Ancient people observed tailed amphibians crawling from burning logs and dubbed them salamanders (“fire lizards”) believing they were borne in the flames. Of course, the unfortunate salamanders were not borne of the fire but merely hiding in the logs that were brought in from the forest to make the fire.
The Diversity and Distribution of Salamanders
The salamanders have the most generalized body form and locomotion of the living amphibians. Members of order Urodella (Gr. oura, tail + delos, evident) number over 500 species arranged into 10 families and are found on all continents except for Australia and Antarctica.
Roughly one-third of all the known urodelans are found in North America; the highest concentration of these is found in the Appalachian Mountains.This region holds the greatest diversity of urodelans on the planet.
Salamander habitat is generally restricted mostly the northern hemisphere, with the exception of a few species living in the northernmost part of South America. Although common on the European mainland, salamanders are not native to the British Isles.
Within their geographical range, salamanders and newts tend to inhabit cool, moist microhabitats in or near brooks and ponds or under logs and rocks and even in caves. Some species are aquatic throughout life (family Salamandridae or newts), some take to water intermittently, and others are entirely terrestrial as adults.
The Body Plan of Salamanders
In most salamanders the forelimbs and hind limbs are of approximately the same size and set at right angles to the body. However, the limbs are rudimentary or absent altogether in some aquatic and burrowing forms. All types possess a long and distinct post-anal tail (from the anus on back) throughout their life.
Salamanders are typically less than 15 cm (6 inches) long, but the North American hellbender (Cryptobranchus alleganiensis) can reach lengths of 76 cm (2.5 feet) or more. In Japan and China the giant salamander (Andrias japonicusis) reaches 2 m (6-7 feet) and weights up to 30 kg (66 pounds).
Salamanders are carnivorous in all stages of their lives. Their prey consists of arthropods (mainly insects), worms, and small molluscs. Salamanders, like all amphibians, are ectothermic in nature with a low metabolic rate.
Several types of salamanders, including most notably the axolotl (Siredon mexicanum) and the mud puppy (Necturus maculosus), become sexually mature while still retaining some juvenile traits such as external gills.
This condition, known as neoteny, is permanent in the mudpuppy but not in the axolotl. Often the waters the axolotl call home are deficient in iodine and thus the animal cannot produce the thyroid stimulating hormone necessary to force metamorphosis to an adult. This can be experimentally demonstrated by the fact that injecting an axolotl with a small amount of iodine or thyroxin hormone results in metamorphosis quickly progressing to the adult form.
Also, if an axolotl finds its aquatic habitat slowly drying and disappearing to the point where the animal can no longer submerge its body, it may rapidly metamorphose to the adult form.
While the tailed amphibians we call salamanders are not born of fire, they are most certainly creatures of the woods and ponds of the world.
Additional Articles
- The Characteristics of Caecilians investigates the diversity, distribution, and body plan of the legless amphibians – the caecilians.
- The Characteristics of Frogs and Toads investigates the diversity, distribution, and body plan of the most familiar and recognizable of the amphibians – frogs and toads.
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