Hynobius akiensis Matsui, Okawa et Nishikawa, 2019

Sugawara, Hirotaka, Naito, Jun-ichi, Iwata, Takayuki & Nagano, Masahiro, 2022, Molecular Phylogenetic and Morphological Problems of the Aki Salamander Hynobius akiensis: Description of Two New Species from Chugoku, Japan, Bulletin of the Kanagawa Prefectural Museum (Natural Science) 51, pp. 35-46 : 44-45

Hynobius akiensis Matsui, Okawa et Nishikawa, 2019

(Standard Japanese name: Aki-sanshouo)

( Fig. 4 )

Hynobius akiensis Matsui, Okawa and Nishikawa in Matsui et al., 2019: 75, in part.

Holotype. An adult male (specimen number: KUHE 35925 ) from Mirasakacho Haizuka , Miyoshi-shi , Hiroshima Prefecture, collected by Yasuchika Misawa and Kanto Nishikawa on 26 March 2005. This specimen is stored in the Graduate School of Human and Environmental Studies, Kyoto University: Yoshidahonmachi, Sakyo-ku, Kyoto-shi, Kyoto Prefecture, 606-8501, Japan.

Diagnosis. A comparatively small species (mean snout– vent length of 51.2 mm in males) within the Japanese lentic Hynobius ; distinct white dots on the ventral side of the body usually present; distinct brownish–yellow stripe on the dorsal edge of the tail usually absent; distinct brownish–yellow line on the ventral side of the tail never present; distinct gular mottling usually absent; yellowish– brown to blackish–brown on dorsum; fifth toe of hindlimb always present; V-shaped vomerine teeth series; 12 costal grooves (rarely 13); costal folds between adpressed limbs usually less than 0.5; coil-shaped egg sacs.

Description of a specimen from the type locality (Topotype). An adult male (specimen number: KPM-NFA 946) from the same locality of holotype, collected by Takayuki Iwata on 23 March 2019. A moderately large individual with HL larger than HW; TAL shorter than SVL; body almost cylindrical; rounded snout; gular fold present; tail gradually compressed toward the tip; slightly expanded cloaca; webbing between digits absent; four fingers on each forelimb, order of length II> III> IV> I in left and III> II> IV> I in right; five toes on each hindlimb, order of length III> IV> II> V> I in left and III> IV> II> I> V in right; V-shaped vomerine teeth; skin smooth and matte; DBDD absent; DWDV and DWDV present before preservation (it became unclear after preservation); DTBYLD and DTBYLV absent; DGM absent. The holotype had the following measurements (in mm): SVL = 55.3, TRL = 43.0, AGD = 27.8, HL = 12.8, TAL = 32.2, MTAW = 2.7, MTAH = 5.6, BTAW = 6.7, BTAH = 5.6, VTL = 2.6, VTW = 3.1, HW = 9.8, MXHW = 9.9, LFLL = 12.6, RFLL = 12.7, LHLL = 17.6, RHLL = 16.8, L1FL = 0.6, L2FL = 3.2, L3FL = 2.9, L4FL = 1.5, R1FL = 0.8, R2FL = 3.0, R3FL = 3.2, R4FL = 1.7, L1TL = 1.1, L2TL = 3.2, L3TL = 4.9, L4TL = 3.4, L5TL = 1.2, R1TL = 0.8, R2TL = 3.3, R3TL = 4.9, R4TL = 3.5, R5TL = 0.3, IND = 2.9, IOD = 3.3, LUEW = 1.5, RUEW = 1.7, SL = 4.0, LUEL = 2.3, RUEL = 2.4, LJL = 7.5, and CGN = 12.

Comparisons. This species is parapatrically distributed with Hynobius iwami but is distinguishable concerning for the presence of the fifth toe as well as distinct and bright yellow lines on the dorsal and ventral sides of the tail ( Matsui et al., 2019). Moreover, H. utsunomiyaorum is distributed near the range of H. akiensis but H. akiensis significantly differs from H. utsunomiyaorum by longer vomerine teeth series, fifth toe, and a greater degree of limb separation ( Matsui et al., 2019).

Variation. Morphometric measurements and observations were presented in Tables 2 and 4 , respectively. The dorsum is uniformly darkish–brown or blackish– brown. The venter is lighter than the dorsum. DBDD (8/28 = 28.6 %), DGM (6/28 = 21.4 %), and DTBYLD (3/28 = 10.7 %) are rarely present. DWDV (5/28 = 17.9 %) and DWDL (6/28 = 21.4 %) rarely absent. CGN rarely 13 (4/28 = 14.3 %), and CFBALN rarely more than 0 (3/28 = 10.7 %). The iris is dark brown. When preserved, the dorsal coloration tends to fade to dark gray.

Distribution. According to Matsui et al. (2019), this species is endemic to Hiroshima Prefecture. However, the results of our field survey do not support this finding; we show that the species is known from Hiroshima and Shimane Prefectures as follows: Mihara-shi (only former Kui-cho and Daiwa-cho), Miyoshi-shi (only former Miyoshi-shi and Mirasaka-cho, Kisa-cho, and Miwa-cho), Akitakata (former Takamiya-cho, Kodacho, Mukaihara-cho, Yoshida-cho, Yachiyo-cho, and Midori-cho), Higashihiroshima (only former Toyosakacho), and Hiroshima (only former Hiroshima-shi, Asakita-ku), and Sera-cho (only former Sera-cho and Nishisera-cho), Akiota-cho (only former Togochi-cho), and Kitahiroshima-cho(former Chiyoda-cho, Oasa-cho, Toyohira-cho, and Geihoku-cho), Hiroshima Prefecture, and Onan-cho (only former Mizuho-cho, and Hasumimura), Shimane Prefecture.

Remarks. Hynobius akiensis from Akitakata-shi and Kitahiroshima-cho is called the transition type of H. akiensis ( Okawa et al., 2019) , but the common morphological character of transition type is not defined and unclear, and a type is a polyphyletic group ( Fig. 2 ).

Figures

Fig. 4. Holotype of Hynobius geiyoensis sp. nov. (HMNH- AM-101, adult male, 58.4 mm SVL) from the (A) dorsal and (B) ventral perspective; holotype of H. sumidai sp. nov. (HMNH-AM-102, adult male, 48.2 mm SVL) from the (C) dorsal and (D) ventral perspective; and a specimen from the type locality (topotype) of H. akiensis (KPM- NFA 946, adult male, 55.3 mm) from the (E) dorsal and (F) ventral perspective.

Fig. 2. Phylogenetic tree produced by Bayesian inference using 630-bp cytochrome b genes. Salamandrella keyserlingii was used as an outgroup. Scale bar shows genetic distance (expected changes per site). Numbers located near the nodes are posterior probabilities (PP) for Bayesian inference and bootstrap (BS) values for maximum likelihood estimation. Values appearing in parentheses after the haplotype names correspond to population localities as indicated in Table 1 and Fig. 1. Asterisks after the parentheses (Pops. 1, 8, and 54) indicate the type locality of the three species.The labels covered by shaded boxes indicate the transition type of Hynobius akiensis.