ASIATIC GIANT SALAMANDERS AND HELLBENDERS: Cryptobranchidae

PHYSICAL CHARACTERISTICS

Asiatic giant salamanders and hellbenders are the largest salamanders, and the largest amphibians. Amphibians (am-FIB-ee-uhns) are vertebrates (VER-teh-brehts), or animals with a backbone, that have moist, smooth skin; are cold-blooded, meaning their body temperature is the same as the temperature of their surroundings; and, in most instances, have a two-stage life cycle. Asiatic giant salamanders and hellbenders are born in the water and spend their entire lives there, never moving to land the way many other amphibians do. There are only three species in this group: Chinese giant salamanders, Japanese giant salamanders, and hellbenders. Asiatic giant salamanders grow to a length of almost 6 feet (1.8 meters) and weigh as much as 50 pounds (23 kilograms). The longest hellbender is about half that length. Asiatic giant salamanders and hellbenders have a broad, flat head and body that makes it easy for them to get under rocks. The tail is flat, too, but from side to side rather than from top to bottom, making it look like an eel's tail.

Asiatic giant salamanders and hellbenders have loose flaps of skin along the sides of their bodies and on the legs. This skin is filled with blood vessels only one cell thick that allow oxygen to pass directly from the water into the salamander's blood. This is how these salamanders breathe. They have lungs and go to the surface sometimes to gulp air but use the lungs mainly for staying stable in the water. The skin of these salamanders also makes lots of slime.

Asiatic giant salamanders and hellbenders have many colors and patterns. They can be gray, brown, greenish brown, yellowish brown, orange-red, or, rarely, white. Some of them have dark blotches or speckles. Japanese giant salamanders and Chinese salamanders have bumps on their heads and throats. The bumps on Japanese giant salamanders are large and separate from one another, but those on Chinese giant salamanders are small and paired.

The legs of Asiatic giant salamanders and hellbenders are thick and strong but short. The eyes are small and do not have eyelids. Hellbenders usually keep one pair of gill openings on each side of their head throughout life, but Asiatic giant salamanders lose these openings during metamorphosis, which can take as long as three years. Gills are organs for obtaining oxygen from water. Metamorphosis (MEH-tuh-MORE-feh-sis) is the process by which some animals change body form before becoming adults. The jaws of Asiatic giant salamanders and hellbenders are very flexible. Bundles of elastic tissue called cartilage (CAR-tih-lej) allow each side of the lower jaw bone to move by itself, so these salamanders can open their mouths very wide to suck in large prey.

GEOGRAPHIC RANGE

Asiatic giant salamanders and hellbenders live in the eastern part of China, the southern part of Japan, and the eastern part of the United States.

HABITAT

Asiatic giant salamanders and hellbenders live in cool streams and rivers with gravel- or rock-covered bottoms. Chinese giant salamanders live in mountain streams, usually at heights less than 5,000 feet (1,500 meters) above sea level. Japanese giant salamanders live at heights less than 2,300 feet (700 meters) above sea level. Hellbenders live below 2,500 feet (750 meters) above sea level.

DIET

Asiatic giant salamanders and hellbenders mainly eat crustaceans and fish. They also eat worms, mollusks, insect larvae, crustaceans, lampreys, fish and fish eggs, frogs and toads and their tadpoles, water-dwelling reptiles, and small mammals as well as the meat of dead animals, their own shed skin and eggs, and one another. Mollusks (MAH-lusks), such as slugs and snails, are animals with a soft, unsegmented body that may or may not have a shell. Larvae (LAR-vee) are animals in an early stage that change form before becoming adults. Crustaceans (krus-TAY-shuns), such as crayfish, are water-dwelling animals that have jointed legs and a hard shell but no backbone.

BEHAVIOR AND REPRODUCTION

Asiatic giant salamanders and hellbenders spend their entire lives in water, rarely coming to the surface. They hunt at night. These salamanders capture prey by quickly opening their flexible jaws and sucking in the prey with a rush of water.

Asiatic giant salamanders and hellbenders breed from August through January, as the days get shorter and the water becomes colder. As the breeding season approaches, these salamanders, especially the males, become more active during the day as they look for places to mate and build nests. They usually choose a place under a rock or log that is protected on the upstream side but has an entrance facing downstream. Tunnels and cracks in the stream or river bank also are good places for hellbender nests.

After finding a good breeding place, a male Asiatic giant salamander or hellbender places himself at the entrance to the nest and lures in or forces in one or more egg-filled females. The male fights a female if she tries to leave before laying her eggs. As the female lays two strings of eggs, the male places himself alongside her. He rocks the lower part of his body and releases sperm over the egg masses. Fertilization (FUR-teh-lih-ZAY-shun), or the joining of egg and sperm to start development, takes place outside the body. The male then guards the eggs and the nest from predators, which include other salamanders in the same species. The larvae are usually 1 to 1.3 inches (2.5 to 3.3 centimeters) long when they hatch. In the wild, Asiatic giant salamanders live more than sixty years, and hellbenders live more than thirty years.

WHAT'S IN A NAME?

People believed the side-to-side movements of hellbenders and the wavy motion of their skin made these animals look like they were experiencing the tortures of hell.

ASIATIC GIANT SALAMANDERS, HELLBENDERS, AND PEOPLE

People have eaten Asiatic giant salamanders and hellbenders for centuries. In parts of Asia these animals were used as medicines and in religious ceremonies and were considered delicacies until they gained protected status. In North America hellbenders have been used for food and fish bait. Asiatic giant salamanders and hellbenders usually are harmless but if attacked can give a severe bite to a finger or hand.

CONSERVATION STATUS

The World Conservation Union (IUCN) lists one species of Asiatic giant salamanders and hellbenders as Critically Endangered and two species as Low Risk/Near Threatened. Critically Endangered means facing extremely high risk of extinction in the wild. Low Risk/Near Threatened means at risk of becoming threatened with extinction in the future.

Much of the habitat of Asiatic giant salamanders and hellbenders has been destroyed or damaged by pollution and by people trying to control the flow of rivers by removing rocks and building dams. Rock removal takes away the salamanders' hiding and breeding places. Dam building forms lakes, which do not have enough fast water flow and are too warm for these salamanders. Habitat also is destroyed by the buildup of silt, which is dirt that is almost like sand. When river or stream banks do not have enough plant life on them to keep the soil in place, as happens when livestock eat all the grass away, when all the trees are cut down, or when farmers do not use good planting practices, the soil is washed from the land into streams and rivers. The silt smothers the eggs of salamanders and other animals and also smothers the invertebrates (in-VER-teh-bre-hts), or animals without backbones, that they eat.

Save the Hellbenders

If you accidentally catch a hellbender while you are fishing, set it free. Do not take it home to keep as a pet.

People may be collecting too many Asiatic giant salamanders and hellbenders. Scientists are successfully breeding Japanese giant salamanders in zoos, and they are trying to figure out how to breed hellbenders, so that these animals can be returned to the wild.

HELLBENDER (Cryptobranchus alleganiensis): SPECIES ACCOUNT

Physical characteristics: Most hellbenders are 11 to 20 inches (28 to 51 centimeters) long and weigh 4 to 5 pounds (1.8 to 2.3 kilograms). The record length is 29 inches (74 centimeters). Male hellbenders are smaller than females. Hellbenders have a broad, flat body and head, like those of a catfish. The tail, however, is flat from side to side, looking like an eel's tail, and has a ridge along the top and the bottom to help in steering. Hellbenders are brown or gray, but during the breeding season some of them change from greenish brown or yellowish brown during the day to orange at night. The toes have rough pads that help the salamanders keep their traction on slippery rocks. Other names for hellbenders are devil dogs, water dogs, mud devils, mountain alligators, and walking catfish.

Hellbenders have floppy folds of skin along the sides of their bodies and on their legs. This skin is filled with many tiny blood vessels that absorb oxygen from the water flowing over the salamander. Hellbenders get about 95 percent of their oxygen this way. They have lungs and can gulp air through them if necessary, but they rarely come to the surface. The lungs are used mainly as internal balloons to help keep the hellbender light enough to walk along the bottom. Hellbenders are very slimy. The slime is made in glands in the skin and tastes bad to predators.

Geographic range: Hellbenders live only in North America. Their range is southern New York south to northeastern Mississippi and west to eastern Missouri and Arkansas. The hellbenders that live in this region are called eastern hellbenders. Other hellbenders live only in south central Missouri and a few rivers in north central Arkansas. These are called Ozark hellbenders.

Habitat: Hellbenders live in clear, fast-moving, rocky streams and rivers less than 2,500 feet (750 meters) above sea level. The riffling movement over rocks keeps the water full of oxygen, and the rocks give the hellbenders places to hide and breed.

Diet: Crayfish are the main prey of hellbenders, but these salamanders also eat insects, snails, fish eggs, and worms. Hellbenders eat by sucking in their prey with a rush of water.

Behavior and reproduction: Hellbenders spend their entire lives in the water. They never make the change to land the way many salamanders do. When they are not breeding, hellbenders live alone. They hide during the day, sometimes with their head sticking out from under a rock. Even though they have an eel-like tail, hellbenders almost never swim. They walk slowly along the river or stream bottom on their short legs. When they are too hot or when there is not enough oxygen in the water, hellbenders rock their bodies from side to side to get more water on their loose flaps of skin.

Hellbenders breed in the late summer to early fall. At breeding time, male hellbenders dig nests under rocks or logs and lure in one or more females. The males sometimes fight one another for the best rocks. Each female lays two strands of 150 to 750 round eggs, which end up in clusters in the nest. Because more than one female may breed with the same male, some nests have almost two thousand eggs, which expand to the size of Ping-Pong balls. The larger a female, the larger are her eggs. The male releases a cloud of sperm over the eggs. Fertilization and development take place outside the body. After they lay their eggs, the male forces the females out of the nest. The males then guard their nests from predators until after the larvae hatch.

Larvae hatch in two to three months, when they are about 1 inch (2.5 centimeters) long. When they start eating small invertebrates, the larvae turn dark brown or black. Newly hatched hellbender larvae have gills that stick up behind their heads. These gills disappear when the larvae are 1.5 to two years old and are 4 to 5 inches (10 to 13 centimeters) long. Over the next five to six years the young hellbenders grow about 0.8 inches (2 centimeters) per year while their heads and bodies flatten. Hellbenders can reproduce when they are about seven years old. Hellbenders live more than thirty years.

Hellbenders and people: Hellbenders are harmless to people. Because they can live only in very clean water, the presence of hellbenders is a sign of good water quality. Some people believe hellbenders interfere with fishing, but they are wrong. Some people try to trap hellbenders to sell as pets, but removing these salamanders from the wild is illegal. In Pennsylvania scientists have found evidence of huge piles of hellbender skeletons that date back ten million years. The scientists believe these fossils are evidence that early people used hellbenders for food and in tribal ceremonies.

Conservation status: The World Conservation Union (IUCN) lists hellbenders as Low Risk/Near Threatened, which means they are at risk of becoming threatened with extinction in the future. The main danger to hellbenders is damage to their habitat through silt buildup, which smothers eggs and the animals the hellbender need for food; loss of trees, which allows silt to wash into the water and removes the shade hellbenders need to keep cool; and pollution of river water by chemicals used on crops and from old mines. Hellbenders absorb the chemicals in polluted water through their skin the same way they absorb oxygen. Some scientists believe too many hellbenders are being collected. They are researching the best conditions for breeding hellbenders so that someday these salamanders can be returned to the wild. ∎

FOR MORE INFORMATION

Books:

Bernhard, Emery. Salamanders. New York: Holiday House, 1995.

Duellman, William E., and Linda Trueb. Biology of Amphibians. Baltimore: Johns Hopkins University Press, 1994.

Gunzi, Christiane. Amphibians and Reptiles of North America. San Diego, CA: Thunder Bay, 1995.

Lawlor, Elizabeth P. Discover Nature in Water and Wetlands. Mechanicsburg, PA: Stackpole, 2000.

Llamas Ruiz, Andres. Reptiles and Amphibians: Birth and Growth. New York: Sterling, 1996.

Petranka, J. W. Salamanders of the United States and Canada. Washington, DC: Smithsonian Institution Press, 1998.

Web sites:

Anft, Michael. "Amphibian Assault." Citypaperonline.http://www.citypaper.com/special/story.asp?id=6657 (accessed on April 19, 2005).

Flanagan, William P., III. "Taxon Management Account: Hellbender Salamander Cryptobranchus alleganiensis alleganiensis (Daudin)." Caudata.org.http://www.caudata.org/cig/taxon_management_account.html (accessed on April 18, 2005).

"Hellbender, Cryptobranchus alleganiensis." Northern Prairie Wildlife Research Center.http://www.npwrc.usgs.gov/narcam/idguide/crypto.htm (accessed on April 19, 2005).

Herman, J. "Cryptobranchus alleganiensis." Animal Diversity Web.http://animaldiversity.ummz.umich.edu/site/accounts/information/Cryptobranchus_alleganiensis.html (accessed on April 19, 2005).

Heying, H. "Cryptobranchidae." Animal Diversity Web.http://animaldiversity.ummz.umich.edu/site/accounts/information/Cryptobranchidae.html (accessed on April 19, 2005).

Johnson, Tom R., and Jeff Briggler. "The Hellbender." Missouri Department of Conservation.http://www.conservation.state.mo.us/documents/nathis/herpetol/amphibian/hellbend.pdf (accessed on April 16, 2005).

"What's a Hellbender?" The Hellbender Homepage.http://hellbenders.sanwalddesigns.com/whats.html (accessed on April 18, 2005).