Definitions

salamander

salamander

[sal-uh-man-der]
salamander, an amphibian of the order Urodela, or Caudata. Salamanders have tails and small, weak limbs; superficially they resemble the unrelated lizards (which are reptiles), but they are easily distinguished by their lack of scales and claws, and by their moist, usually smooth skins. Salamanders are found in damp regions of the northern temperate zone and are most abundant in North America. Most are under 6 in. (15 cm) long, but the giant salamander of Japan (Megalobatrachus japonicus) may reach a length of over 5 ft (1.5 m). Most salamanders are terrestrial as adults, living near water or in wet vegetation, but some are aquatic and a few are arboreal, burrowing, or cave-dwelling. Most are nocturnal, and all avoid direct light. Salamanders are able to regenerate a lost limb or tail. They feed on small animals, such as insects, worms, and snails.

Most salamanders breed in water and are gregarious at breeding time, when there is usually a courtship display. In most species fertilization is internal. The male deposits sperm packets, which the female picks up with the cloaca; the sperm is then stored until fertilization takes place. The eggs, surrounded by gelatinous material, are usually laid in ponds or brooks, where they develop into aquatic larvae that can breathe by means of gills. A few salamanders breed on land, laying their eggs under rotting vegetation; the young pass through the gilled stage in the egg, emerging as miniature adults. Such strictly terrestrial forms are the red-backed salamander (Plethodon cinereus) and slimy salamander (P. glutinosus) of E United States and the slender salamander (Batrachoseps attenuatus) of the Pacific coast.

Most salamanders, including most that remain in an aquatic environment, go through a typical amphibian metamorphosis into air-breathing adults. Generally the adults have lungs, but in the large family of lungless salamanders (Plethodontidae) breathing occurs entirely through the skin and the lining of the throat. In a few salamanders growth occurs without metamorphosis, and the gilled, juvenile form is able to reproduce. This phenomenon (called neoteny) is found in the sirens (family Sirenidae) of S United States and N Mexico, in the mud puppies (family Protidae), and in the Mexican axolotl. It may also occur in the Western varieties of the North American tiger salamander (Ambystoma tigrinum) under certain environmental conditions. The newts are a large, widely distributed family of salamanders; North American species include the red-spotted newt, which goes through a terrestrial stage known as the red eft.

The North American blind salamanders (several genera in the family Plethodontidae) live in underground streams, caves, and wells in S United States. As adults they have whitish, translucent skin, which covers their eyes. The olm is a European blind salamander related to the mud puppy. The giant salamander (Dicamptodon ensatus) of the NW United States grows to 12 in. (30 cm) in length. The hellbender (Cryptobranchus alleganiensis) of E United States and the so-called Congo eel (Amphiuma means) are large aquatic species. The former, of the same family as the Japanese giant salamander, grows to 20 in. (50 cm); the latter, slender and eellike in appearance, with tiny legs, may reach 30 in. (75 cm).

Classification

There are over 200 salamander species, classified in approximately 60 genera and 8 families of the phylum Chordata, subphylum Vertebrata, class Amphibia, order Urodela.

Salamander (Salamandra terrestris)

Any member of about 400 species in 10 amphibian families (order Caudata), commonly found in fresh water and damp woodlands, principally in temperate regions of the Northern Hemisphere. Salamanders are generally nocturnal, short-bodied, 4–6 in. (10–15 cm) long, and brightly coloured. They have a tail, two pairs of limbs of roughly the same size, moist, smooth skin, teeth on the jaws and roof of the mouth, and, usually, internal fertilization. The largest species, the Chinese giant salamander (Andrias davidianus), is 5 ft (1.5 m) long. Salamanders eat insects, worms, snails, and other small animals, including members of their own species. Seealso hellbender; newt.

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Salamander (orig. from Persian: sām, "fire", and andarūn, "within") is the common name for a group of approximately 500 species of amphibians. Typically characterized by slender bodies, short noses, and long tails. All known fossil and extant species comprise the order Caudata, while sometimes extant are distinctly called Urodela. Salamanders have four front toes and their hind legs have five. Their moist skin usually makes them reliant on habitats in or near water, or under some protection (e.g., moist ground), often in a wetland. Some salamander species are fully aquatic throughout life, some take to the water intermittently, and some are entirely terrestrial as adults. All species lay eggs in water. Uniquely among vertebrates, they are capable of regenerating lost limbs, as well as other body parts.

Description

Many caudates are relatively small, but there are definite exceptions. North America hosts the hellbender, the eastern tiger salamander, and the mudpuppy which can reach the length of or more. In Japan and China the giant salamander is found, which reaches and weighs up to .

Respiration differs among the different species of salamanders. In those that lack lungs, respiration is done through gills as water passes over the gill slits. Some salamanders that are terrestrial have lungs that are used in respiration similar to that in mammals. However, some terrestrial species lack both lungs and gills and perform gas exchange through their skin, a process known as valarian respiration in which the capillary beds are spread throughout the epidermis, including inside the mouth.

Hunting is yet another unique aspect of salamanders. Muscles surrounding the hyoid bone contract to create pressure and actually "shoot" the hyoid bone out of the mouth along with the tongue. The tip of the tongue is composed of a mucus which creates a sticky end to which the prey is captured. Muscles in the pelvic region are used in order to reel the tongue and the hyoid back to its original position. To find their prey, salamanders use trichromatic color vision in the ultraviolet range based on three photoreceptor types maximally sensitive around , 500 nm and 570 nm.

Distribution

Salamanders split off from the other amphibians during the Mid to Late Permian, and initially were similar to modern members of the Cryptobranchoidea. Any resemblance to lizards is the result of convergence of the basic tetrapod body plan, as they are no more closely related to lizards than they are to mammals. Their nearest relatives are the frogs and toads, within Batrachia.

Caudates are found on all continents except for most of Africa, Australia and Antarctica. One-third of the known salamanders, are found in North America. The highest concentration of these is found in the Appalachian Mountains region. Species of salamander are numerous and found in most moist or arid habitats in the northern hemisphere. They usually live in or near brooks, creeks, ponds, and other moist locations.

Development

The life history of salamanders is similar to other amphibians such as frogs, toads, etc.. The life cycle begins with an egg stage, usually laid the previous winter in a pond. A larval stage follows in which the organism is fully aquatic. Depending on species, the larval stage may or may not possess legs. The salamander possesses gills at this point. Some species (such as Dunn's Salamander (Plethodon dunni)) of salamander exhibit no larval stage. Neoteny has been observed in all salamander families, in which an individual may retain gills into sexual maturity. This may be universally possible in all salamander species. More commonly, however, metamorphosis continues with the loss of gills, the growth (or increase in size) of legs, and the capability of the animal to function terrestrially. However, the species that lack hearts, lungs, or gills perform gas exchange through their skin, a process known as valarian respiration in which the capillary beds are spread throughout the epidermis, including inside the mouth.

Taxonomy

There are ten families belonging to the order Caudata, divided into three suborders. The clade Neocaudata is often used to separate Cryptobranchoidea and Salamandroidea from the Sirenoidea.
'''Cryptobranchoidea (Giant salamanders)
Family Common Names Example Species Example Photo
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 Back 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 (Triturus alpestris)
Sirenoidea (Sirens)
Sirenidae Sirens Greater Siren (Siren lacertina)

Mythology and popular culture

Numerous 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 - a belief that gave the creature its name.

Associations of the salamander with fire appear in the Talmud and the Hadith, as well as in the writings of Conrad Lycosthenes, Benvenuto Cellini, Ray Bradbury, David Weber, Paracelsus and Leonardo da Vinci.

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