Description
Onychodactylus kinneburi is a thick, elongated, cylindrical-bodied salamander with a snout-vent length range in males of 59.2 – 78.5 mm and in females of 64.2 – 88.9 mm. The head is oval-shaped, depressed, and longer than it is wide. The rounded snout projects past the lower jaw, and the nostrils are closer to the eyes than the tip of the snout. The eyes protrude laterally slightly over the upper jaw and are larger than the length of the snout. The well-developed, oval parotoid gland runs from the angle of the jaw to the gular fold. There is also an obvious postorbital groove on the head that connects to the gland. The neck is slightly narrower than the head. The forearm is slightly thicker than the upper arm. The relative length of the fingers is I < IV < II < III. The hind limb is longer than the thin forelimb and the tibia is slightly thicker than the thigh. There is a well-developed dermal flap on the posterior edge of hind limb. The relative length of toes is I < V < II < III < IV. All of the digits have horny claws on the tips. During the breeding season, tubercles and asperites can be found on the palms of males and soles of the feet of both sexes. There is an indistinct middorsal groove from end of head to cloacal region, and 12 - 14 well developed costal grooves. The base of the tail is swollen, and the slightly swollen cloaca forms an inverse V-shaped fold in males and an inverse U-shape in females lined by small spines on the anterior edge. The long tail is about 129% of the snout-vent length and has a cylindrical base that compresses laterally towards the rounded tip (Yoshikawa et. al. 2013).

Immediately after hatching, at stages 54 and 55, larvae have a total length of 27 - 27.3 mm and a snout-vent length of 14.9 – 15.3 mm. They have a large yolk, undeveloped spatulate limbs. At stages 66 – 70, larvae have snout vent lengths of 17.9 – 53.1 mm and total lengths of 32.9 - 105.3 mm. They have rectangular heads with a blunt snout, a developed labial fold on the upper jaw, prominent eyes, and three pairs of short external gills. There are skin folds on the poster edge of the limbs. The palms and soles of the feet, like adults, have asperities and the digit tips have curved claws. The tail has a moderately rounded tip and low caudal fins that are well developed, with the dorsal fin larger than the ventral fin. The dorsal fin begins at the level of the posterior hind limb and cloaca region. The ventral fin starts two thirds to half the length of the tail from the tip (Yoshikawa et. al. 2013).

Onychodactylus kinneburi can be differentiated from O. fischeri, O. koreanus, O. zhangypingi and O. zhaoermii, by locality (Japan vs. continental Asia) and by the former’s distinct wide dorsal stripe. The focal species can by further differentiated from O. fischeri by the former having a smaller snout-vent length, relatively shorter tail, longer limbs, wider head, wider internarial space, fewer presacral veterbrate, fewer costal grooves, and more vomerine teeth. A larger snout-vent length, shorter tails in males, narrower head, and fewer vomerine teeth in O. kinneburi help differentiate it from O. koreanus. Onychodactylus kinneburi has a larger snout-vent length, relatively shorter tail, shorter trunk in males, and fewer vomerine teeth in males than O. zhangypingi. Onychodactylus kinneburi also has a larger snout-vent length and relatively shorter tail than O. zhaoermii. They can also be differentiated by the former having more presacral vertebrae, more costal grooves, and more vomerine teeth in females. From members of the O. japonicus species complex (O. japonicus, O. nipponoborealis, and O. tsukubaensis), O. kinneburi can be differentiated by having a larger snout-vent size. More specifically, O. kinneburi has longer hind limbs in females, shorter snouts, narrower intercanthal spaces in males, more presacral vertebrate, and more costal grooves than O. japonicus. Differentiation based on coloration is more difficult as some populations of O. japonicus also have wide dorsal stripes. However, the two species can still be differentiate by O. kinneburi having a yellowish instead of red strip and lack a wedge shaped dark marking on the neck and chest. Onychodactylus kinneburi has a significantly shorter tail and hind limbs in males, longer trunk and narrower head in females, narrower chest, shorter snout, more presacral verterbrae, and more costal grooves than O. nipponoborealis. They can also be differentiated by O. kinneburi having a yellow to yellowish-orange dorsal stripe on a gray-brown to black background instead of O. nipponoborealis’s ochre to brown stripe on a dark-brown blackground with silver dots. Lastly, O. kinneburi has a significantly longer tail, longer trunk and shorter, narrower heads in females, narrower chest, more presacral vertebrate, and more costal grooves than and O. tsukubaensis. Similar to O. nipponoborealis, O. tsukubaensis has an ochre to reddish-brown stripe on a greyish-brown body with silver dots (Yoshikawa et. al. 2013).

Larval O. kinneburi are almost indistinguishable to O. japonicas. An orange-ish dorsal stripe or blotches on a uniformly black background differentiates O. kinneburi from O. tsukubaensis and O. nipponoborealis. A longer tail also distinguishes O. kinneburi from O. tsukubaensis (Yoshikawa et. al. 2013).

In life, O. kinneburi has a red-orange to yellow-orange to light yellow dorsal strip extending from snout to tail tip against gray-brown to dark-gray or black background. The stripe can be straight, wavy, continuous, to discontinuous mottling. The dorsal coloration fades gradually to an unmarked, white ventrum. There may be small yellow-orange spots on the lateral side. The upper half of the iris is dark brown with some mottled gold and the lower half is uniformly dark-brown. The claws and asperities on the hands are black. In alcohol, the yellow coloration bleaches to become white dorsal patterning (Yoshikawa et. al. 2013).

In life, hatchlings are either yellow-gray with black spots on the dorsum, or black with sharply edged wide stripe. Hatchlings have a white or transparent ventrum. Older, premetamorphic larvae have an orange dorsal stripe or mottling on black background that runs from their head to the their tail, and an unmarked white or gray ventrum (Yoshikawa et. al. 2013).

There are morphological variations in this species based on geography, sex, breeding condition, and individual variation. Geographically, the Honshu populations are generally shorter than their Shishoku counterparts with shorter tails and male anterior limbs. Honshu individuals also have larger eyes in females. Sexually, males are smaller than females but have longer tails, taller basal and medial tail height, wider basal and medial tail width, shorter trunks, shorter hind limbs, longer heads, larger eyes, larger internarial distance, fewer vomerine teeth, and more robust hind limbs with projecting distal ends of the fibula. Males also have secondary sexual characters that are only present when they are in breeding condition. Only breeding adults possess a dermal skin fold on the hindlimb (males only), swollen cloaca (males only), black claws on digits, black tubercles and asperites, swollen parotoid glands, precloacal skin fold (V-shaped for males, U-shaped for females), black precloacal spine series, and laterally well-compressed tail. Lastly, the number of costal grooves varies from 12 - 14, and presacral vertebrae from 18 - 20 in individuals. The dorsal stripe also varies in shape from straight, wavy, continuous, to discontinuous mottling, and the color varies from red-orange to light yellow. The background can range from gray-brown to dark-gray or black, and there are sometimes small yellow-orange spots on the lateral side (Yoshikawa et. al. 2013).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Japan

View distribution map in BerkeleyMapper.

Onychodactylus kinneburi can be found in western Japan, on Shikoku Island and in some parts of Chugoku Mountains of western Honshu. Its eastern limit is Mt. Tsurugi, Tokushima Prefecture, its southwestern limit is in Uchiko-cho, Ehime Prefcture. In western Honshu, the species can be found in two disjoint localities, the first being around Kagamino-cho, Okayama Prefecture and at Mts. Jippo and Kanmuri, Hatsukaichi-shi in Hiroshima Prefecture and the second being Mt. Jakuchi, Iwakuni-shi in Yamaguchi Prefecture. The species inhabits mountain streams and cool, humid forests 700 m and higher above sea level (Yoshikawa et. al. 2013).

Life History, Abundance, Activity, and Special Behaviors
Little is known about non-breeding adult O. kinneburi except that they inhabit well-forested cool, humid mountainous areas. Adults are found under stones, rocks, and logs on the forest floor away from streams. They are locally abundant, but have a limited range (Yoshikawa et. al. 2013).

The breeding season runs from mid-May to mid-June, when adults arrive at breeding sites near flowing headstreams, which may be underground on the upper parts of the mountains. They attach egg sacs to the undersides of rocks with gelatinous stalks up to 20 mm in length in cold streams of 6 – 9^oC. The egg sacs have a transparent tough, but elastic, outer layer, are cylindrical or spindle in shape with eggs arranged in one or two rows respectively. Eggs are large (4.7 – 5.9 mm diameter) and white or yellow-white in color. Clutch size ranges from 2 – 25 (Yoshikawa et. al. 2013).

Hatchlings are generally not found in open streams. However, after some development, the larvae at sizes 32.9 to 105.3 mm disperse downstream where they grow for two or more years before metamorphosis. Metamorphosis is reported to occur in late summer-early autumn, after which juveniles live on the forest floor around the stream (Yoshikawa et. al. 2013).

Onychodactylus kinneburi inhabits the Chugoku mountains sympatrically with O. japonicus. The breeding season and sites are identical despite genetic isolation (Yoshikawa et. al. 2013).

They are predated on by the snake Rhabdophis tigrinus (Yoshikawa et. al. 2013).

Trends and Threats
Onychodactylus kinneburi is locally abundant but has a limited and fragmented range. The species is locally listed as “Vulnerable” because of habitat disturbances from deforestation, road and dam construction. Additionally, because the species utilizes open and underground streams for breeding, management of the habitats is necessary to conserve the species. At the time of the species’ description, the authors proposed an IUCN listing of “Near Threatened” (Yoshikawa et al. 2013).

Relation to Humans
The species is collected for medicine (Yoshikawa et. al. 2013).

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Dams changing river flow and/or covering habitat
Habitat fragmentation

Comments
The species authority is: Yoshikawa, N. N., Matsui, M., Tanabe, S., and Okayama, T. (2013). “Description of a new salamander of the genus Onychodactylus from Shikoku and Western Honshu, Japan (Amphibia, Caudata, Hynobiidae).'' Zootaxa, 3693, 441-464.

Based on Maximum Likelihood analysis of cytB mtDNA sequences, O. kinneburi is the sister taxa to members of the Onychodactylus sp. Kinki group. Together, this clade is sister to O. japonicus (Yoshikawa et. al. 2013).

Despite having a disjointed range, the two major populations of O. kinneburi have no significant genetic differences. Additionally, although O. japonicus share breeding time and site with O. kinneburi in western Honshu, the two species are genetically distinct and reproductively isolated from each other based on both mitochondrial and nuclear DNA (Yoshikawa et. al. 2013).

The species name “kinneburi” is derived from “kin-neburi”, a local name for the salamander meaning “gold licker”. This name could be based on the gold markings, the high price they fetch in the medical trade, or the local belief that the salamanders go underground to lick gold (Yoshikawa et. al. 2013).

References

Yoshikawa, N. N., Matsui, M., Tanabe, S., Okayama, T. (2013). ''Description of a new salamander of the genus Onychodactylus from Shikoku and western Honshu, Japan (Amphibia, Caudata, Hynobiidae).'' Zootaxa, 3693(4), 441-464. [link]

Species Account Citation: AmphibiaWeb 2019 Onychodactylus kinneburi: Shikoku clawed salamander; Shikoku-hakone-sanshou-uwo <https://amphibiaweb.org/species/8041> University of California, Berkeley, CA, USA. Accessed Dec 11, 2023.

Citation: AmphibiaWeb. 2023. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 11 Dec 2023.

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