Caudata

Caudata [kau̇·dad·ə]

(vertebrate zoology)

An equivalent name for Urodela.

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Caudata 

(tailed amphibians), an order of amphibians. The somewhat cylindrical, sometimes greatly elongated, trunk is continuous with the relatively long tail, which is more or less rounded or laterally compressed.

Caudates swim in water by making lateral motions with the tail, pressing their legs to the body and extending them backward. The legs are short and in some representatives, such as Amphiuma, very weak. In the Sirenidae the hind legs are absent. The hind legs have two to five digits. The frontal and parietal bones are paired and not fused. The vertebrae are amphicoelous or opisthocoelous, and the trunk vertebrae have short ribs. The pectoral girdle is cartilaginous. The tibia and fibula are not fused.

Development occurs without metamorphosis. Some adult caudates, such as the Sirenidae and Proteidae, retain a number of features characteristic of the larvae, such as exterior gills, gill slits, and lateral-line organs. In larvae, usually the forelegs appear first. The body length is up to 160 cm (giant salamander).

The order includes 54 genera, united in eight families: Cryptobranchidae, Sirenidae, Proteidae, Salamandridae, Amphiumidae, Ambystomatidae, Plethodontidae, and Hynobiidae. There are about 130 species, which are distributed mainly in the temperate zone of the northern hemisphere; only a few species are found in South America.

Most caudates are wholly aquatic; some live in cave waters, such as the Proteidae and the colorless and eyeless Typhlomolge rathbuni. Some live in water only during the reproductive period. A number of species are wholly terrestrial; a few caudates of the genus Aneides live in trees.

In some terrestrial caudates and in caudates living in rapidly flowing waters the lungs are usually more or less reduced or completely absent, and respiration occurs mainly through the mucosa of the mouth and pharynx, as well as through the skin. A small number of caudates, such as the Amphiumidae and Proteidae, breathe through gills even in the adult stage.

Sexual maturity occurs in the second to third year of life. Some caudates are characterized by neoteny. Some develop breeding colors and engage in a definite courtship during the reproductive period. In the majority, fertilization is internal, by means of a sperm-containing gelatinous capsule (spermatophore), which is taken up by the female into the spermatheca of the cloaca. Caudates deposit three to several hundred eggs. Terrestrial species deposit their eggs in a depression in the soil, beneath leaves, in rotten stumps, in tree hollows, and in other such places. Some species are viviparous or ovoviviparous.

Caudates feed mainly on various invertebrates; they also eat the eggs of fish and other amphibians. Large individuals even swallow small vertebrates. A few species, such as Mertensiella, can shed their tails (autotomy).

There are ten species of Caudata in the USSR, which belong to six genera: Hynobius, Ranodon, Onychodactylis fischeris, Triturus, Mertensiellae caucasicae, and Salamandra.

REFERENCES

Zhizn’ zhivotnykh, vol. 4. Moscow, 1969.
Noble, G. K. The Biology of the Amphibia. New York, 1954.
Bishop, S. C. Handbook of Salamanders: The Salamanders of the United States, of Canada and of Lower California. Ithaca-New York, 1943. (Handbooks of American Natural History, vol. 3. Edited by A. H. Wright.)
Thorn, R. Les Salamandres d’Europe, d’Asie, et d’Afrique du Nord. Paris, 1968.

I. S. DAREVSKII