Japanese Giant Salamander
Tagged: animal, animals, fish, insectAndrias japonicus
Restricted to just two mountainous areas, the Japanese giant salamander’s mountain stream habitat is under threat from damming and deforestation. Collection has also depleted numbers. Fortunately, the salamander is now fully protected by international trade restrictions. The Japanese giant salamander and its close relative the Chinese giant salamander from China and Taiwan are the largest salamanders in the world. An inhabitant of mountain streams with clear, cool water, the Japanese giant salamander is similar in anatomy and habits to the hell bender of North America, and the two Asian species are sometimes known as Oriental hell benders. The Japanese giant salamander has a heavily built, slightly compressed body and a flat head, with small eyes and nostrils at the tip of its snout. Its skin is rough and warty, with many wrinkles and folds, giving the impression that its body is too small for its skin. Two prominent folds run along the whole length of its body. The tail, which makes up about a quarter of its total length, is flattened from side to side and has a fin along the upper side. The limbs are small and also slightly flattened. In color the salamander is reddish or grayish brown with a darker mottled pattern, and it is paler on the underside. Males and females are similar in size and appearance, except that the male develops a swollen cloaca (cavity into which the alimentary canal, genital, and urinary ducts open) during the breeding season. The Japanese giant salamander is a retiring animal by day, hiding under rocks or in a burrow. It emerges at night in search of food, which includes fish, worms, and crustaceans such as crayfish. It has an unusual arrangement of jawbones and muscles, which enables it to suck its prey into its mouth. It requires the clean, well-oxygenated water that is found only in fastÂflowing streams and so is confined to altitudes between 980 and 3,300 feet (300 and 1,000 m). The Chinese giant salamander is found in a similar habitat, but also occurs in mountain lakes.
Breathing through the Skin
The giant salamanders show a form of pedomorphosis, retaining many aspects of the larval form into adult life. Unlike some pedomorphic salamanders, however, giant salamanders lose their external gills when they are about 18 months old and about 4.5 inches (12 cm) in length. Thereafter they rely on their skin to absorb oxygen from the water. The skin of giant salamanders contains a higher density of blood capillaries than most salamanders, and the many wrinkles and folds in the skin increase the surface area over which oxygen is absorbed. When resting, the salamanders sway slowly from side to side; this serves to gently stir up the water, ensuring that well-oxygenated water is always close to their skin.
Paternal Care
plays a more active role than is true for most salamanders. He digs a pit in the gravel on a stream bed, defending his territory aggressively against rival males. At the same time, he displays to attract a female into the pit. The female lays 400 to 600 eggs in strings that are between 7 and 60 feet (2 and 18 m) in length, and the male sheds sperm onto them. Mating attracts the attention of other, usually smaller males, who enter the nest and also shed sperm on the eggs. After mating, the female leaves the male, who guards the eggs until they hatch, after about two months. The newly hatched larvae disperse from the nest and reach maturity at about three years of age. Breeding begins in the fall (August to September). The male Japanese giant salamanderGiant salamanders are very long-lived; one animal, in Amsterdam Zoo, lived to be 52 years old.
Protected Species
The large size of the Japanese giant salamander, together with its specific habitat requirements, means that it was never an abundant creature. As a result, it has been particularly badly affected by deforestation and the damming of rivers, activities that destroy the clear, well- oxygenated streams it prefers. Japanese giant salamanders have also been collected in the past and sent to many museums, aquaria, and zoos throughout the world. However, this kind of trade is now tightly controlled, the species having been given full protection under the CITES treaty.
Statistics:
- Family: Cryptobranchidae
- World population: Unknown
- Distribution: Southern Japan; islands of Honshu and Kyushu
- Habitat: Rocky mountain streams with clear, fast-flowing, and well oxygenated water
- Size: Length: 8-56 in (20-140 cm)
- Form: Large salamander; long, flattened body; rough, warty skin with many wrinkles and folds. Laterally compressed tail with dorsal (back) fin. Broad, flat head; small eyes. Reddish or grayish brown on upper body; paler below
- Diet: Fish, worms, and crustaceans
- Breeding: Fall (August-September)
- Related endangered species: Chinese giant salamander
Salamander
Any member of a group of about 400 species of amphibians that have tails and that constitute the order Caudata. The order comprises 10 families, among which are newts and salamanders proper (family Salamandridae) as well as hellbenders, mud puppies, and lungless salamanders. They most commonly occur in freshwater and damp woodlands, principally in temperate regions of the Northern Hemisphere. Salamanders are generally short bodied, four legged, moist-skinned animals, about 10 to 15 cm (4 to 6 inches) long. They are often boldly patterned or brightly coloured. The largest of the order is the Chinese giant salamander, Andrias davidianus, which grows to 1.5 m (5 feet) in length. Typical salamanders undergo a larval stage that lasts for a period of a few days to several years. Larval forms have external gills and teeth in both jaws and lack eyelids. These and other larval features may persist into sexual maturity a condition known as neoteny. A mud puppy (Necturus maculosus) of eastern North America and the axolotl (Ambystoma mexicanum) of central Mexico are common species that exhibit this phenomenon. Salamanders feed on insects, worms, snails, and other small animals, including members of their own species. Like other amphibians, they absorb water through their skins, and they require a moist habitat. In regions where the temperature goes below freezing, they often hibernate. Most adult salamanders hide by day and feed by night. Some remain hidden underground until the breeding season, or they may emerge only when levels of moisture and temperature are appropriate. Many species, especially in the family Plethodontidae, are strictly terrestrial and avoid ponds and streams. Fertilization in primitive forms (suborder Cryptobranchoidea) is external. In higher forms, fertilization is usually internal; males of such forms often produce a spermatophore, or sperm case, which the female takes into her body through the cloacal opening. Breeding often occurs in the water, but certain members of the Salamandridae and most species of the Plethodontidae families breed on land.
Family Dicamptodontidae (giant salamanders)
Large salamanders, to 35 cm; stout-bodied and large-headed with large, long limbs; larvae live for several years, and 1 species is permanently larval; Paleocene (66.4–57.8 million years ago) to present; northwestern United States and extreme southwestern Canada; 1 genus, Dicamptodon, and 4 species.
Family Plethodontidae (lungless salamanders)
Very small to moderate size, 3.5 to about 30 cm; includes the most specialized and most terrestrial salamanders and the only truly tropical species; lungless; nasolabial grooves present; no ypsiloid cartilage; Early Miocene (23.7–16.6 million years ago) to present; North America, Central America, and most of South America; 6 species in Europe (Sardinia, southern France, and north-central Italy); 25 genera, placed in 2 subfamilies: Desmognathinae, with 3 genera (including Desmognathus) and about 14 species in eastern North America, and Plethodontinae, with 22 genera (including Plethodon in North America and the bolitoglossines Bolitoglossa in Central and South America, Batrachoseps in western North America, and Hydromantes in western North America and the central Mediterranean region) and about 232 species.
Family Proteidae (olms and mud puppies)
The olm is blind, has little pigment, has an elongated body, and is cave-dwelling; mud puppies live in lakes and streams, have eyes, and are normally pigmented; elongate bodies, length to 45 cm; limbs with 3 (olm) or 4 fingers, 2 (olm) or 4 toes; external gills present; Late Paleocene to present; 2 genera (Proteus, native to the northern Balkan Peninsula, and Necturus, of eastern North America) and 6 species.
Family Rhyacotritonidae (torrent salamanders)
Small dwellers of streams, springs, and seeps; length to 9 cm; 4 fingers and 5 toes; no gills in adults; no fossil record; northwestern United States; 1 genus, Rhyacotriton, and 4 species.
Family Salamandridae (salamanders and newts)
Generalized form and habit; moderate size, to 30 cm; limbs with 4 fingers, 4 to 5 toes; usually no external gills or spiracle; Paleocene to present; Europe; North Africa; Middle East; Afghanistan to Japan, China, and northern Vietnam; eastern and western North America; 14 genera (including Triturus and Salamandra in Europe, Notophthalamus and Taricha in North America, and Cynops in Japan) and about 56 species.
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