Description

DESCRIPTION: (A description of species morphology as if you had the amphibian in your hand, typically starting with the snout-vent length, then focusing from the head to the body and extremities)

DIAGNOSIS: (How this species is differentiated from similar species)

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).

COLORATION: (In life and/or in preservative)

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).

VARIATION: (if known)

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

View distribution map in BerkeleyMapper.

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).

Larva
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).

Comments

PHYLOGENETIC RELATIONSHIPS:

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).

ETYMOLOGY (Origin or explanation of scientific name):

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).

OTHER INTERESTING INFORMATION:

References
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]

Species Account Citation: AmphibiaWeb 2023 Hynobius nihoensis: Niho-sanshōuo <https://amphibiaweb.org/species/9639> University of California, Berkeley, CA, USA. Accessed Apr 19, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 19 Apr 2024.

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