Description
Hynobius nigrescens has a snout to vent length of 60-80 mm and a total length of 120-190 mm. It is a relatively large hynobiid salamander with a long, broad tail that comprises half its total length. Its limbs are also long and when they are adpressed to the flank, the toes of the fore- and hindlimbs overlap by a space of 1-3 costal grooves. It has 11 very deep costal grooves and a deep dorsal groove as well. The dorsal surface is uniformly black, flecked with tiny light dots, and on its ventral side the light color predominates.

Hynobius lichenatus often occurs in sympatry and may even breed in the same ponds, but H. nigrescens can be distinguished by the combination of relatively large size, deep costal and dorsal grooves, and very dark coloration (Goris and Maeda 2004).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Japan

	View distribution map in BerkeleyMapper.
	View Bd and Bsal data (1 records).

H. nigrescens is found in most of the northern part of Honshu and on Sadogashima Island at elevations of sea level to above 2500 m. (Goris and Maeda 2004). It occurs from coastal areas to alpine zones in forests and montane grasslands (IUCN 2006).

Life History, Abundance, Activity, and Special Behaviors

Hynobius nigrescens belongs to the family Hynobiidae, which is one of only two salamander families exhibiting external fertilization of eggs. This species is one of several where the males take part in a "scramble competition" for females (Hasumi 1994)[3756]. Depending on the locality and altitude, Hynobius nigrescens breeds from February to July, at the onset of the first spring thaw, in not-too-shallow ponds or in the backwater pools of slowly moving brooks. Males arrive first and hang by their hind legs from submerged branches or twigs. When a female arrives, she selects and rests on a suitable branch and makes her presence known by swinging her tail. The males approach upon sensing the eddies created by the female's tail. When the female begins to produce an egg sac, a male will grasp her inguinal region with his forefeet while pulling on the egg sac with his hind feet and squirting sperm over it. Often many males will take part in this activity together, forming a mating ball (Goris and Maeda 2004). During the breeding phase, males also undergo a noticeable increase in head width (Hasumi and Iwasawa 1990; Hasumi 1994).

The female lays two egg sacs which absorb water and finally take on the look of white eggplants attached to a twig or branch. A single clutch contains a total of 40-140 eggs. At low altitudes the eggs hatch in about 1 month, but may take longer at higher altitudes. The larvae feed mainly on each other, though they may also feed on aquatic insects, frog tadpoles, etc. They metamorphose and leave the water from summer to early autumn, but some may overwinter as larvae, and leave the water the following year. Outside the breeding season, juveniles and adults hide under dead leaves, fallen logs, and rocks. They become more active at night, feeding on millipedes, spiders, small insects, small land crabs, and earthworms (Goris and Maeda 2004).

Comments
In the past, the Sadogashima population has been treated as a separate species or subspecies, but the validity of this classification has been challenged (Goris and Maeda 2004).

References

Goris, R.C. and Maeda, N. (2004). Guide to the Amphibians and Reptiles of Japan. Krieger Publishing Company, Malabar, Florida.

Hasumi, M. (1994). ''Reproductive behavior of the salamander Hynobius nigrescens: monopoly of egg sacs during scramble competition.'' Journal of Herpetology, 28(2), 264-267.

Hasumi, M. and Iwasawa, H. (1990). ''Seasonal changes in body shape and mass in the salamander, Hynobius nigrescens J.'' Journal of Herpetology, 24(2), 113-118.

IUCN, Conservation International, and NatureServe. 2006. Global Amphibian Assessment. < www.globalamphibians.org >. Accessed on 28 November 2006.

Species Account Citation: AmphibiaWeb 2007 Hynobius nigrescens: Black Salamander <https://amphibiaweb.org/species/3891> University of California, Berkeley, CA, USA. Accessed Nov 22, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 22 Nov 2024.

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