Giant salamander

Giant salamanders
Temporal range:
Paleocene - Present,[1] 60–0 Ma
Andrias japonicus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Amphibia
Order: Urodela
Suborder: Cryptobranchoidea
Family: Cryptobranchidae
Fitzinger, 1826
Genera

The Cryptobranchidae are a family of fully aquatic salamanders commonly known as the giant salamanders. A single species, the hellbender (Cryptobranchus alleganiensis) occurs in the eastern United States, while Asian species occur in both China and Japan. They are the largest living amphibians known today. The Japanese giant salamander (Andrias japonicus), reaches up to 1.44 m (4.7 ft), feeds on fish and crustaceans, and has been known to live for more than 50 years in captivity.[2] The Chinese giant salamander (Andrias davidianus) can reach a length of 1.8 m (5.9 ft).[3]

Taxonomy

The family name is from the Ancient Greek krypto ("hidden"), and branch ("gill"), which refer to how the members absorb oxygen through capillaries of their side-frills, which function as gills.

Clade Pancryptobrancha (Cryptobranchidae + Ukrainurus)

Fossil history

Andrias scheuchzeri

In 1726, the Swiss physician Johann Jakob Scheuchzer described a fossil as Homo diluvii testis (Latin: Evidence of a diluvian human), believing it to be the remains of a human being who drowned in the biblical flood. The Teylers Museum in Haarlem, Netherlands, bought the fossil in 1802, where it is still exhibited. In 1812, the fossil was examined by Georges Cuvier, who recognized that it was not human. After being identified as a salamander, it was renamed Salamandra scheuchzeri by Holl in 1831. The genus Andrias was coined six years later by Tschudi. In doing so, both the genus, Andrias (which means "image of man"), and the specific name, scheuchzeri, ended up honouring Scheuchzer and his beliefs. It and the extant A. davidianus cannot be mutually diagnosed, and the latter, only described in 1871, is therefore sometimes considered a synonym of the former.[4]

Description

Cryptobranchids are large salamanders, with large folds of skin along their flanks. These help increase the animals' surface area, allowing them to absorb more oxygen from the water. They have four toes on the fore limbs, and five on the hind limbs. Their metamorphosis from the larval stage is incomplete, so the adults retain gill slits (although they also have lungs), and lack eyelids. They can reach a length of 1.8 m (5.9 ft), though most are considerably smaller today.[3]

Distribution and habitat

In Japan, their natural habitats are threatened by dam-building. Ramps and staircases have been added to some dams to allow them to move upstream to areas where they spawn. [5]

Behaviour

The Japanese giant salamander has lived for as long as 52 years in captivity.[2]

Feeding

The Chinese giant salamander eats aquatic insects, fish, frogs, crabs, and shrimp.[6] They hunt mainly at night. As they have poor eyesight, they use sensory nodes on their heads and bodies to detect minute changes in water pressure, enabling them to find their prey.[7]

Reproduction

During mating season, the salamanders travel upstream, where the female lays two strings of over 200 eggs each. The male fertilizes the eggs externally by releasing his sperm onto them, and then guards them for at least three months, until they hatch.[6] At this point, the larvae live off their noticeable stored fat until ready to hunt. Once ready, they hunt as a group rather than individually.

Scientists at Hiroshima City Asa Zoological Park in Japan have recently discovered the male salamander will spawn with more than one female in his den. On occasion, the male "den master" will also allow a second male into the den; the reason for this is unclear.

Cultural references

References

  1. ↑ Bredehoeft, Keila E.; Schubert, Blaine W. (2015). "A Re-Evaluation of the Pleistocene Hellbender,Cryptobranchus guildayi". Journal of Herpetology. 49: 157. doi:10.1670/12-222.
  2. 1 2 Andrias japonicus. AmphibiaWeb: Information on amphibian biology and conservation. 2012. Berkeley, California: AmphibiaWeb. Retrieved 13 December 2012.
  3. 1 2 Andrias davidianus. AmphibiaWeb: Information on amphibian biology and conservation. 2012. Berkeley, California: AmphibiaWeb. Retrieved 13 December 2012.
  4. ↑ Frost, Darrel R. (2011). "Andrias Tschudi". Amphibian Species of the World: an Online Reference. Version 5.5 (31 January 2011). Electronic database accessible at http://research.amnh.org/vz/herpetology/amphibia/. American Museum of Natural History, New York, USA. Retrieved 13 December 2012.
  5. 1 2 "Giant Salamanders Helped to Spawn" 31 December 2009. National Geographic Society. Retrieved 13 December 2012.
  6. 1 2 Lanza, B., Vanni, S., & Nistri, A. (1998). Cogger, H.G. & Zweifel, R.G., ed. Encyclopedia of Reptiles and Amphibians. San Diego: Academic Press. p. 69. ISBN 0-12-178560-2.
  7. ↑ Glenn, C. R. (2006). "Earth's Endangered Creatures - Chinese Giant Salamander Facts" Retrieved 13 December 2012.
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