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Newt
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A newt is a salamander that lives in the water as an adult. Newts occur in the Pleurodelinae subfamily (family Salamandridae), found in North America, Europe and Asia. Newts metamorphose through three distinct developmental life stages, including aquatic larval, terrestrial juvenile, and aquatic adult. The larvae leave the water as a terrestrial juvenile form called an eft. The adult form has a lizard-like body and is either aquatic or semi-aquatic.
etymology for this term has gone through a complex twist of old Middle English variations.
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A newt is a salamander that lives in the water as an adult. Newts occur in the Pleurodelinae subfamily (family Salamandridae), found in North America, Europe and Asia. Newts metamorphose through three distinct developmental life stages, including aquatic larval, terrestrial juvenile, and aquatic adult. The larvae leave the water as a terrestrial juvenile form called an eft. The adult form has a lizard-like body and is either aquatic or semi-aquatic.
Etymology
The etymology for this term has gone through a complex twist of old Middle English variations. The oldest form of the name is eft, which is still used for newly metamorphosed specimens, but according to the Oxford English Dictionary it changed for unknown reasons first to euft and then to ewt. For some time it remained as an ewt, but the "n" from the indefinite article an shifted to form a newt. The sexually aquatic mature stage was also called an ewte, with similar etymology roots linking an ewte, newt, "euft", and eft: "small lizard-like animal," .
Characteristics
Like all members of the order Caudata, newts are characterised by a lizard-like body with four equal sized limbs and a distinct tail. Aquatic larvae have true teeth on both upper and lower jaws and external gills. They have the ability to regenerate limbs, eyes, spinal cords, hearts, intestines, and upper and lower jaws. The cells at the site of the injury have the ability to de-differentiate, reproduce rapidly, and differentiate again to create a new limb or organ. One theory is that the de-differentiated cells are related to tumour cells since chemicals which produce tumours in other animals will produce additional limbs in newts.
Development
The main breeding season for newts is between the months of February and June. After courtship rituals of varying complexity, which take place in ponds or slow moving streams, the eggs are fertilised outside the female's body. Their eggs are laid singly, attached to aquatic plants. This distinguishes them from the free-floating eggs of frogs or toads, that are laid in clumps or in strings. Plant leaves are usually folded over and adhered to the eggs to protect them. The tadpoles, which resemble fish fry but are distinguished by their feathery external gills, hatch in about three weeks. After hatching they eat algae, small invertebrates or other tadpoles.
During the next few months the tadpoles undergo metamorphosis, during which they develop legs, and the gills change into air-breathing lungs.Some species, such as the North American newts, also become more brightly coloured during this phase. Once fully metamorphosised they leave the water and live a terrestrial life, when they are known as "efts". Only when the eft reaches adulthood will the North American species return to live in water, rarely venturing back onto the land. Conversely, most European species live their adult lives on land and only visit water to breed.
Toxicity
Many newts produce toxins in their skin secretions as a defense mechanism against predators. Taricha newts of western North America are particularly toxic; the Rough-skinned newt (Taricha granulosa) of the Pacific Northwest produces more than enough tetrodotoxin to kill an adult human.
Most newts can be safely handled, provided that the toxins they produce are not ingested or allowed to come in contact with mucous membranes or breaks in the skin. After handling, proper hand-washing techniques should be followed due to the risk from the toxins they produce and bacteria they carry, such as salmonella.
. It is, however, illegal to handle or disturb Great Crested Newts in the UK without a licence. A 29-year-old man in Coos Bay, Oregon, who had been drinking heavily, swallowed a rough-skin newt Taricha granulosa for a dare. He died later that day despite hospital treatment.
Systematics
About two thirds of all species of the family Salamandridae are commonly called "newts", compromising the following genera:
- Calotriton, Spanish brook newts
- Cynops, firebelly newts
- Echinotriton, crocodile newts
- Lissotriton, small bodied newts
- Mesotriton, Alpine newts
- Neurergus, spotted newts
- Notophthalmus, Eastern newts
- Ommatotriton, banded newts
- Pachytriton, paddle-tail newts
- Paramesotriton, warty newts
- Pleurodeles, ribbed newts
- Taricha, Pacific newts
- Triturus, crested newts
- Tylototriton, crocodile newts
The term "newt" has traditionally been seen as a functional term for salamanders living in water, and whether they constitute a natural systematic unit is uncertain. However, newer molecular analysis tend to support they actually do. All newts are members of the subfamily Pleurodelinae (of the family Salamandridae). However, some of the genera sometimes listed as Pleurodelinae are not "newts" (Salamandrina and Euproctus). Whether these are are basal to the subfamily or derived, making the newts an evolutionary grade, (animals with different ancestry that have evolved with similar characteristics) is not known.
Distribution
The three common European genera are the crested newts (Triturus sp.), the smooth newts and palmate newts (Lissotriton sp.) and the banded newts (Ommatotriton sp.). Other species present in Europe are the Iberian ribbed newt (Plurodeles waltl), which is the largest of the European newts, the pyrenean brook newt (Calotriton sp.); the European brook newt (Euproctus sp.) and the Alpine newt (Mesotriton alpestris).
In North America, there are the Eastern newts (Notophthalmus sp.), of which the red-spotted newt (Notophthalmus viridescens) is the most abundant species, but it is limited to the area east of the Rocky Mountains. The three species of coastal or Western newts are the red-bellied newt, the California newt, and the rough-skinned newt, all of which belong to the genus Taricha, which is confined to the area west of the Rockies.
In Southeast Asia and Japan, species commonly encountered in the pet trade include the fire belly newts (Cynops sp.), the paddletail newts (Pachytriton sp.), the crocodile newts (Tylototriton sp.), and the warty newts (Paramesotriton sp.). In the Middle East there are the middle eastern newts (Neurergus sp.).
Conservation status
Newt populations have fallen across the world, due to pollution or destruction of their breeding sites and terrestrial habitats, and countries such as the USA and the UK have taken steps to halt their decline. In the UK they are protected under the Wildlife and Countryside Act 1981 and the Habitat Regulations Act 1994. It is illegal to catch, possess or handle Great Crested Newts without a licence and it is also illegal to cause them harm or death, or to disturb their habitat in any way. The IUCN Red List categorises the species as ‘lower risk’
Although the other UK species, the smooth newt and palmate newt are not listed, the sale of either species is prohibited under the Wildlife and Countryside Act, 1981.
In Europe, nine newts are listed as "strictly protrected fauna species" under appendix II of the Convention on the Conservation of European Wildlife and Natural Habitats:
- Euproctus asper
- Euproctus montanus
- Euproctus platycephalus
- Triturus carnifex
- Triturus cristatus
- Triturus dobrogicus
- Triturus italicus
- Triturus karelinii
- Triturus montandoni
The remaining European species are listed as "protected fauna species" under appendix III.
Cultural references
External links
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- Species account from the Iowa Reptile and Amphibian Field Guide
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