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Andrias japonicus

By Laura Winkler

Geographic Range

Andrias japonicus is native to the northern region of Kyushu Island and western Honshu island of Japan. ("Smithsonian National Zoological Park", 2003)

Habitat

Andrias japonicus is found at elevations between 180 and 1,350 meters. These salamanders reside in and around the cold, swift, mountain streams of the Japanese islands. These waters provide enough oxygen to diffuse through the epidermis of A. japonicus, facilitating an aquatic lifestyle. As with other cryptobranchid salamanders, A. japonicus tends not to leave the water and is thus particularly sensitive to receding mountain streams. ("Arkive--Images of Life", 2004; Gadow, 1901; Semlitsch, 2003)

  • Aquatic Biomes
  • rivers and streams
  • Range elevation
    180 to 1,350 m
    590.55 to ft

Physical Description

Giant Japanese salamanders (Andrias japonicus) grow to approximately 1.5 meters in length and can weigh up to 25 kg. The long body of A. japonicus is covered with a wrinkled grey, black, and green epidermis that provides camoflauge. The tail is long and wide, and there are two pairs of legs, which are close in size. Andrias japonicus is endowed with minimal vision. Small, lidless eyes sit on the top of the wide, flat head. Gas exchange occurs through the epidermis. The wrinkles of the warty epidermis provide increased surface area, facilitating the exchange of carbon dioxide and oxygen with the water. Capillaries run close to the surfaces of the skin, allowing for the easy diffusion of gases.

The slow metabolism of Japanese salamanders allows these amphibians to live without consuming food for weeks at a time. Giant Japanese salamanders differ from other closely related species in that these particular salamanders lack gill openings and also have unique modifications with their branchial structures. ("Arkive--Images of Life", 2004; Gadow, 1901; Parker, 2001; Pough, et al., 2001)

  • Range mass
    25 (high) kg
    55.07 (high) lb
  • Range length
    1.5 (high) m
    4.92 (high) ft

Development

Andrias japonicus grows continously throughout life. As with other amphibians, A. japonicus undergoes three developmental stages, including egg, larva, and adult forms. Hatching occurs 12 to 15 weeks after fertilization. Eggs usually measure 6 mm by 4 mm, and are mostly yellow in color.

Metamorphosis in this species is incomplete. Adults do not develop eyelids, and retain a single pair of closed gill slits on the neck. Andrias japonicus retains its larval teeth for life, and has lungs which are vestigial, performing no gas exchange. ("Arkive--Images of Life", 2004; Gadow, 1901; Parker, 2001; Pough, et al., 2001; Sleeper, 1997; Zug, et al., 2001)

Reproduction

Andrias japonicus begins the reproductive process in early autumn. In late August, the salamanders congregate at nesting sites, or spawning pits, which simply consist of rocky caverns, burrows, or hollowed impressions within the sandy streambed. Males aggressively compete to occupy these spawning pits. Once males have secured the nesting sites, females enter the nesting site to begin the fertilization process. Females approach males and proceed to make a spin-like motion. The female then releases her eggs within the spawning pit while the male fertilizes them. More than one female may release eggs into the same spawning pit. Males guard the eggs in the spawning pits until they hatch, 12 to 15 weeks after fertilization. This protects the eggs from other male salamanders and possible predators such as fish. Males ferociously defend and occupy a particular spawning pit for many years. Smaller males have been killed and eaten by larger males during the reproductive season. ("Arkive--Images of Life", 2004; Pough, et al., 2001; Sleeper, 1997)

Females release 400 to 500 eggs in the spawning pit protected by a male. These eggs are held together with a string-like substance and resemble threaded beads on a string. Fertilization is external. Eggs hatch 12 to 15 weeks after fertilization. The age at sexual maturity for A. japonicus is not known, although given male competition, it is likely that at least for males, successful breeding requires a large size. ("Arkive--Images of Life", 2004; Sleeper, 1997)

  • Breeding interval
    Breeding occurs once yearly.
  • Breeding season
    Breeding begins in early August.
  • Range number of offspring
    400 to 500
  • Range time to hatching
    12 to 15 weeks

The exact amount of parental investment found in A. japonicus has not been thoroughly investigated. Females provision eggs with large quantities of nutrients, ensuring their survival. Males may contribute to the survival of the young through their protection of spawning pits. A male protects his spawning pit from predatory fish and other male A. japonicus. Males tend to protect these spawning pits until the eggs have hatched, 12 to 15 weeks after fertilization. ("Arkive--Images of Life", 2004; Pough, et al., 2001)

  • Parental Investment
  • pre-fertilization
    • provisioning
    • protecting
      • male
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male

Lifespan/Longevity

Giant Japanese salamanders can live for over fifty years. However, it is unlikely that most individuals live this long. Large numbers of offspring are produced each season, so mortality early in life is probably high. (Sleeper, 1997)

Behavior

Andrias japonicus is nocturnal, usually sleeping underneath stream rocks during daylight hours. These salamanders are natatorial and motile. For normal movement, Giant Japanese salamanders walk on the bottoms of streams whereas an undulating type of movement is used to quickly travel short distances. Andrias japonicus uses a side-to-side movement to keep water circulating near the epidermis, so that deoxygenated water moves away from the skin, and oxygen-rich water replaces it. ("Arkive--Images of Life", 2004; Gadow, 1901; Zug, et al., 2001)

Andrias japonicus is territorial, with large males often killing smaller rivals in defense of spawning pits. Apparently as a means of defnese, A. japonicus expells a secretion that smells like the Japan pepper plant. This expulsion quickly hardens to a gelatinous substance in the open air. Although its function underwater is not understood, it may protect the individual expelling it. (Gadow, 1901; Pough, et al., 2001)

Home Range

The home range for A. japonicus has not been reported.

Communication and Perception

With small eyes that provide little visual acuity, these nocturnal amphibians use the senses of smell and touch to perceive their environments. Little is known about the communication methods of A. japonicus. Tactile communication is apparently important between rival males, as well as between a male and female during breeding. The "smelly" expulsion produced under threat suggests that chemical communication may have some role in this species. The role of auditory cues in communication is unknown. ("Arkive--Images of Life", 2004)

Food Habits

Andrias japonicus is a carnivorous dietary generalist which engulfs prey by quickly opening and closing its warty mouth while sucking. By creating negative pressure within the mouth, A. japonicus produces asymmetrical suction. Assuming that A. japonicus follows the same suction habits as other cryptobranchid salamanders that suck asymmetrically, Giant Japanese salamanders drop one side of their jaw 10 to 40 degrees in order to suck in their prey. Because these salamanders feed in water, saliva is not needed.

These salamanders are known to consume:

Fish (Class Osteichthyes).

Insects (Class Insecta).

Crustaceans (Subphylum Crustarea).

Giant Japanese salamanders also eat worms, although details on the types of worms consumed are not available. ("Natural History Museum", 2005; Pough, et al., 2001; Sleeper, 1997)

  • Animal Foods
  • fish
  • insects
  • terrestrial non-insect arthropods

Predation

Fish (Class Osteichthyes) are a main predator of A. japonicus eggs.

Humans have also used these salamanders as a source of food. They may still be used some traditional medicinal practices.

The long bodies of A. japonicus are covered with a wrinkled grey, black, and green epidermis in the adult stage that allows them to blend into the surrounding area and avoid potential predators. ("Arkive--Images of Life", 2004; "Smithsonian National Zoological Park", 2003)

  • Anti-predator Adaptations
  • cryptic
  • Known Predators

Ecosystem Roles

Andrias japonicus serves as host for parasites. Studies have shown that giant Japanese salamanders can house parasitic roundworms, specifically Spiroxys hanzaki. (Hasegawa, et al., 1998)

Commensal/Parasitic Species
  • Parasitic roundworms (Spiroxys hanzaki)

Economic Importance for Humans: Positive

Andrias japonicus is occasionally hunted and is sold for profit in Asia as a delicacy. There are reports that this species may be used in some traditional medicines. ("Arkive--Images of Life", 2004)

Economic Importance for Humans: Negative

Local fishermen of the Japanese islands claim that A. japonicus consumes small sweetfish that inhabit the same mountain streams. Many locals fear that their fishing economy is damaged by the salamanders predation of small fish. (Parker, 2001)

Conservation Status

The IUCN Red List of Threatened Species lists A. japonicus as a near threatened or lower risk species.

Other Comments

The first living specimen of A. japonicus that was captured and brought to a Western nation was found by von Siebold in 1829. Von Siebold is credited with the discovery of this species. This particular A. japonicus lived at least 52 years in captivity. (Gadow, 1901)

Contributors

Laura Winkler (author), Kalamazoo College, Ann Fraser (editor, instructor), Kalamazoo College.

Nancy Shefferly (editor), Animal Diversity Web.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

drug

a substance used for the diagnosis, cure, mitigation, treatment, or prevention of disease

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

freshwater

mainly lives in water that is not salty.

heterothermic

having a body temperature that fluctuates with that of the immediate environment; having no mechanism or a poorly developed mechanism for regulating internal body temperature.

indeterminate growth

Animals with indeterminate growth continue to grow throughout their lives.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

metamorphosis

A large change in the shape or structure of an animal that happens as the animal grows. In insects, "incomplete metamorphosis" is when young animals are similar to adults and change gradually into the adult form, and "complete metamorphosis" is when there is a profound change between larval and adult forms. Butterflies have complete metamorphosis, grasshoppers have incomplete metamorphosis.

motile

having the capacity to move from one place to another.

mountains

This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

visual

uses sight to communicate

References

2004. "Arkive--Images of Life" (On-line). Japanese giant salamander. Accessed October 07, 2005 at http://www.arkive.org/species/GES/amphibians/Andrias_japonicus.

2005. "Natural History Museum" (On-line). Highlights--giant salamander. Accessed October 07, 2005 at http://internt.nhm.ac.uk/jdsml/museum/tring/highlights/detail.dsml?beginIndex=1&listPageURL=index.dsml%3F.

2003. "Smithsonian National Zoological Park" (On-line). Giant salamanders. Accessed October 07, 2005 at http://nationalzoo.si.edu/Publications/ZooGoer/2003/2/GiantSalamander.cfm.

Gadow, H. 1901. Amphibia and Reptiles. New York: The MacMillan Company.

Hasegawa, H., A. Miyata, T. Doi. 1998. Spiroxys hanzaki n. sp. (Nematoda: Gnathostomatidae) collected from the giant salamander, Andrias japonicus (Caudata: Cryptobranchidae), in Japan. The Journal of Parasitology, 69: 33-42.

Parker, G. 2001. Giant salamanders lurk in Japan. The Newsletter of the Colorado Herpetological Society, 28.

Pough, H., R. Andrews, J. Cadle, M. Crump, K. Wells. 2001. Herpetology. New Jersey: Prentice Hall.

Semlitsch, R. 2003. Amphibian conservation. Washington: Smithsonian Books.

Sleeper, B. 1997. Giant (really big) salamanders. Pacific Discovery, 50: 36-37.

Zug, G., L. Vitt, J. Caldwell. 2001. Herpetology. San Diego: Academic Press.

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