The mole salamanders (genus Ambystoma) are a group of salamanders endemic to North America, the only genus in the family Ambystomatidae. The group has become famous due to the presence of the Axolotl (Ambystoma mexicanum), widely used in research, and the Tiger Salamander (Ambystoma tigrinum, Ambystoma mavortium) which is the official amphibian of many states, and often sold as a pet.Terrestial mole salamanders are identified by having wide, protruding eyes, prominent costal grooves, thick arms, and rounded tails. Most have vivid patterning on dark backgrounds, with marks ranging from deep blue spots to large yellow bars depending on the species. Terrestrial adults spend most of their life underground in burrows either of their own making or abandoned by other animals. Some Northern species may hibernate in these burrows throughout the winter. They live alone and feed on any available invertebrate. Adults spend little time in the water, only returning to the ponds of their birth to breed.
 
All mole salamanders are oviparous and lay large eggs in clumps in the water. Their fully aquatic larvae are branchiate, with 3 pairs of external gills behind their head and above their gill slits. Larvae have large caudal fins which extend from the back of their head to their tail and to their cloaca. Larvae grow limbs soon after hatching, with four toes on the forearms, and five toes on the hindlegs. Their eyes are wide-set and lack true eye-lids.
 
The larvae of some species (especially those in the South, and Tiger salamanders) can reach their adult size before undergoing metamorphosis. During metamorphosis, the gills of the larvae disappear, as does the fin. The tail, skin, and limbs become thicker, and the eyes develop lids. Their lungs become fully developed, allowing for a fully terrestrial existence.
 
The presence of neotenic populations near those with large larvae has made it difficult to identify mole salamander species. The Tiger Salamander complex used to be considered a single species ranging from Canada to Mexico, falling under the name Ambystoma tigrinum. Despite differences in coloration and larvae, Tiger Salamanders were found throughout their unbroken range, which made it difficult to delineate subspecies, let-alone elevate any populations to species status. In morphological terms, Tiger salamanders are all very similar, with large heads, small eyes, and thick bodies. This is probably because Tiger Salamanders have the primitive morphology of mole salamanders. They are also the largest of the mole salamanders, and have very large larvae. All populations have similar lifestyles and life-cycles are identical. However, when one looks at Tiger Salamander populations that were distant from each other, it becomes apparent that there are different species within this complex. The problem is that the ranges of these potential species overlap, and hybridization occurs, blurring the lines between species.
 
Several subspecies of Ambystoma tigrinum were named in order to deal with this problem. Recently, the Barred Tiger Salamander, Ambystoma mavortium, was elevated to species status – covering the Tiger salamander populations in the Western and Central United States. Several distinct subspecies still exist in Ambystoma mavortium which may be elevated to species status at some point in the future. The California Tiger Salamander,Ambystoma californiense, has also been elevated out of Ambystoma tigrinum, and is actually very distantly related to all other mole salamander species. The Mexican Tiger Salamander, Ambystoma velasci, was elevated out of Ambystoma tigrinum through genetic analysis in 1997. All accounts referring to the Axolotl as a close relative of Ambystoma tigrinum are now considered wrong, as they are now separated by both geography and many species between. Instead, it is Ambystoma velasci which shares the Axolotl's habitat, and is probably closely related to it. The Mexican Tiger Salamander was probably the parent of most of the neotenic species, which raises the possibility that Ambystoma velasci is paraphyletic, and may be broken up into more species in the future.
 
The most famous result of the tendency of mole salamander species to hybridize where they come in contact is the jeffersonianum-laterale complex of species. These two species were separated by ice age glaciation, but when the ice melted, they came into easy contact with each other and interbred. The Jefferson Salamander (jeffersonianum), and the Blue-spotted Salamander (laterale) have variously been put together as one species, and taken apart based on these hybrid populations. They are currently considered separate due to the genetic make up of isolated populations.
The hybridization of Ambystoma laterale and Ambystoma jeffersonianum has led to the development of two completely female populations of mole salamander. Both of these are polyploid, like the all-female species of Whiptail lizards. Ambystoma platineum, the Silvery Salamander, is technically a population of hybrid jeffersonianum-laterale salamanders. However, the Silvery Salamander is completely asexual and does not technically breed. Ambystoma platineum females go through mating rituals with Blue-spotted males in order to begin parthenogenesis, a process known as gynogenesis. They then lay eggs that contain only clones of the mother. Therefore all members of this populations are clonal. Silvery Salamanders may be considered a species, since there is no genetic exchange with any other salamander group, but it is usually classified within Ambystoma laterale. Genetically, they are all one Blue-Spotted-Jefferson hybrid salamander. Hybridization has also given rise to a second all-female population, Tremblay's salamander, Ambystoma tremblayi. These females pretend to breed with Jefferson's males in order to initiate cloning. It is also usually classified within Ambystoma laterale. Both these female populations strongly resemble the Blue-spotted salamander.
 
The genera Dicamptodon and Rhyacotriton were formerly included in this family, but are now usually placed into their own families Dicamptodontidae and Rhyacotritonidae. In 2006, a large study of amphibian systematics
Rhyacosiredon used to be considered a separate genus within the family Ambystomatidae. However, cladistic analysis of the mole salamanders found that the existence of Rhyacosiredon makes Ambystoma paraphyletic, since the species are more closely related to some Ambystoma species than those species are to others in Ambystoma. The stream-type morphology of these salamanders (which includes larvae and neotenes with short gills and thicker gular folds) may have led to their misclassification as a different genus.
 
The genus name Ambystoma is traditionally translated as "cup-mouth," but is actually nonsense. Johann Jakob von Tschudi, who described the genus, intended to call it Amblystoma, "blunt-mouth." However, he misspelled the genus as Ambystoma at many points throughout his description. Under biological naming rules, the misspelling Ambystoma takes precedence and cannot be changed. This is especially true because it was widely used by other authors. Occasionally, old specimens and documents will bear the intended genus name
The spotted salamander (Ambystoma maculatum) is a mole salamander common in the eastern United States and Canada. The Spotted Salamander is the State Amphibian of South Carolina. It has recently been found that its embryos have algae living inside them in a mutualistic relation
The spotted salamander is about 6-7.5 inches long. The spotted salamander's main color is black, but can sometimes be a blueish black, dark grey, or even dark brown. There are two rows of yellowish orange spots that run from the top of the head (near the eyes) to the tip of the tail. These rows are uneven. Interestingly, the spotted salamander's spots near the top of the head are more orange and the rest of the spots are more yellow. The underside of the spotted salamander is slate gray.
 
The spotted salamander usually makes its home around hardwood forest areas. They must have a pond as that is the only place they can lay eggs. A spotted salamander spends most of its time beneath ground level. It hides in moist areas under moss-covered logs or stones. These salamanders are secretive and will only exit their underground home on warm rainy nights in Spring, to breed and hunt. However, during the winter, they hibernate underneath ground level. Their defenses from predators include hiding in leaf litter or logs, autonomy, and poison. In ponds or wetlands they hide near the muddy bottoms or hides underneath leaves at the bottom. They have the ability to drop their tails, to distract predators. If a predator of the spotted salamander manages to dismember a part of a leg, tail, or even parts of the brain/head, then it can grow back a new one, although this takes a massive amount of energy. The spotted salamander, like other salamanders show great regenerative abilities, even being able to regenerate limbs and parts of organs. They have large poison glands around the back and neck, which release a toxic white liquid.
 
During the majority of the year, Spotted Salamanders live in the shelter of leaves or burrows in deciduous forests. However, when the temperature rises and there is a higher moisture level, the salamanders make their abrupt migration towards their annual breeding pond. In just one night, hundreds to thousands of salamanders may make the trip to their ponds for mating. Mates usually breed in ponds when it's raining in the spring. Females usually lay about 100 eggs that cling to the underwater plants. The eggs are round, clear, jelly-like clumps that are usually 2 1/2 - 4 inches long. Adults only stay in the water for a few days, then the eggs hatch in 1 to 2 months. Eggs of A. maculatum can have a symbiotic relationship with a green alga, Oophila amblystomatis. Jelly coating prevents the spotted salamander eggs from drying out, however it inhibits oxygen diffusion (required for embryo development). The Oophila alga photosynthesizes and produces oxygen in the jelly. The developing salamander thus metabolizes the oxygen, producing carbon dioxide (which then the alga consumes). When the eggs hatch depends on the water temperatures. As larvae they are usually light brown or greenish-yellow. They have small dark spots and are born with external gills. In 2–4 months the larvae lose their gills, and become juvenile salamanders that leave the water. Spotted salamanders have been known to live up to 20 years and normally return to the same vernal pool every year.