The amber salamander, amber-colored salamander, tortoiseshell salamander, or Stejneger's oriental salamander (Hynobius stejnegeri) is a species of salamander in the family Hynobiidae, endemic to Japan. Its natural habitats are temperate forests and rivers. It is threatened by habitat loss.
As its name suggests, the external appearance is that of semitransparent blackish brown ground color, blotched with bright amber. Its ventral surface is lighter and without blotches. The amber salamander has a snout-to-vent length of 76–85 mm and a total length of 137–155 mm. However, individuals have been reported to have been nearly 200 mm in length. The head appears to be oval when viewed from above and the eyes are prominent, and a gular fold is present. It has a robust and cylindrical body with 13 to 14 costal grooves. It is similar to Hynobius kimurae in color, but has only four toes, a longer series of vomerine teeth, and a longer body.
According to a recent study led by Matsui, Nishikawa and Tominaga, Hynobius stejnegeri and Hynobius yatsui are identical. The name H. yatsui is therefore relegated to a subjective junior synonym of H. stejnegeri. According to the same study, a population of Hynobius stejnegeri from Kyushu should be treated as a new species Hynobius ikioi.
Habitat and ecologyEdit
This species of salamander is found only in Kyushu, Japan, and is distributed among the mountainous areas of the prefectures of Kumamoto, Miyazaki, and Northern Kagoshima. The various regional populations of the amber salamanders are separated by a number of geographic barriers, including the Gokase River and the Aso Volcano, the Kirishima Volcano, and the Yatsushiro Sea. It can be found in both terrestrial (land) and freshwater ecosystems. Its land habitat is located in temperate forests which consist of mountainous areas of broad-leaved, evergreen forests, as well as mixed forests. The freshwater habitat is located in wetlands of permanent rivers, streams, and creeks, including waterfalls. Habitats have been discovered in and around mountainous streams at altitudes ranging from 500–1500 m. They return to upstream areas to breed, and this is also where the larvae develop. Their diets are made up of insects, spiders, worms, aquatic insect larvae, and crustaceans, and they have been known to resort to cannibalism. The unique possible cryptic coloration is hypothesized to act as a camouflage among fallen leaves. If the color pattern is an effective deterrent from predators, then this characteristic is likely due to strong selection. A genetic variance of 4% was found to be due to phenological circumstances in the populations of amber salamander between two regions separated by geographic isolation.
The egg sacs produced by the males are quite long, ranging from 17 to 30 cm and differ from other species of the same genus, Hynobius boulengeri, by not having the prominent whip-like formation on the free end. Each clutch ranges from 21–57 eggs, and the female remains close to her clutch until the eggs have hatched. The hatched larvae are a yellowish color and the fingers and toes sport black claws. These larvae undergo a metamorphosis while living in the stream, and emerge in September and October of the same year they are laid, but many wintering larvae remain in the stream until spring or summer of the following year when they emerge.
The amber salamander is harmed by hunting and trapping, logging, and wood harvesting. Major threats also include the construction of roads, deforestation, erosion, and pollution. The amber salamander is also used for medicine and food. H. stejnegeri is also used in the medical field of comparative hepatology. In an experiment, when the mother was removed, the eggs vanished, presumably eaten by freshwater crabs or some other predator. This suggests survival of the larvae is contingent on the mother's protection.
The extent of occurrence is less than 20,000 km2, the species are fragmented in distribution, regionally only in Japan, with a continuing decline in the extent and quality of their habitat. The amber salamander was considered near threatened by the Environment Agency of Japan in 2000. It was determined near threatened by the International Union for Conservation of Nature (IUCN) in 2021. Now, the amber salamander is on the Earth's Endangered Creatures List. It is designated a natural monument by Kumamoto Prefecture. There is a need to ensure the capture of this species from the wild is managed in a sustainable way.
- IUCN SSC Amphibian Specialist Group 2021. Hynobius yatsui. The IUCN Red List of Threatened Species 2021: e.T177960108A177504137. https://doi.org/10.2305/IUCN.UK.2021-1.RLTS.T177960108A177504137.en. Downloaded on 24 April 2021.
- Dunn, E.R. (1923). "The salamanders of the family Hynobiidae". Proceedings of the American Academy of Arts and Sciences. 58 (13): 445–523. doi:10.2307/20026019. JSTOR 20026019.
- Frost, Darrel R. (2015). "Hynobius stejnegeri Dunn, 1923". Amphibian Species of the World: an Online Reference. Version 6.0. American Museum of Natural History. Retrieved 29 August 2015.
- Facts about Amber-coloured Salamander (Hynobius stejnegeri). Encyclopedia of Life. Retrieved Oct 25, 2012
- Winters, N. (2006–1207). AmphibiaWeb – Hynobius stejnegeri. Retrieved Oct 25, 2012
- Goris, R.C. and Maeda, N. (2004). Guide to the Amphibians and Reptiles of Japan. Krieger Publishing Company, Malabar, Florida ISBN 1-57524-085-8.
- Thorn, R., (1969). Les salamandres d’Europe, d’Asie et d’Afrique du Nord. Editions Paul Lechevalier, Paris.
- Sparreboom, M. (2011-03-14). Science. naturalis – stejnegeri. Retrieved Oct 25, 2012
- Matsui, M.; Nishikawa, K.; Tominaga, A. (2017). "Taxonomic relationships of Hynobius stejnegeri and H. yatsui, with description of the amber-colored salamander from Kyushu, Japan (Amphibia: Caudata)". Zoological Science. 34 (6): 538–545. doi:10.2108/zs170038. PMID 29219040.
- Nishikawa, K.; Matsui, M. & Tanabe, S. (2005). "Biochemical phylogenetics and historical biogeography of Hynobius boulengeri and H. stejnegeri (Amphibia: Caudata) from the Kyushu Region, Japan". Herpetologica. 61: 54. doi:10.1655/03-89.
- Akiyoshi, H. & Inoue, A. M. (2012). "Comparative histological study of hepatic architecture in the three orders amphibian livers". Comparative Hematology. 11: 2. doi:10.1186/1476-5926-11-2. PMC 3517316. PMID 22905994.
- Glenn, C. R. (2006). Earth's Endangered Creatures – Worldwide Endangered Species List – Animals. Retrieved Oct 25, 2012