Amphibians are vertebrate animals within which we find, among others, the order Caudata (Urodela), in which more than 700 species are located and which are generally known as salamanders, although, as we will see, other common names are also used depending on the group. Its main and most diverse distribution is in the Holarctic region of North America, although it is also present in South America, North Africa, Europe and Asia.
Continue reading this article on our site and learn about the types of salamanders and their characteristics.
Characteristics of salamanders
Salamanders are a complex group that exhibit traits peculiar to amphibians, such as the following:
- Presence of tail in all its stages.
- Lacking certain skull bones and not having a middle ear, even though they are not deaf.
- Neoteny (maintenance of juvenile traits in adulthood) is a characteristic in various species.
- The elongated, cylindrical body forms a right angle with the extremities, which with a few exceptions are usually the same size.
On the other hand, although most have internal fertilization, in some types of salamanders it is external. Likewise, they present a variety of sizes, weights and colors, some are poisonous and also depending on the group they differ in the type of habitat.
Depending on the author, salamanders are classified into nine or 10 families, as some separate the family Dicamptodontidae [1], while others include it as a genus in the Ambystomatidae. Here we will use the first classification, which is proposed by the Integrated Taxonomic Information System [2]
Family Ambystomatidae: mole salamanders
Within this group of salamanders are certain species known as axolotls or axolotls This family is distributed exclusively in North America, from Alaska to Mexico. Some have aquatic habits in the larval stage and terrestrial when they are adults, returning to the water only to reproduce. On the other hand, others remain in the water all their lives.
There are 33 species of the genus Ambystoma and 4 of the Dicamptodon. Some do not undergo metamorphosis, while others do, even depending on the conditions, certain species may or may not transform. A very representative example of this type of salamander that does not undergo metamorphosis is found in the Mexican axolotl (Ambystoma mexicanum), while one that does is the flat-headed axolotl (Ambystoma amblycephalum).
Family Amphiumidae: amphiumas
This group of salamander species is also known as 'Congo eels', although it has nothing to do with this region, probably a misinterpretation of conger eels as true eels.
Distributed exclusively in the United States, specifically in the southeast of the country. They have a eel-like appearance, with long bodies that differ from most types of salamanders. They are characterized by being neotenic, without eyelids, with very small limbs and lack of external gills. Reproduction is through internal fertilization and they have been identified as aggressive animals.
There are only three species within a single genus, the Amphiuma:
- Three-toed amphiuma (Amphiuma tridactylum)
- Two-toed amphiuma (Amphiuma means)
- One-toed amphiuma (Amphiuma pholeter)
In the image we see the amphiuma of two fingers.
Family Cryptobranchidae: giant salamanders
Another type of these amphibians are the giant salamanders, named precisely because of their large size. There are only three species:
- Chinese giant salamander (Andrias davidianus)
- Japanese giant salamander (Andrias japonicus)
- Hellbender Salamander (Cryptobranchus alleganiensis)
The first presents the largest sizes, reaching up to 1, 8 meters long and 65 kg in weight The names of the first two indicate its origin, while the third is limited to the eastern United States, developing in well-oxygenated waters with fast courses.
Adult forms do not have gills and lungs are thought to be nonfunctional, so breathers through their skin Nor They have eyelids and their fertilization is external. They are characterized by expelling a very unpleasant smell, they are aggressive and territorial, they even mutilate each other with their teeth.
Family Hynobiidae: Asian salamanders
Asian salamanders are an ancient group that is divided into two subfamilies, Hynobiinae and Onychodactylinae, with a total of 78 species They are distributed from Afghanistan and Iran to Japan. Certain species are able to live in habitats with temperatures below 0 degrees, so they freeze and remain dormant. Likewise, some, such as the clawed salamanders, which belong to the genus Onychodactylus, developed species of claws on their fingers.
The forms of feeding vary within this group, so some species feed by suction in the water or use their tongue to simulate a projectile. Being a type of primitive salamanders, they have external reproduction.
In the image we can see Fischer's clawed salamander (Onychodactylus fischeri).
Family Plethodontidae: lungless salamanders
This type of salamander is the most diverse, as it includes some 477 species distributed mainly in America and, to a lesser extent, in Europe and Asia. Their name comes from the fact that they completely lack lungs, so breathing is carried out exclusively through the skin and the membranes present in the pharynx.
They are found in various types of habitats, such as aquatic, terrestrial, arboreal and some are even excavators and others live in caves. They can present tiny sizes, as is the case of the species of the genus Thorius, which measure barely 30 mm in length. They are a very interesting group, where some species of salamanders with good binocular vision are located, others, to escape predators, place their limbs under the body and roll down slopes.
An example of this type can be found in the salamander of the Sierra de Juárez, which is barely 20 mm long.
Proteidae family: mudpuppies
Names such as water dogs and elm trees are used in these salamanders. The proteids are a fairly diverse group, numbering about eight species in all and are considered to be the advanced salamanders. They are characterized by being neotenic, with bushy external gills and aquatic habits. Its reproduction is by internal fertilization.
The largest distribution is in North America and one species in Europe. They live both in caves and outside of them. Within the examples of the group we can mention the Neuse river water dog (Necturus lewisi) and the olm or proteus (Proteus anguinus). The latter is the one we see in the image and, as a curious fact, we can say that it has no eyes. Discover more Animals without eyes in this other article.
Family Rhyacotritonidae: torrent salamanders
This type is also a not very diverse group, of which a single genus has been identified and four species, allendemic to the northeast coast of the United States Although they undergo metamorphosis, they retain certain juvenile features such as conical teeth and some reduced or cartilaginous bones. They are adapted to live in waters with fast currents. Fertilization is internal and they have very little tolerance for temperature increases, so they live in cold environments. In addition, they are very susceptible to habitat alteration.
Some examples of salamanders belonging to this group are:
- Olympic torrent salamander (Rhyacotriton olympicus)
- Southern torrent salamander (Rhyacotriton variegatus)
In the image we can see the southern torrent salamander.
Family Salamandridae: salamanders and newts
Probably the most popular group is the salamanders of this family, which also includes certain species known as newts. They are particularly distributed in North America, Asia and Europe They are considered to be about 123 species in 21 genera They usually have amphibious habits, although some remain in the water, others only return to reproduce.
Many have bright colors that warn of their toxicity due to the presence of poisonous glands in their skin, such as the North American Taricha newts, considered to be among the amphibians poisonous that existCertain species are neotenic, fertilization is internal and, although most lay their eggs, there are some viviparous cases in the group, such as the Atif salamander (Lyciasalamandra atifi). Generally, these types of salamanders have a complex courtship process. The fire salamander (Salamandra salamandra) is one of the typical examples of the group.
In the image we see Atif's salamander.
Family Sirenidae: mermaids
These are the most peculiar of all types of salamanders, to the point of eventually being considered outside the group. They lack hind legs, the front ones are very tiny and this, together with their elongated bodies, makes them resemble eels. They also have no external gills or eyelids and are very good diggers. The mouth is shaped like a horned beak and they only have patches of teeth that are not connected to the jaw bone. They are neotenous, with external fertilization and can measure up to 95 cm in length.
Two genera are recognized and Five species, which inhabit exclusively the southeastern United States and northern Mexico. We have an example in the minor siren (Siren intermedia).
