Amphibians
Defining Characteristics:
Vertebrates
Live part of their lives in water and part on land
Young have gills for breathing underwater
Ectothermic - depend on warmth from sunlight to become warm and active
Metamorphosis - as they develop, young change in body shape, diet, and lifestyle
Class: Amphibia
Number of Species: Over 5,500
Amphibians live part of their lives in water and part on land. They are vertebrates and are also ectothermic; they cannot regulate their own body heat, so they depend on sunlight to become warm and active. Amphibians also can't cool down on their own, so if they get too hot, they have to find a burrow or some other shade. In cold weather, amphibians tend to be sluggish and do not move around much.
Metamorphosis
Young amphibians do not look like their parents. Generally called larvae, they change in body shape, diet, and lifestyle as they develop, a process called metamorphosis. A frog is a good example, starting out as a tadpole with gills to breathe underwater and a tail to swim with. As the young frog gets older, it develops lungs, legs, and a different mouth. Its eyes also change position, and it loses its tail. At this point it is an adult frog and spends most of its time hopping on land rather than swimming like a fish in the water.
Moist is best
Most amphibians have soft, moist skin that is protected by a slippery secretion of mucus. They also tend to live in moist places or near water to keep their bodies from drying out. Many adult amphibians also have poison-producing glands in their skin, which make them taste bad to predators and might even poison a predator that bites or swallows them. Some of these amphibians, like poison frogs, are brightly colored as a warning: Don't eat me, or you'll be sorry!
Three groups
There are about 5,500 known amphibian species, divided into three main groups: salamanders and newts, caecilians, and frogs and toads. The largest amphibian is the Chinese giant salamander at nearly 6 feet (1.8 meters) and 140 pounds (63 kilograms), and the smallest is the gold frog at 0.39 inches (1 centimeter) long.
Leaping to the rescue
To help save amphibians, San Diego Zoo Wildlife Alliance is active in several areas of amphibian conservation. There are a remarkable number of amphibians in our care, which you can see when you visit San Diego Zoo. We have joined with other organizations to help save endangered frogs and support amphibian conservation programs.
