Chordate Zoology - textbook - Y. V. Tsaryk - 2013

Chapter 5. SUPERCLASS TETRAPODS (LAND VERTEBRATES) TETRAPODA, seu QUADRIPEDA.

ANAMNIOTES (ANAMNIA) AND AMNIOTES (AMNIOTA)

5.1. CLASS AMPHIBIANS, OR AMPHIBIA AMPHIBIA

5.1.3. Systematics and characteristics of representatives of modern orders of the class Amphibia

5.1.3.2. Order Caudata Urodela, seu Caudata

This order comprises about 619 extant species. In members of this order, the HEAD merges imperceptibly into an elongated trunk, and the tail is always laterally compressed; the forelimbs and hindlimbs are of almost equal length, although in some species they are poorly developed, and in sirens, the hind pair is reduced. They crawl or swim by bending their body and tail in a serpentine manner. Many caudates have transitioned to an aquatic lifestyle. They possess well-developed Skin glands. They are distributed mainly in the Northern Hemisphere and are absent from Australia. In Africa, only four species occur (compared to about 800 species of other amphibian orders), and a few species inhabit northern South America. They are common in mountainous regions where anurans are scarce. The order comprises nine families.

The most primitive are the giant salamander family Cryptobranchidae and the Asiatic salamander family Hynobiidae. Members of these families have amphicoelous vertebrae and exhibit external Fertilization. The Japanese giant salamander Andrias japonicus reaches a body length of up to 1.6 m and lives in the mountain streams of Eastern China and Japan, while the hellbender Cryptobranchus alleganiensis reaches 70 cm and inhabits mountain rivers in southeastern North America. The Asiatic salamander family includes the Siberian salamander Salamandrella keyserlingii, which reaches a length of 8-9 cm; it inhabits the permafrost zone and is highly resistant to low temperatures (down to -6°C), remaining active at 0°C; it lives on the forested shores of Water bodies from Komi and the Northern Urals to Kamchatka, Sakhalin, and Northeast China.

The mole salamander family Ambystomatidae comprises 37 species distributed in North and Central America. The best-known is the tiger salamander Ambystoma tigrinum. Adults inhabit the shores of water bodies and hide during the day. They reach a length of 15-23 cm. The aquatic larvae of many mole salamanders—axolotls—can reach the size of adults without undergoing metamorphosis, reproducing sexually (neoteny) (Fig. 5.7, Zh).

The siren family Sirenidae. Representatives of this family inhabit North America. These are neotenic larvae, possibly of mole salamanders, in which the adult stage was lost during evolution. They have very small and weak forelimbs, and retain external gills and gill slits throughout their lives. They breathe using both gills and well-developed Lungs; they live in swamps and feed on invertebrates and small amphibians (Fig. 5.15, D).

The mudpuppy and olm family Proteidae includes six species of neotenic larvae, possibly derived from some extinct salamanders. One of them, the olm Proteus anguinus (Fig. 5.15, V), lives in the underground waters of the Balkan Peninsula. It has an eel-like, reddish body 25–30 cm long, with small limbs bearing three toes on the forelimbs and two on the hindlimbs. Three pairs of feathery external gills are located on the sides of the head. The tail is short and laterally compressed. The eyes are tiny or hidden under the skin. Fertilization is internal; the female lays up to 80 eggs, but all except two in the lower part of the oviducts degenerate (undergo lysis). The products of lysis are consumed by the two developing larvae. At a length of about 1 cm, the larvae emerge and lead an independent life.

The common mudpuppy Necturus maculosus mainly inhabits cold lakes in eastern North America. It is active year-round, can freeze into ice at low temperatures, and revives upon thawing.

The amphiuma family Amphiumidae is represented by three species, one of which is the two-toed amphiuma Amphiuma means (Fig. 5.15, G). It has an eel-like body (89-100 cm long). The forelimbs are poorly developed, ending in 2-3 toes. The eyes are covered with skin. In adults, the external gills are reduced, but one pair of gill slits is retained; lungs are developed. The vertebrae are amphicoelous. Similar to true salamanders, it retains larval characteristics throughout its life. It inhabits lakes and swamps in southeastern North America.

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Fig. 5.15. Species of caudate amphibians:

A - smooth newt Lissotriton vulgaris; B - fire salamander Salamandra salamandra; V - olm Proteus anguinus;

G - amphiuma Amphiuma means; D - lesser siren Siren intermedia; E - spotted salamander Ambystoma maculatum; Zh - axolotl Ambystoma tigrinum

The true salamander family Salamandridae includes 89 species. Members of this family have well-developed eyelids; the vertebrae are opisthocoelous; adults have functional lungs, while external gills are reduced and gill slits are closed. They are distributed in Europe, Asia, North Africa, and North America. Salamanders have a clumsy body and a large tail without a keel. The body length is 10-28 cm. The fire salamander Salamandra salamandra (see Fig. 5.15, B) and the alpine salamander Salamandra atra inhabit the banks of mountain streams and humid mountain forests; many species are ovoviviparous, and fertilization is internal. The coloration of the fire salamander is black with bright yellow spots. In Ukraine, the fire salamander inhabits beech and mountain spruce forests of the Lviv, Ivano-Frankivsk, and Zakarpattia regions, as well as the mountainous part of the Chernivtsi region. It stays in shelters during the day and hunts at night. It moves slowly and clumsily. Fertilization takes place both in water and on land. The female "gives birth" to 20-40 larvae. The Caucasian salamander Mertensiella caucasica reproduces by laying fertilized eggs in water.

There are seven species of salamandrids in Ukraine. The body shape is lizard-like; larvae breathe through external gills. The most common is the smooth newt Lissotriton vulgaris (see Fig. 5.15, A), found in the Carpathians, forest-steppe, and forest zones, as well as in river valleys of the steppe zone; it reaches 8 cm, sometimes even 11-12 cm. The Carpathian newt Lissotriton montandoni is distributed in the Carpathians, often found at altitudes of 1,000 m above sea level, reaches 8 cm, and is endemic. The great crested newt Triturus cristatus has a body length of 15-18 cm. The alpine newt Ichthyosaura alpestris inhabits mountain water bodies and moves to damp places in summer. It occurs in the northwestern part of the Carpathians, ascending to altitudes of 500-1500 m above sea level. The tail of newts is slightly longer than or equal to the length of the trunk. In summer, newts live in stagnant or slow-flowing water. They swim quite fast using their tail and can remain submerged for 2-3 minutes. They shed their skin periodically, sloughing it off like a glove and immediately eating it. They reproduce only in water. Metamorphosis lasts three months. They feed on a variety of animal food, mainly insects and other invertebrates.

The lungless salamander family Plethodontidae is the most numerous in the order, with about 418 species (Fig. 5.7, Zh). They are characterized by the reduction of lungs and the loss of the Pulmonary Circulation. Some species live in mountain streams, while others inhabit caves and humid forests. They have a protrusible Tongue with an expansion at the tip for catching insects. They inhabit North America, with some penetrating into South America, and only two species of cave salamanders are found in the mountainous regions of Southern Europe.