Species Tiger Salamander (Ambystoma tigrinum) RED LIST Basic Characteristics of an Amphibian The amphibians were the first vertebrates on land in late Devonian times. Frogs and salamanders and the wormlike animals called caecilians are the major members of the class Amphibia that still exist today. Amphibians are a class of "cold-blooded" vertebrate animals that have glandular skins lacking any skin coverings such as fur, scales or feathers. Metamorphosis - the Two Lives of Amphibians Amphibian means "two lives," a reference to the metamorphosis of some frogs and their relatives. The tadpole, the larval stage of a frog, is usually an aquatic plant-eater with gills and a long, finned tail. The tadpole lacks legs and swims by moving in a wave-like fashion like its fishlike ancestors. During the transformation (metamorphosis) that leads to the "second life," legs develop and the gills disappear. The young tetrapod crawls onto shore and begins its life as a terrestrial hunter. In spite of the name amphibian, however, most members of the class do not go through the aquatic larval stage (tadpole), but develop directly into the adult form. Reproduction The amphibian egg has no shell, and it dries up quickly in dry air. Oviparous amphibians (those that lay eggs in which the embryos have as yet developed little if at all) generally lay their eggs in ponds or swamps or at least in moist environments. There are also live-bearing amphibians, and even some viviparous species, that retain the eggs in the female reproductive tract, where embryos can develop without drying out. Breathing Through the Skin Even as adults, most frogs and other amphibians must maintain close ties with water. Although they have lungs, most amphibians carry out much of their gas exchange with the environment across their moist skin. The skin of most amphibians is permeable to water, and the animals dessicate quickly in a dry environment. Therefore amphibians are most abundant in damp habitats such as swamps and rain forests. Even toads and frogs adapted to drier habitats spend much of their time in burrows where the humidity is high. Endangered Species Living amphibians are classified in three orders: the Anura (frogs and toads), the Caudata (salamanders and newts) and the Apoda (Caecilians). An example of a rare amphibian of the Caudata order that lives in the dry interior region of southern British Columbia is the Tiger Salamander (Ambystoma tigrinum). There are about 350 species of newts and salamanders known throughout the world, eight of which are known to occur in British Columbia. this section sponsored by: Industry Canada

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