AmphibiaWeb - Hynobius nihoensis


(Translations may not be accurate.)

Hynobius nihoensis Sugawara, Nagano & Nakazono, 2022
Niho-sanshōuo, Niho salamander (Japanese 二豊サンショウウオ)
family: Hynobiidae
subfamily: Hynobiinae
genus: Hynobius
Species Description: Sugawara H, Tahara Y, Nakazono S, Matsukoji T & Nagano M. 2022. Taxonomic revision of the Yamaguchi salamander Hynobius bakan: Description of two new species from Chugoku and Kyushu, Japan. Science Report of the Yokosuka City Museum(69): 1-17.
Conservation Status (definitions)
IUCN Red List Status Account
National Status None
Regional Status None


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Hynobius nihoensis is a lentic salamander with a male snout-vent length range of 41.6 - 70.3 mm and a female snout-vent length range of 56.0 - 62.9 mm. The head is longer than it is wide. The gular fold is present. The body is nearly cylindrical and the skin is matte and smooth. There are 12 - 14 costal grooves, but most often 13. The number of costal grooves that are overlapped between adpressed limbs is 4.5 to 1.5 for males and 4.5 to 2.5 for females. There are four fingers on each forelimb with no webbing, and an order of relative finger length of II < III < IV < I. There are five toes on each hind limb with a length formula of III < IV < II < V < I. The tail is shorter than the snout-vent length and becomes more compressed toward the tip (Sugawara et al. 2022)

Compared to other Hynobius salamanders in Japan, H. nihoensis has a shorter snout-vent length. Hynobius nihoensis and H. nagatoensis are both described from populations previously thought to be of H. bakan (see Comments). Hynobius nihoensis, H. bakan, and H. nagatoensis can most easily be distinguished by the number of costal grooves between adpressed limbs. The number of costal grooves between limbs for H. nihoensis is -4.5 to -1.5 for males and -4.5 to -2.5 for females; -1.0 to 1.0 in H. bakan males and -1.0 to 0.0 in females; and -1.0 to 1.5 in H. nagatoensis males and -2.0 to 0.0 in H. nagatoensis females. Hynobius nihoensis also has a smaller head width to snout-vent length ratio in both males and females compared to H. bakan. For H. bakan, this ratio is generally 17% or higher in males and 16.5% or higher in females. Hynobius nihoensis males usually have a head to snout-vent length ratio below 17% and below 16.5% for females (Sugawara et al. 2022).

In life, the dorsum ranges from yellow- to black-brown, and the ventrum can vary between blue-white, red-white, or white-purple. Females always have white spots on the ventrum and usually have a distinct yellow line on the dorsal surface of the tail. Individuals can also have black spots on the dorsum, distinct white spots on the venter, bright yellow lines on the dorsum and venter, and gular mottling, however, these were all lacking in the male holotype (see more variation below). The iris color ranges from dark to light brown. In preservative, the dorsum fades to a dark gray color (Sugawara et al. 2022).

There is some variation in patterning by sex. Black spots on the dorsum rarely occur in females. Gular mottling rarely occurs in males. Males rarely lack distinct white spots on the venter and bright yellow lines on the venter. Bright yellow lines on the dorsum are often absent in males but rarely absent in females (Sugawara et al. 2022).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Japan

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The distribution of H. nihoensis is between Bungotakada and Usa Cities in Oita Prefecture, Kyushu, Japan. The type locality is Yamashita, Usa City, Oita Prefecture, Kyushu, Japan at an elevation of 40 m a.s.l. The habitat primarily consists of mixed forest with chinquapin, live oak, and Japanese cedar (Sugawara et al. 2022).

Life History, Abundance, Activity, and Special Behaviors
Egg sacs are deposited at forest edges between January and March. Egg sacs are long, coil-shaped, and attached to fallen branches, leaves, or stones located in brooks, ponds, puddles, or swamps (Sugawara et al. 2022).

Hynobius nihoensis larvae are similar to those of H. nagatoensis (Sugawara et al. 2022).

Trends and Threats
The habitat of H. nihoensis is fragmented and near areas under development, making the small populations unsustainable. These populations are vulnerable to catastrophe and human activities like deforestation (Sugawara et al. 2022).


Hynobius nihoensis is described from a population previously thought to be H. bakan. Later analysis found that H. bakan could be divided into at least three groups: the Yamaguchi group, the Usa-Bungotakada population of the Oita group, and the Ube population of the Oita group. However, the Usa-Bungotakada population was later described as H. nagatoensis and the Yamaguchi group was described as H. nihoensis. Hynobius bakan forms a monophyletic group with H. nihoensis based on Bayesian inference and maximum likelihood analysis of cytochrome b mtDNA. The next most closely related clade is H. nagatoensis, and the clade formed by these three species is sister to H. dunni (Sugawara et al. 2022).

The species epithet, "nihoensis," comes from “Niho”, which was where the ancient provinces of Buzen and Bungo met (both of which are located in the modern-day Oita Prefecture). The current city of Usa is where the Buzen area used to be, while Bungotakada City is located where Bungo used to be. The area formerly known as Niho, which is where H. nihoensis occurs, is the boundary between Usa and Bungotakada Cities (Sugawara et al. 2022).

Sugawara, H., Y. Tahara, S. Nakazono, T. Matsukoji, and M. Nagano. (2022). Taxonomic revision of the Yamaguchi Salamander Hynobius bakan: Description of two new species from Chugoku and Kyushu, Japan. Science Report of the Yokosuka City Museum 69, 1–17. [link]

Originally submitted by: Madeline Ahn (2023-09-12)
Description by: Madeline Ahn (updated 2023-09-12)
Distribution by: Madeline Ahn (updated 2023-09-12)
Life history by: Madeline Ahn (updated 2023-09-12)
Larva by: Madeline Ahn (updated 2023-09-12)
Trends and threats by: Madeline Ahn (updated 2023-09-12)
Comments by: Madeline Ahn (updated 2023-09-12)

Edited by: Ann T. Chang (2023-09-12)

Species Account Citation: AmphibiaWeb 2023 Hynobius nihoensis: Niho-sanshōuo <> University of California, Berkeley, CA, USA. Accessed Jul 21, 2024.

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Citation: AmphibiaWeb. 2024. <> University of California, Berkeley, CA, USA. Accessed 21 Jul 2024.

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