Amphibians (frogs and salamanders are the main types) are a super-cool, freaky group of animals. Although amphibians need to live in or near water to survive, individual species have evolved incredible adaptations that allow them to survive in wild places all over the world.
The word “amphibian” is from the Greek word amphibios, which means “double life.” In a sense, amphibians are two kinds of animal in one. When they’re young, they live in water and have gills like fish. When they become adults, they are more like reptiles, living on land and breathing air.
You may already know the typical lifecycle of an amphibian. The mother deposits a mass of jelly-like eggs in a freshwater pond or stream. Then the eggs hatch into larvae (tadpoles in the case of frogs), which swim around like fish. After a few weeks, the larvae begin to go through metamorphosis, growing arms and legs and radically changing form. Finally, the adults hop or crawl onto land.
But not all amphibians follow the rules. In fact, some species have very unusual lifecycles.
Amphibians have been around for a very long time. Early fossils show that the first amphibians evolved from fish over 300 million years ago. That’s way before the first dinosaurs stomped into existence.
Since amphibians first showed their slimy skins millions of years ago, they have evolved into a fascinatingly varied group, including over 7,000 species worldwide. Amazingly, scientists still find new amphibian species all the time. In 2012, nearly 200 new ones were discovered.
One of the most incredible and special things about amphibians is their skin. Although many adult amphibians have lungs, almost all adult amphibians “breathe” primarily through their skin. Their skin is so moist and their blood vessels are so close to the surface that they can draw oxygen directly into their bloodstreams. However, their skin has to remain wet to make it possible for them to get oxygen this way, which is why amphibians like to live in wetland habitats. Land-dwelling amphibians also have the ability to ooze mucus from special glands to keep their skin moist. Sometimes, as in the case of poison-dart frogs, the mucus contains toxins to ward off predators.
Every species of amphibian is unique, colorful, and fascinating. Unfortunately, these creatures are in serious trouble all over the world. Many amphibians have already gone extinct and hundreds of species, maybe thousands, are endangered. One of the biggest threats to amphibians is the chytrid fungus, which causes an infectious disease called chytridiomycosis. The infection attacks the amphibians’ skin, which is very vulnerable, and can quickly lead to death. As many as 200 species have already been wiped out.
One of the most threatened species, the Panamanian golden frog, is the national animal of Panama. It’s like the bald eagle is to the United States. One unique thing about this frog is that it doesn’t have eardrums. To communicate, it waves an arm in the air to let other frogs know it’s there. Unfortunately, about 10 years ago, the chytrid fungus ripped through the frogs’ river valley habitat, and they are now gone from the wild. Scientists and conservationists (people who want to save animals and their habitats) rescued some healthy golden frogs from the wild before the disease could get to them. Now, the frogs are being raised in captivity, and scientists hope one day to return the frogs to their Panama river homes.
Sometimes the chytrid fungus is the final blow to a species that’s already threatened by habitat destruction, climate change, or pollution. But amphibian lovers are trying to fight back. Here’s what’s happening with the Kihansi spray toad. This yellowish little toad lives beside a powerful waterfall in Tanzania, Africa. There, the spray from the waterfall had created a wonderful, wet micro-habitat. These toads are unusual in that they don’t lay eggs and there is no tadpole phase. The tiny baby toads are born fully formed and ride around on their mothers’ backs. In the past, the call of the Kihansi toad could be heard all around the falls. But about ten years ago, the construction of a new dam drastically reduced the spray from the falls and changed the toad’s habitat. That, combined with the chytrid fungus and the introduction of pesticides into the river above the falls, caused the Kihansi spray toad to vanish from the wild. Rescued toads were raised in zoos—and in 2012, 2,000 were released back into the wild in Tanzania. Now there’s an artificial sprinkler system that recreates the spray from the falls. Everyone involved in the reintroduction project is crossing their fingers that the captive-raised toads will re-populate their old home.
Amphibians are an important part of ecosystems around the world. They eat insects and other small invertebrates that can sometimes be pests, and they help keep our environment in balance. As scientists study amphibians, they are discovering that many have features that could be helpful to people. The special skin of amphibians produce all kinds of unusual chemicals, and some of those chemicals can fight diseases that hurt humans. For example, the phantasmal poison frog makes a chemical that can be used as a powerful painkiller. And the fire-bellied toad produces a substance that can reduce high blood pressure.Written by Margaret Mittelbach [wp-simple-survey-20]