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)

Hynobius nagatoensis is a moderately large lentic salamander with a male snout-vent length range of 48.9 - 65.3 mm and a female snout-vent length range of 48.1 - 66.1 mm, based on 27 males and 10 females. The body is cylindrical and the snout is rounded. The tail becomes compressed toward the tip, and its length is somewhat shorter than the snout-vent length. The head is longer than it is wide, having a head length of approximately 13.4 mm and a head width of around 11.0 mm. A gular fold is present. When appressed along the body, up to two costal grooves separate the limbs. The forelimbs are around 13.8 - 13.9 mm. There is no webbing between the four fingers. On the holotype, the finger formula is III = II < I = IV on the left hand and III < IV < I = V on the right. The hind limbs are around 19.2 - 19.4 mm. There are five toes following the toe length formula III < IV < II < I = V (Sugawara et al. 2022).

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

Hynobius nagatoensis is sister to H. bakan. Compared to H. bakan, H. nagatoensis has a longer snout-vent length, tail length, median tail height, and head width. The most distinguishing trait is the tail length to snout-vent length ratio, which is over 76% in H. nagatoensis males and usually under 76% in H. bakan males (Sugawara et al. 2022).

COLORATION: (In life and/or in preservative)

In life, the dorsum ranges from yellow-brown to black-brown, while the ventrum can be bluish-white, reddish-white, or whitish-purple. Distinct black spots are present on the dorsum. There is a distinct bright yellow line on the dorsal and ventral sides of the tail. The iris can be shades of dark to light brown. On the ventral side of the head, there is distinct gular mottling. In preservative, the dorsum fades to a dark gray (Sugawara et al. 2022).

VARIATION: (if known)

Males tend to have longer head lengths, head widths, tail lengths, median tail heights, and forelimbs than females. The number of costal grooves between adpressed limbs is lower in males (1.0 to 1.5) than in females (0 to 2.0). The distinct white spots on the venter occur more frequently in females than males, while the yellow line on the dorsal side of the tail occurs more frequently in males than females. Gular mottling is never present in females (Sugawara et al. 2022).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Japan

View distribution map in BerkeleyMapper.

Hynobius nagatoensis occurs in Shimonoseki, Mine, and Ube Cities in Yamaguchi Prefecture, Japan. The species also occurs in Moji Ward, Kitakyushu City, Fukuoka Prefecture, and has been observed in Yuya Town, Yamaguchi Prefecture. 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
Oviposition occurs on branches or leaves in puddles, ponds, or swamps at forest edges between December and April. Egg sacs are coil-shaped (Sugawara et al. 2022).

Larva
There are no claws on the fingers or toes in larvae. In the early larval developmental stages, a pair of balancers is present (Sugawara et al. 2022).

Larvae have distinct black spots on the sides of the tail (Sugawara et al. 2022).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Urbanization

Comments

PHYLOGENETIC RELATIONSHIPS:

Hynobius nagatoensis 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. The Usa-Bungotakada population is described as H. nagatoensis and the Yamaguchi group is described as H. nihoensis. Hynobius bakan and H. nihoensis form a monophyletic group that is sister to H. nagatoensis based on Bayesian inference and maximum likelihood analysis of cytochrome b mtDNA. The next most closely related clade is H. dunni (Sugawara et al. 2022).

ETYMOLOGY (Origin or explanation of scientific name):

The species name “nagatoensis” comes from the name Nagato, which the Yamaguchi Prefecture (the type locality) was formerly called (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 nagatoensis: Nagato Salamander <https://amphibiaweb.org/species/9638> University of California, Berkeley, CA, USA. Accessed Apr 15, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 15 Apr 2024.

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