Salamanders are a group of amphibians typically characterized by a lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All present-day salamander families are grouped together under the order Urodela. Salamander diversity is most abundant in the Northern Hemisphere and most species are found in the Holarctic ecozone, with some species present in the Neotropical zone.
Salamanders rarely 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 the water intermittently, and others are entirely terrestrial as adults. They are capable of regenerating lost limbs, as well as other damaged parts of their bodies. Researchers hope to reverse engineer the remarkable regenerative processes for potential human medical applications, such as brain and spinal cord injury treatment or preventing harmful scarring during heart surgery recovery. Members of 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 the larval state.
|Spotted salamander, Ambystoma maculatum|
|Native distribution of salamanders (in green)|
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 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 2.7 cm (1.1 in), including the tail, to the Chinese giant salamander which reaches 1.8 m (5.9 ft) and weighs up to 65 kg (143 lb). Most, however, are between 10 and 20 cm (3.9 and 7.9 in) in length.
An adult salamander generally resembles 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 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 sidewards, 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 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, 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 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 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 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 forwards through the gap to shed the skin. When the front limbs have been worked clear, a series of body ripples pushes the skin towards 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 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 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 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, 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, 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 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 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: 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 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; however, in mating system they communicate by pheromone signaling; some species can make quiet ticking or popping noises, perhaps by the opening and closing of valves in the nose. 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 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 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 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 southern torrent salamander (Rhyacotriton variegatus), 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 the terrestrial lungless salamanders (family Plethodontidae), no lungs or gills are present, and gas exchange mostly takes place through the skin, 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 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 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. However, 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 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 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 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 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 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 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 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 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 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 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 speciations towards herbivory, 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, and move rather slowly, and at first sight might appear to be vulnerable to opportunistic predation. However, they have several effective lines of defense. Mucus coating on damp skin makes them difficult to grasp, and 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 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 the spray for a distance of up to 80 cm (31 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 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 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, 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 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 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 the frogs and toads, within Batrachia. The earliest known salamander fossils have been found in geological deposits in China and Kazakhstan, dated to the middle Jurassic period around 164 million years ago.
Salamanders are found only in 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 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 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. However, possible salamander fossils have been found on the Australian sites of Riversleigh and Murgon.
There are about 655 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 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 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.
Salamanders are not vocal and in most species the sexes look alike, so they use olfactory and tactile cues to identify potential mates, and sexual selection does occur. 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., the males are sexually dimorphic and display in front of the females. Visual cues are also thought to be important in some Plethodont species.
In about 90% of all species, fertilisation is internal. The male typically deposits a spermatophore on 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 the eggs are laid. In the most primitive salamanders, such as the Asiatic salamanders and the giant salamanders, external fertilization occurs, instead. In these species, the male releases sperm onto the egg mass in a reproductive process similar to that of typical frogs.
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 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 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, 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, narrower fins and no balancers, but instead have hind limbs already developed when they hatch. The tadpoles are carnivorous and 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 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 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 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 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 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 the cloud forests of Guatemala and Mexico during the 1970s were found by 2009 to be rare. However, 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 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 it is important to note that 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 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 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 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 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. However, there are a number of factors that work against their preservation and conservation methods. The most profound factors are that the waters in which they are endemic are severely polluted and that even if they were found in the wild again they would be fished up for either research or exotic animal sells on the black market. Another detrimental factor is that the axolotl lost their role as 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 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. However, the axolotl has the benefit of being raised in farms for the purpose of research facilities. So there is still a chance that they may be able to return to their natural habitat. The recent decline in population has substantially impacted genetic diversity among populations of axolotl, making it difficult to further progress scientifically. It is important to note that although there is a level of limited genetic diversity due to Ambystoma populations, such as the axolotl, being paedeomorphic species, it does not account for the overall lack of diversity. There is evidence that points towards a historical bottlenecking of Ambystoma that contributes to the variation issues. Unfortunately, there is no large genetic pool for the species to pull from unlike in historical times.Thus there is severe 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 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 in 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 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 the cloacae of females. The results of this research may be used in captive-breeding programmes for endangered species.
Disagreement exists between different authorities as to 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.
The 10 families belonging to Urodela are divided into three suborders. The clade Neocaudata is often used to separate the Cryptobranchoidea and Salamandroidea from the Sirenoidea.
|Cryptobranchoidea (Giant salamanders)|
|Family||Common names||Example species||
|Cryptobranchidae||Giant salamanders||Hellbender (Cryptobranchus alleganiensis)|
|Hynobiidae||Asiatic salamanders||Hida salamander (Hynobius kimurae)|
|Salamandroidea (Advanced salamanders)|
|Ambystomatidae||Mole salamanders||Marbled salamander (Ambystoma opacum)|
|Amphiumidae||Amphiumas or Congo eels||Two-toed amphiuma (Amphiuma means)|
|Dicamptodontidae||Pacific giant salamanders||Pacific giant salamander (Dicamptodon tenebrosus)|
|Plethodontidae||Lungless salamanders||Red-backed salamander (Plethodon cinereus)|
|Proteidae||Mudpuppies and olms||Olm (Proteus anguinus)|
|Rhyacotritonidae||Torrent salamanders||Southern torrent salamander (Rhyacotriton variegatus)|
|Salamandridae||Newts and true salamanders||Alpine newt (Ichthyosaura alpestris)|
|Sirenidae||Sirens||Greater siren (Siren lacertina)|
The origins and evolutionary relationships between the three main groups of amphibians (gymnophionans, urodeles and anurans) is a matter of debate. A 2005 molecular phylogeny, based on rDNA analysis, suggested that the first divergence between these three groups took place soon after they had branched from the lobe-finned fish in the Devonian (around 360 million years ago), and before the breakup of the supercontinent Pangaea. The briefness of this period, and the speed at which radiation took place, may help to account for the relative scarcity of amphibian fossils that appear to be closely related to lissamphibians. However, more recent studies have generally found more recent (Late Carboniferous to Permian) age for the basalmost divergence among lissamphibians.
The first known fossil salamanders are Kokartus honorarius from the Middle Jurassic of Kyrgyzstan and two species of the apparently neotenic, aquatic Marmorerpeton from England of a similar date. They looked superficially like robust modern salamanders but lacked a number of anatomical features that developed later. Karaurus sharovi from the Upper Jurassic of Kazakhstan resembled modern mole salamanders in morphology and probably had a similar burrowing lifestyle.
The two main groups of extant salamanders are the Cryptobranchoidea (primitive salamanders) and the Salamandroidea (advanced salamanders), also known as Diadectosalamandroidei, both seem to have appeared before the end of the Jurassic, the former being exemplified by Chunerpeton tianyiensis, Pangerpeton sinensis, Jeholotriton paradoxus, Regalerpeton weichangensis, Liaoxitriton daohugouensis and Iridotriton hechti, and the latter by Beiyanerpeton jianpingensis. By the Upper Cretaceous, most or all of the living salamander families had probably appeared.
The following cladogram shows the relationships between salamander families based on the molecular analysis of Pyron and Wiens (2011). The position of the Sirenidae is disputed, but the position as sister to the Salamandroidea best fits with the molecular and fossil evidence.
Salamanders are characteristic for their gigantic genomes, spanning the range from 14 Gb to 120 Gb (the human genome is 3.2 Gb long). The genomes of Pleurodeles waltl (20 Gb) and Ambystoma mexicanum (32 Gb) have been sequenced.
Legends have developed around the salamander over the centuries, many related to fire. This connection likely originates from the tendency of many salamanders to dwell inside rotting logs. When placed into a fire, the salamander would attempt to escape from the log, lending to the belief that salamanders were created from flames. The mythical ruler Prester John supposedly had a robe made from salamander hair; the "Emperor of India" possessed a suit made from a thousand skins; Pope Alexander III had a tunic which he valued highly and William Caxton (1481) wrote: "This Salemandre berithe wulle, of which is made cloth and gyrdles that may not brenne in the fyre." The salamander was said to be so toxic that by twining around a tree, it could poison the fruit and so kill any who ate them and by falling into a well, could kill all who drank from it.
The association of the salamander with fire appeared first in Ancient Greece, where Pliny the Elder writes in his Natural History that "A salamander is so cold that it puts out fire on contact. It vomits from its mouth a milky liquid; if this liquid touches any part of the human body it causes all the hair to fall off, and the skin to change color and break out in a rash." The ability to put out fire is repeated by Saint Augustine in the fifth century and Isidore of Seville in the seventh century.
The Japanese giant salamander has been the subject of legend and artwork in Japan, in the ukiyo-e work by Utagawa Kuniyoshi. The well-known Japanese mythological creature known as the kappa may be inspired by this salamander.
Salamanders' limb regeneration has long been the focus of interest among scientists. Researchers have been trying to find out the conditions required for the growth of new limbs and hope that such regeneration could be replicated in humans using stem cells. Axolotls have been used in research and have been genetically engineered so that a fluorescent protein is present in cells in the leg, enabling the cell division process to be tracked under the microscope. It seems that after the loss of a limb, cells draw together to form a clump known as a blastema. This superficially appears undifferentiated, but cells that originated in the skin later develop into new skin, muscle cells into new muscle and cartilage cells into new cartilage. It is only the cells from just beneath the surface of the skin that are pluripotent and able to develop into any type of cell. Researchers from the Australian Regenerative Medicine Institute have found that when macrophages were removed, salamanders lost their ability to regenerate and instead formed scar tissue. If the processes involved in forming new tissue can be reverse engineered into humans, it may be possible to heal injuries of the spinal cord or brain, repair damaged organs and reduce scarring and fibrosis after surgery.
A 1995 article in the Slovenian weekly magazine Mladina publicized Salamander brandy, a liquor supposedly indigenous to Slovenia. It was said to combine hallucinogenic with aphrodisiac effects and is made by putting several live salamanders in a barrel of fermenting fruit. Stimulated by the alcohol, they secrete toxic mucus in defense and eventually die. Besides causing hallucinations, the neurotoxins present in the brew were said to cause extreme sexual arousal.
Later research by Slovenian anthropologist Miha Kozorog (University of Ljubljana) paints a very different picture — Salamander in brandy appears to have been traditionally seen as an adulterant, one which caused ill health. It was also used as a term of slander.
Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. Modern amphibians are all Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in recent decades there has been a dramatic decline in amphibian populations for many species around the globe.
The earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land. They diversified and became dominant during the Carboniferous and Permian periods, but were later displaced by reptiles and other vertebrates. Over time, amphibians shrank in size and decreased in diversity, leaving only the modern subclass Lissamphibia.
The three modern orders of amphibians are Anura (the frogs and toads), Urodela (the salamanders), and Apoda (the caecilians). The number of known amphibian species is approximately 8,000, of which nearly 90% are frogs. The smallest amphibian (and vertebrate) in the world is a frog from New Guinea (Paedophryne amauensis) with a length of just 7.7 mm (0.30 in). The largest living amphibian is the 1.8 m (5 ft 11 in) Chinese giant salamander (Andrias davidianus), but this is dwarfed by the extinct 9 m (30 ft) Prionosuchus from the middle Permian of Brazil. The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology.Asiatic salamander
The Asiatic salamanders (family Hynobiidae) are primitive salamanders found all over Asia, and in European Russia. They are closely related to the giant salamanders (family Cryptobranchidae), with which they form the suborder Cryptobranchoidea. About half of hynobiids currently described are unique to Japan.Hynobiid salamanders practice external fertilization, or spawning. And, unlike other salamander families which reproduce internally, male hynobiids focus on egg sacs rather than females during breeding. The female lays two egg sacs at a time, each containing up to 70 eggs. Parental care is common.A few species have very reduced lungs, or no lungs at all. Larvae can sometimes have reduced external gills if they live in cold and very oxygen-rich water.Axolotl
The axolotl (, from Classical Nahuatl: āxōlōtl [aːˈʃoːloːtɬ] (listen); plural axolotls or rarely axolomeh), Ambystoma mexicanum, also known as the Mexican walking fish, is a neotenic salamander related to the tiger salamander. Although the axolotl is colloquially known as a "walking fish", it is not a fish, but an amphibian. The species was originally found in several lakes, such as Lake Xochimilco underlying Mexico City. Axolotls are unusual among amphibians in that they reach adulthood without undergoing metamorphosis. Instead of developing lungs and taking to the land, adults remain aquatic and gilled.
Axolotls should not be confused with waterdogs, the larval stage of the closely related tiger salamanders (A. tigrinum and A. mavortium), which are widespread in much of North America and occasionally become neotenic. Neither should they be confused with mudpuppies (Necturus spp.), fully aquatic salamanders that are not closely related to the axolotl but bear a superficial resemblance.As of 2010, wild axolotls were near extinction due to urbanization in Mexico City and consequent water pollution, as well as the introduction of invasive species such as tilapia and perch. They are currently listed by CITES as an endangered species and by IUCN as critically endangered in the wild, with a decreasing population. Axolotls are used extensively in scientific research due to their ability to regenerate limbs. Axolotls were also sold as food in Mexican markets and were a staple in the Aztec diet.Surveys in 1998, 2003, and 2008 found 6,000, 1,000, and 100 axolotls per square kilometer in its Lake Xochimilco habitat, respectively. A four-month-long search in 2013, however, turned up no surviving individuals in the wild. Just a month later, two wild ones were spotted in a network of canals leading from Xochimilco. The city is currently working on conserving axolotls by building "axolotl shelters" and conserving remaining and potential habitats for the salamanders.Chinese giant salamander
The Chinese giant salamander (Andrias davidianus) is the largest salamander and largest amphibian in the world, reaching a length of 1.8 m (5.9 ft), although it rarely reaches that size today. It is fully aquatic and is endemic to rocky mountain streams and lakes in China. It has been introduced to Kyoto Prefecture in Japan and Taiwan. It is considered critically endangered in the wild due to habitat loss, pollution, and overcollection, as it is considered a delicacy and used in traditional Chinese medicine. On farms in central China, it is extensively farmed and sometimes bred, although many of the salamanders on the farms are caught in the wild. It has been listed as one of the top-10 "focal species" in 2008 by the Evolutionarily Distinct and Globally Endangered project. The Chinese giant salamander is considered to be a "living fossil". Although protected under Chinese law and CITES Appendix I, the wild population has declined by more than an estimated 80% since the 1950s. Although traditionally recognized as one of two living species of Andrias salamander in Asia, the other being the Japanese giant salamander, evidence indicates that the Chinese giant salamander may be composed of at least five cryptic species, further compounding each individual species' endangerment.Fire salamander
The fire salamander (Salamandra salamandra) is possibly the best-known salamander species in Europe.
It is black with yellow spots or stripes to a varying degree; some specimens can be nearly completely black while on others the yellow is dominant. Shades of red and orange may sometimes appear, either replacing or mixing with the yellow according to subspecies. Fire salamanders can have a very long lifespan; one specimen lived for more than 50 years in Museum Koenig, a German natural history museum.Giant salamander
The Cryptobranchidae are a family of fully aquatic salamanders commonly known as the giant salamanders. A single species, the hellbender (Cryptobranchus alleganiensis) occurs in the eastern United States, while Asian species occur in China and Japan. They are the largest living amphibians known today. The Japanese giant salamander (Andrias japonicus) reaches up to 1.44 m (4.7 ft) in length, feeds at night on fish and crustaceans, and has been known to live for more than 50 years in captivity. The Chinese giant salamander (Andrias davidianus) can reach a length of 1.8 m (5.9 ft).Grilling
Grilling is a form of cooking that involves dry heat applied to the surface of food, commonly from above, below or from the side. Grilling usually involves a significant amount of direct, radiant heat, and tends to be used for cooking meat and vegetables quickly. Food to be grilled is cooked on a grill (an open wire grid such as a gridiron with a heat source above or below), using a cast iron/frying pan, or a grill pan (similar to a frying pan, but with raised ridges to mimic the wires of an open grill).
Heat transfer to the food when using a grill is primarily through thermal radiation. Heat transfer when using a grill pan or griddle is by direct conduction. In the United States, when the heat source for grilling comes from above, grilling is called broiling. In this case, the pan that holds the food is called a broiler pan, and heat transfer is through thermal radiation.
Direct heat grilling can expose food to temperatures often in excess of 260 °C (500 °F). Grilled meat acquires a distinctive roast aroma and flavor from a chemical process called the Maillard reaction. The Maillard reaction only occurs when foods reach temperatures in excess of 155 °C (310 °F).Studies have shown that cooking beef, pork, poultry, and fish at high temperatures can lead to the formation of heterocyclic amines, benzopyrenes, and polycyclic aromatic hydrocarbons, which are carcinogens.Marination may reduce the formation of these compounds. Grilling is often presented as a healthy alternative to cooking with oils, although the fat and juices lost by grilling can contribute to drier food.Heinkel He 162
The Heinkel He 162 Volksjäger (German, "People's Fighter"), the name of a project of the Emergency Fighter Program design competition, was a German single-engine, jet-powered fighter aircraft fielded by the Luftwaffe in World War II. It was designed and built quickly and made primarily of wood as metals were in very short supply and prioritised for other aircraft. Volksjäger was the Reich Air Ministry's official name for the government design program competition won by the He 162 design. Other names given to the plane include Salamander, which was the codename of its construction program, and Spatz ("Sparrow"), which was the name given to the plane by Heinkel.List of amphibians of Alabama
The U.S. state of Alabama has 73 known indigenous amphibian species. These indigenous species include 30 frog and toad species and 43 salamander species. Two of these native species may have become extirpated within the state. They are the Mississippi gopher frog and flatwoods salamander.Human predation, pollution, and habitat destruction has placed several amphibian species at risk of extirpation or extinction. The Alabama Department of Conservation and Natural Resources lists the conservation status of each species within the state with a rank of lowest, low, moderate, high, and highest concern.Mole salamander
The mole salamanders (genus Ambystoma) are a group of advanced salamanders endemic to North America, the only genus in the family Ambystomatidae. The group has become famous due to the presence of the axolotl (A. mexicanum), widely used in research due to its paedomorphosis, and the tiger salamander (A. tigrinum, A. mavortium) which is the official amphibian of many states, and often sold as a pet.Pavilion Books
Pavilion Books Holdings Ltd is an English publishing company based in London.
It specialises in illustrated books and digital content.Plethodontidae
The Plethodontidae, or lungless salamanders, are a family of salamanders. Most species are native to the Western Hemisphere, from British Columbia to Brazil, although a few species are found in Sardinia, Europe south of the Alps, and South Korea. In terms of number of species, they are by far the largest group of salamanders.Salamander (video game)
Salamander (沙羅曼蛇 (サラマンダ), Saramanda), retitled Life Force (ライフフォース, Raifu Fōsu) in North America and in the Japanese arcade re-release, in Europe known as Life Force: Salamander, is a scrolling shooter arcade game by Konami. Released in 1986 as a spin-off of Gradius, Salamander introduced a simplified power-up system, two-player cooperative gameplay and both horizontally and vertically scrolling stages. Some of these later became the norm for future Gradius games.
Salamander was followed with a sequel in 1996 titled Salamander 2.Salamander letter
The salamander letter is a document about the history of the Latter-day Saint movement.
The letter was one of hundreds of documents concerning the history of LDS movement that surfaced in the early 1980s. The salamander letter presented a view of Latter-day Saint founder Joseph Smith's life that stood sharply at odds with the commonly accepted version of the early progression of the church Smith established.
Initially accepted by some document experts and collectors, and rejected by others, the salamander letter generated much discussion and debate inside and outside the Latter-day Saint movement. Kenneth W. Rendell lent credence to it by stating that the ink, paper and postmark were all consistent with the period; he concluded that "there is no indication that the document is a forgery." The document was later demonstrated to be a forgery created by Hofmann, who had been responsible for the "discovery" of many other notable documents. Rendell then recast his conclusion, stating that while there was "the absence of any indication of forgery in the letter itself, there was also no evidence that it was genuine."Salamander shark
The salamander shark or salamander catshark (Parmaturus pilosus) is a little known catshark that inhabits a range from Japan and the East China Sea, on the upper to middle continental slope at depths of 358–895 m. Specimens of this species can attain a total length of at least 64 cm. This catshark is a potential bycatch of trawl fisheries operating within its range, but no details are available. There are high levels of squalene in this catshark's liver. The reproduction of this catshark is oviparous.Salamanders in folklore
The salamander is an amphibian of the order Urodela which, as with many real creatures, often has been ascribed fantastic and sometimes occult qualities by pre-modern authors (as in the allegorical descriptions of animals in medieval bestiaries) not possessed by the real organism. The legendary salamander is often depicted as a typical salamander in shape, with a lizard-like form, but is usually ascribed an affinity with fire, sometimes specifically elemental fire.Salamandridae
Salamandridae is a family of salamanders consisting of true salamanders and newts. Currently, 74 species (with more expected) have been identified in the Northern Hemisphere - Europe, Asia, the northern tip of Africa, and North America. Salamandrids are distinguished from other salamanders by the lack of rib or costal grooves along the sides of their bodies and by their rough skin. Their skin is very granular because of the number of poison glands. They also lack nasolabial grooves.
With a few exceptions, salamandrids have patterns of bright and contrasting colours, most of these are to warn potential predators of their toxicity. They have four well-developed limbs, with four toes on the fore limbs, and (in most cases) five toes on the hind limbs. They vary from 7 to 30 cm (3 to 12 in) in length.All species within the genus Lyciasalamandra are viviparous, meaning they give birth to live young, without a tadpole stage. There are some species within the genus Salamandra are known to be viviparous too. Some newts are neotenic, being able to reproduce before they are fully metamorphosed.Spotted salamander
The spotted salamander or yellow-spotted salamander (Ambystoma maculatum) is a mole salamander common in the eastern United States and Canada. The spotted salamander is the state amphibian of Ohio and South Carolina. This salamander ranges from Nova Scotia, to Lake Superior, to southern Georgia and Texas. Its embryos have been found to have symbiotic algae living inside them, the only known example of vertebrate cells hosting an endosymbiont microbe.Tiger salamander
The tiger salamander (Ambystoma tigrinum) is a North American species of mole salamander.
Extant amphibian positions by subclass
Caudate families by suborder