process, and then re-differentiate to a different kind of cell. Many arthropods can regenerate limbs and other appendages following either injury or autotomy . Regeneration capacity is constrained by the developmental stage and ability to molt. Crustaceans , which continually molt, can regenerate throughout their lifetimes. While molting cycles are generally hormonally regulated, limb amputation induces premature molting. Hemimetabolous insects such as crickets can regenerate limbs as nymphs, before their final molt. Holometabolous insects can regenerate appendages as larvae prior to

18944-466: The regeneration therapy approach of Robert O. Becker , using electrical stimulation, has shown promising results for rats and mammals in general. Some researchers have also claimed that the MRL mouse strain exhibits enhanced regenerative abilities. Work comparing the differential gene expression of scarless healing MRL mice and a poorly-healing C57BL/6 mouse strain, identified 36 genes differentiating

19092-480: The salamander family. Research is being done on the environmental cues that have to be replicated before captive animals can be persuaded to breed. Common species such as the tiger salamander and the mudpuppy are being given hormones to stimulate the production of sperm and eggs, and the role of arginine vasotocin in courtship behaviour is being investigated. Another line of research is artificial insemination , either in vitro or by inserting spermatophores into

19240-560: The same animal. All these strategies result in the re-establishment of appropriate tissue polarity, structure and form." During the developmental process, genes are activated that serve to modify the properties of cell as they differentiate into different tissues. Development and regeneration involves the coordination and organization of populations cells into a blastema , which is "a mound of stem cells from which regeneration begins". Dedifferentiation of cells means that they lose their tissue-specific characteristics as tissues remodel during

19388-434: The same purpose they originally filled meaning skin cells again become skin cells and muscle cells become muscles. These de-differentiated cells divide until enough cells are available at which point they differentiate again and the shape of the blastema begins to flatten out. It is at this point that the second phase begins, the redevelopment of the limb. In this stage, genes signal to the cells to differentiate themselves and

19536-409: The same size as the two smaller severed sections. This occurs through the exchange and rearrangement of soft tissues without the formation of new material. During Hydra head regeneration there are coordinated gene expression and chromatin regulation changes. An enhancer is a short DNA sequence (50–1500 base pairs) that can be bound by transcription factors to increase the transcription of

19684-448: The sensory epithelium of the vomeronasal organs extends to the nasolabial grooves , which stretch from the nostrils to the corners of the mouth. These extended areas seem to be associated with the identification of prey items, the recognition of conspecifics , and the identification of individuals. The eyes of most salamanders are adapted primarily for vision at night. In some permanently aquatic species, they are reduced in size and have

19832-462: The shape of the foot varies according to the animal's habitat. Climbing species have elongated, square-tipped toes, while rock-dwellers have larger feet with short, blunt toes. The tree-climbing salamander ( Bolitoglossa sp.) has plate-like webbed feet which adhere to smooth surfaces by suction, while the rock-climbing Hydromantes species from California have feet with fleshy webs and short digits and use their tails as an extra limb. When ascending,

19980-429: The slimy coating may have an offensive taste or be toxic. When attacked by a predator, a salamander may position itself to make the main poison glands face the aggressor. Often, these are on the tail, which may be waggled or turned up and arched over the animal's back. The sacrifice of the tail may be a worthwhile strategy, if the salamander escapes with its life and the predator learns to avoid that species of salamander in

20128-458: The species to survive even when the terrestrial environment is too harsh for the adults to thrive on land. A general decline in living amphibian species has been linked with the fungal disease chytridiomycosis . A higher proportion of salamander species than of frogs or caecilians are in one of the at-risk categories established by the IUCN . Salamanders showed a significant diminution in numbers in

20276-432: The spermatophores from the male axolotl. It is a safe and non-invasive method that requires the collection of the spermatophores and places them into a deep freeze for preservation. Most importantly, they have found that there is only limited damage done to the spermatophores upon thawing and thus it is a viable option. As of 2013, it is a method that is being used to save not only the axolotl but also numerous other members of

20424-439: The spray for a distance of up to 80 cm (30 in). The Iberian ribbed newt ( Pleurodeles waltl ) has another method of deterring aggressors. Its skin exudes a poisonous, viscous fluid and at the same time, the newt rotates its sharply pointed ribs through an angle between 27 and 92°, and adopts an inflated posture. This action causes the ribs to puncture the body wall, each rib protruding through an orange wart arranged in

20572-449: The stump in 1–2 hours, forming a structure called the wound epithelium (WE). Epidermal cells continue to migrate over the WE, resulting in a thickened, specialized signaling center called the apical epithelial cap (AEC). Over the next several days there are changes in the underlying stump tissues that result in the formation of a blastema (a mass of dedifferentiated proliferating cells). As

20720-406: The tail props up the rear of the body, while one hind foot moves forward and then swings to the other side to provide support as the other hind foot advances. In larvae and aquatic salamanders, the tail is laterally flattened, has dorsal and ventral fins, and undulates from side to side to propel the animal through the water. In the families Ambystomatidae and Salamandridae, the male's tail, which

20868-413: The throat, assisted by depression of the eyeballs into the roof of the mouth. Many lungless salamanders of the family Plethodontidae have more elaborate feeding methods. Muscles surrounding the hyoid bone contract to store elastic energy in springy connective tissue, and actually "shoot" the hyoid bone out of the mouth, thus elongating the tongue. Muscles that originate in the pelvic region and insert in

21016-502: The tissues will regenerate. In some cases a shed limb can itself regenerate a new individual. Limited regeneration of limbs occurs in most fishes and salamanders, and tail regeneration takes place in larval frogs and toads (but not adults). The whole limb of a salamander or a triton will grow repeatedly after amputation. In reptiles, chelonians, crocodilians and snakes are unable to regenerate lost parts, but many (not all) kinds of lizards, geckos and iguanas possess regeneration capacity in

21164-431: The tongue are used to reel the tongue and the hyoid back to their original positions. An aquatic salamander lacks muscles in the tongue, and captures its prey in an entirely different manner. It grabs the food item, grasps it with its teeth, and adopts a kind of inertial feeding. This involves tossing its head about, drawing water sharply in and out of its mouth, and snapping its jaws, all of which tend to tear and macerate

21312-487: The tongue bulges and changes shape as it shoots forward. The protruded tongue has a central depression, and the rim of this collapses inward as the target is struck, trapping the prey in a mucus-laden trough. Here it is held while the animal's neck is flexed, the tongue retracted and jaws closed. Large or resistant prey is retained by the teeth while repeated protrusions and retractions of the tongue draw it in. Swallowing involves alternate contraction and relaxation of muscles in

21460-527: The various parts of the limb are developed. The end result is a limb that looks and operates identically to the one that was lost, usually without any visual indication that the limb is newly generated. The hydra and the planarian flatworm have long served as model organisms for their highly adaptive regenerative capabilities. Once wounded, their cells become activated and restore the organs back to their pre-existing state. The Caudata ("urodeles"; salamanders and newts ), an order of tailed amphibians ,

21608-458: The various species (see ), but the most notable and well-studied occurrence is tail-regeneration in lizards . In addition to lizards, regeneration has been observed in the tails and maxillary bone of crocodiles and adult neurogenesis has also been noted. Tail regeneration has never been observed in snakes , but see. Lizards possess the highest regenerative capacity as a group. Following autotomous tail loss, epimorphic regeneration of

21756-455: The water intermittently, and others are entirely terrestrial as adults. This group of amphibians is capable of regenerating lost limbs as well as other damaged parts of their bodies. Researchers hope to reverse engineer the regenerative processes for potential human medical applications, such as brain and spinal cord injury treatment or preventing harmful scarring during heart surgery recovery. The remarkable ability of salamanders to regenerate

21904-481: The world. The Chinese giant salamander , at 1.8 m (6 ft) the largest amphibian in the world, is critically endangered , as it is collected for food and for use in traditional Chinese medicine . An environmental education programme is being undertaken to encourage sustainable management of wild populations in the Qinling Mountains and captive breeding programmes have been set up. The hellbender

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