Description
Hynobius katoi has a uniformly dark brown dorsum in life, very occasionally scattered with silvery dots. The dorsal silvery dots are seen more frequently in juveniles than in adults. The underside is lighter than the dorsum, with silvery dots also on the throat and sometimes on the belly. In preservative, the dorsal color tends to fade to gray brown. The head is moderately depressed, distinctly longer than broad. There are usually 13 costal grooves (including the axillary groove), but sometimes only 12. Limbs are short and stout. When the fore- and hindlimbs are adpressed there is almost always a space of at least 1 fold between the toes. The degree of separation is greater in females (median= 2.5 folds) than in males (median=0.75 fold). The fifth toe is very short, rudimentary, or even absent. The tail is rounded at the base and gradually flattens to the tip, becoming obtusely pointed at the tip. The tail is only slightly keeled. The upper keel very weakly originates at the posterior two-fifth and the lower keel at the posterior one-fifth. There is no development of a tail fin even in breeding males. Vomerine teeth are in two small, obliquely arched series which nearly touch at midline, usually forming a shallow "U." The combined series is wider than long. Male SVL is 58 mm and female SVL is 63 mm.

H. katoi is most similar to H. naevius in general body proportion, but with a nearly immaculate dorsum, relatively narrower head, shorter trunk, fewer vomerine teeth, and a much more shallowly curved vomerine teeth series. H. katoi is completely different from sympatric H. kimurae in having a much smaller, nearly immaculate body, longer head, shorter trunk, fewer vomerine teeth, and a much shallower vomerine teeth series.

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Japan

View distribution map in BerkeleyMapper.

H. katoi is known so far only from south Central Japan. It is found in the montane region of the northwestern part of Shizuoka Prefecture and southeastern part of Nagano Prefecture, on the Akaishi Mountains and along Oi-gawa and Tenryu-gawa rivers. The 21 known localities range from 500 meters to 1200 meters in altitude (median=750 meters).

Life History, Abundance, Activity, and Special Behaviors

Hynobius katoi belongs to the family Hynobiidae, which is one of only two salamander families exhibiting external fertilization of eggs. However, the natural history of H. katoi is poorly understood, and egg sacs or larvae have yet to be found in nature despite extensive field surveys. It is thought that breeding occurs in flowing water underground. Ovaries were examined from two collected females with 9 and 13 eggs respectively. The mean diameter of ova found in the ovaries from these two females were 4.8 and 5.0 mm. Both the animal and the vegetal poles of eggs were cream-colored. Because females with ripe eggs were collected from late April to early May, it is thought that breeding occurs in spring. The smallest young, collected in late August, is considered to have just metamorphosed. In some larvae metamorphosis seems to occur in the year of oviposition.

Comments
The specific name "katoi" is dedicated to Prof. Makoto Kato of Kyoto University who first collected this species as an undergraduate.

References

Matsui, M., Kokuryo, Y., Misawa, Y., and Nishikawa, K. (2004). ''A new species of salamander of the genus Hynobius from central Honshu, Japan (Amphibia, Urodela).'' Zoological Science, 21, 661-669.

Species Account Citation: AmphibiaWeb 2007 Hynobius katoi: Akaishi sansho-uo <https://amphibiaweb.org/species/6292> University of California, Berkeley, CA, USA. Accessed Nov 7, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 7 Nov 2024.

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