Asiatic Salamanders: Hynobiidae

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ASIATIC SALAMANDERS: Hynobiidae

HOKKAIDO SALAMANDER (Hynobius retardatus): SPECIES ACCOUNTS
JAPANESE CLAWED SALAMANDER (Onychodactylus japonicus): SPECIES ACCOUNTS
SEMIRECHENSK SALAMANDER (Ranodon sibiricus): SPECIES ACCOUNTS

PHYSICAL CHARACTERISTICS

Asiatic salamanders are small to medium-sized salamanders. Most of these salamanders are 4 to 10 inches (10 and 25 centimeters) long, although some species grow to a length of 12 inches (30 centimeters). Most of these salamanders are dull sandy brown to dark olive, but a few species have colorful spots on their backs.

There are two main groups of Asiatic salamanders. One group lays a large number of eggs, and the larvae (LAR-vee), or animals in an early stage, spend one year in development before metamorphosis (MEH-tuh-MORE-feh-sis), or a change in body form to become an adult, is finished. The other group lays a much smaller number of eggs, and the larvae take two to three years to go through metamorphosis.

Some Asiatic salamanders that live in mountain streams have a hard structure on their toes. One species has claws. Some species have a horny covering on their feet. These structures and coverings help the salamanders grasp the ground. Some Asiatic salamanders have four instead of five toes. The arrangement of the teeth, which are located on the roof of the mouth, is an important characteristic for identifying the genus (JEE-nus) and species (SPEE-seez) of Asiatic salamanders. Some species of Asiatic salamanders have very small lungs, and others have no lungs at all. The small size or lack of lungs may be part of the salamanders' water-dwelling lifestyle. The larvae of Asiatic salamanders have four pairs of gill slits. Gills are organs for obtaining oxygen from water.

GEOGRAPHIC RANGE

Asiatic salamanders live only in Asia. Their range extends from Japan, Taiwan, and the mainland of China westward to Afghanistan, Iran, and Kazakhstan in central Asia. To the north, Asian salamanders live on the Kamchatka peninsula, the island of Sakhalin, and in Siberia and Mongolia westward beyond the Ural Mountains. Siberian salamanders are the only Asiatic salamanders that enter European Russia and are the only salamanders that live north of the Arctic Circle.

HABITAT

Some Asiatic salamanders, such as clouded salamanders, live only in lowlands. Others live only in the mountains. Many live 6,600 to 13,000 feet (2,000 to 4,000 meters) above sea level. The record for highest home belongs to the Tibetan stream salamander, which lives in western China at a height of 14,000 feet, or about 2.5 miles (4,250 meters).

Some Asiatic salamanders live in water all year. These salamanders live mainly in mountain streams with cool, fast-flowing water. During daylight hours, they stay under rocks in the water. Sometimes they hide under large rocks on shore, but they are never far from water. In some species of Asiatic salamanders the adults spend most of the year on land, but in the breeding season (February to June) they travel to and gather at breeding sites, which are either ponds or mountain streams with running water. Most species breed in only one of the types of water. For example, Korean salamanders breed only in ponds. Some species, however, such as Chinese salamanders, breed in both ponds and streams. They have been found under rocks and grass and in burrows. Some species have been dug out of soil.

EYE OF NEWT, BREAKFAST OF BAT?

Paghman mountain salamanders have the most bizarre diet of all Asiatic salamanders. Baby bats have been found in their stomachs. The salamanders live in caves, which they share with bats. The baby bats fall into the water, where they are caught and eaten by the salamanders.

DIET

Asiatic salamanders, both larvae and adults, eat insects and other invertebrates (in-VER-teh-brehts), which are animals without backbones. Hokkaido salamanders and Longdong stream salamanders eat others of their own species.

BEHAVIOR AND REPRODUCTION

Asiatic salamanders hunt for food at night. Scientists know little else about how these salamanders behave outside of breeding season. The breeding season varies from late winter to early summer. Some Asiatic salamanders breed in late winter and early spring. The eggs develop in ice-cold water mixed with ice and snow. Others breed in early summer. The breeding season may be as late as July for some species in western China.

Males of all but one species of Asiatic salamanders release sperm into the water while the females are laying sacs of eggs. The exception is male Semirechensk salamanders, which place sacs of sperm on rocks or plants. In all species, fertilization (FUR-teh-lih-ZAY-shun), or the joining of egg and sperm to start development, takes place outside the body. The females lay two groups of eggs, one batch of eggs coming from each ovary. The ovaries (OH-vuh-reez) are the organs that make eggs. The eggs are contained in jelly-like sacs, which attach to rocks or plants in ponds, streams, or marshes. Egg sacs that do not attach to something usually are not fertilized (FUR-teh-lyzed). The number of eggs in each sac varies, ranging from three in Japanese clawed salamanders to 105 in Siberian salamanders.

In most species of Asiatic salamanders the female chooses an object such as a rock or plant, grasps it firmly, and lays her egg sacs on it. The sacs stick to the rock or plant. After she releases part of the egg sac, the female lets go of the plant or rock and floats backward. A male waiting nearby immediately moves onto the egg sac. The male often pushes and kicks the female with its legs and presses on the egg sacs with its cloaca to fertilize the eggs. The cloaca (kloh-AY-kuh) is a chamber in both males and females that holds waste from the kidneys and intestines as well as eggs and sperm before they are released to the outside. The male's activity may help to speed up egg laying. Male clouded salamanders guard and vigorously defend the egg sacs they have fertilized.

Most Asiatic salamander eggs hatch in three to five weeks, depending on the temperature. The larvae of some salamander species that are not well developed when they hatch have a balancer on each side of the head. The balancers, which look like whiskers, support the head until the front legs develop, and then they fall off. The larvae of most stream-breeding Asiatic salamanders are well developed when they hatch and do not have balancers.

ASIATIC SALAMANDERS AND PEOPLE

Asiatic salamanders have no known importance to people.

CONSERVATION STATUS

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

The primary threats to the survival of Asiatic salamanders are their small geographic ranges and small numbers. Many Asiatic salamanders live in only a small area on one island or mountain. These areas in Japan and China are getting smaller and are being separated from one another. Damage to habitat caused by people is another problem for these salamanders.

HOKKAIDO SALAMANDER (Hynobius retardatus): SPECIES ACCOUNTS

Physical characteristics: Hokkaido salamanders are 4 to 7 inches (10 to 18 centimeters) long. There are eleven or twelve grooves along the sides of the body, and the tail is long. The legs and toes are long compared with those of other Asiatic salamanders. The back is dark brown with a few blurry spots. Some Hokkaido salamanders keep the larval body form even though they grow to adult size.

Geographic range: Hokkaido salamanders live on Hokkaido, the northernmost of the main islands of Japan.

Habitat: Hokkaido salamanders live less than 6,600 feet (2,000 meters) above sea level. During the breeding season they live in slow-moving streams and ponds. When they are not breeding, these salamanders live on land under grass, rocks, and leaf litter on the forest floor but often visit bodies of water.

Diet: The larvae of Hokkaido salamanders eat small water-dwelling invertebrates. Adults eat insects, crustaceans, water worms, and, sometimes, fish. Crustaceans (krus-TAY-shuns) are water-dwelling animals that have jointed legs and a hard shell but no backbone. Hokkaido salamander larvae packed close together in large groups sometimes eat other Hokkaido salamander larvae but usually do not eat their brothers and sisters.

Behavior and reproduction: Scientists know how Hokkaido salamanders reproduce but little else about how these salamanders behave. Breeding starts when the snow begins to melt and the water temperature is 37 to 41°F (3 to 5°C). In most areas, the breeding season is in April, but at higher elevations, breeding may not start until early June. Both male and female Hokkaido salamanders travel to and gather at their breeding sites. Mating and egg laying take place at night. The females lay two egg sacs, which attach to twigs and grass. Each egg sac usually contains thirty to fifty eggs, but there may be as many as ninety-three eggs in a sac. Larvae finish metamorphosis within one year, but if the water is cold, metamorphosis can take two or even three years.

Hokkaido salamanders and people: Hokkaido salamanders have no known importance to people.

Conservation status: Hokkaido salamanders are not considered threatened or endangered. ∎

JAPANESE CLAWED SALAMANDER (Onychodactylus japonicus): SPECIES ACCOUNTS

Physical characteristics: Japanese clawed salamanders are 4 to 7 inches (10 to 18 centimeters) long. The body is thin, and the tail is long. The back is brown with orange spots. There also are orange spots on the back of the head and on the legs. Orange stripes run along the center of the back. The larvae have clawlike structures on their toes. Adults have these "claws" only during the breeding season. Japanese clawed salamanders do not have lungs.

Geographic range: Japanese clawed salamanders live on two Japanese islands, Honshu and Shikoku.

Habitat: Japanese clawed salamanders live more than 3,300 feet (1,000 meters) above sea level. When they are not breeding, these salamanders live on land but very close to water. Their favorite places are under wet rocks or logs beside a stream. They also live under logs on the forest floor, in tree holes, and in other damp places.

Diet: Japanese clawed salamanders eat insects and their larvae, spiders, millipedes, snails, tadpoles, and fish larvae.

Behavior and reproduction: Scientists know how Japanese clawed salamanders reproduce but little else about how these salamanders behave. The males breed every two years, and the females breed every three years. The breeding season is in May, but in some areas it extends into June. The females lay eggs at night, usually at the source of a mountain stream. Each of the two egg sacs contains three to eight eggs, for a total of seven to fifteen eggs per female. Larvae take three years to finish metamorphosis.

Japanese clawed salamanders and people: Japanese clawed salamanders have no known importance to people.

Conservation status: Japanese clawed salamanders are not considered threatened or endangered. ∎

SEMIRECHENSK SALAMANDER (Ranodon sibiricus): SPECIES ACCOUNTS

Physical characteristics: Semirechensk salamanders are 6 to 10 inches (15 to 25 centimeters) long. The tail is as long as the rest of the body and has a ridge along the top. The body is brown with scattered black spots. Adult Semirechensk salamanders have small lungs.

Geographic range: Semirechensk salamanders live in the Ala Tau mountains and the Tien Shan mountains of eastern Kazakhstan and western China.

Habitat: Semirechensk salamanders live in mountain streams and marshes 5,000 to 9,000 feet (1,500 to 2,750 meters) above sea level.

Diet: Larvae of Semirechensk salamanders and salamanders that have just completed metamorphosis eat the larvae of water-dwelling invertebrates. Adults eat water-dwelling and land-dwelling invertebrates.

Behavior and reproduction: Semirechensk salamanders hunt for food at night. The larvae begin hunting four to eight days after they hatch. These salamanders continue to hunt during metamorphosis. The breeding season is May to July. Semirechensk salamanders take two to three years to go through metamorphosis. Male Semirechensk salamanders are the only Asiatic salamanders that make bags of sperm. They attach the sperm bags to the undersides of rocks and plants, and females attach their egg sacs to the same rocks and plants, where fertilization takes place. Male Semirechensk salamanders, not the females, choose the breeding sites.

Semirechensk salamanders and people: Semirechensk salamanders have no known importance to people.

Conservation status: The World Conservation Union (IUCN) lists Semirechensk salamanders as Endangered, or facing very high risk of extinction in the wild. They are under protection in both Russia and China. The small geographic range and damage to their habitat are the main threats to the survival of Semirechensk salamanders. These salamanders do well in captivity, and some scientists are trying to return them to the wild. ∎