Hynobius geiyoensis, Sugawara & Naito & Iwata & Nagano, 2022

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 : 39-42

Hynobius geiyoensis sp. nov.

(New standard Japanese name: Geiyo-sanshouo)

( Figs. 4–5 )

Hynobius nebulosus : Okawa et al., 1990: 50, in part.

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

Etymology. The specific name is derived from “ Geiyo.” In ancient times, the combined area of Aki (= central to the western part of Hiroshima Prefecture) and Iyo (= Ehime Prefecture), where the new species occurred, was called Geiyo.

Holotype. An adult male (specimen number: HMNH-AM-101) from Nakano , Osakikamijima-cho, Hiroshima Prefecture, Chugoku, Japan [34° 13′ N, 132° 53′ E; elevation = 150 m above sea level (a.s.l.); in all cases, datum = WGS84], collected by Jun-ichi Naito on February 23, 2019.

Paratype. An adult female (specimen number: KPM-NFA 943 ) from Harada , Osakikamijima-cho, Hiroshima Prefecture, Chugoku, Japan [34° 14′ N, 132° 52′ E; elevation = 30 m above sea level (a.s.l.); in all cases, datum = WGS84], collected by Jun-ichi Naito on 23 February 2019 . An adult male (specimen number: KPM-NFA 944 ) from the same locality as the holotype, collected by Jun-ichi Naito on February 23, 2019 .

Diagnosis. A comparatively large species (with a mean snout–vent length of 60.1 mm in males) within the Japanese lentic Hynobius : snout–vent length usually more than 50 mm; distinct white dots on the ventral side of the body always present; distinct brownish–yellow line on the dorsal edge of the tail almost always present; distinct white dots on the lateral side of the body usually present; distinct yellow stripe on the ventral edge of the tail always absent; distinct gular mottling almost always absent in males; fifth toe of hindlimb always present; V-shaped vomerine teeth series; 12 (rarely 11) costal grooves; the number of costal folds between adpressed limbs always −2 to 0.5 in males.

Description of holotype. A moderately large individual: HL larger than HW; TAL shorter than SVL; body almost cylindrical; rounded snout; gular fold present; tail gradually compressed toward the tip; clearly expanded cloaca; webbing between digits absent; four fingers on each forelimb, order of length II> III> IV> I on both sides; five toes on each hindlimb, order of length III> IV> II> I> V on both sides; V-shaped vomerine teeth; skin smooth and shiny; DBDD present; DWDV and DWDL present (it became unclear after preservation); DTBYLD present; DTBYLV absent; DGM absent. The holotype had the following measurements (in mm): SVL =58.4, TRL = 45.7, AGD = 31.6, HL = 12.5, TAL = 50.0, MTAW = 4.0, MTAH = 8.2, BTAW = 8.0, BTAH = 7.3, VTL = 3.2, VTW = 2.8, HW = 10.2, MXHW = 10.4, LFLL = 13.8, RFLL = 13.7, LHLL = 17.8, RHLL = 18.0, L1FL = 1.5, L2FL = 3.2, L3FL = 3.1, L4FL = 1.7, R1FL = 1.3, R2FL = 3.4, R3FL = 2.7, R4FL = 1.6, L1TL = 1.9, L2TL = 3.9, L3TL = 5.3, L4TL = 4.0, L5TL = 1.6, R1TL = 1.6, R2TL = 3.6, R3TL = 5.0, R4TL = 3.7, R5TL = 1.0, IND = 2.9, IOD = 3.8, LUEW = 1.6, RUEW = 1.4, SL =4.0, LUEL =2.5, RUEL = 2.7, LJL = 7.3, CGN = 12.

Comparisons. The new species statistically differs from H. akiensis in terms of the following length measurements in males: SVL, RHL, RTAL, RMTAH, RFLL, R5TL, RIOD, RUEW, RUEL, and RLJL; except for SVL, RTAL, RMTAH, and R5TL, these lengths were significantly shorter in H. geiyoensis sp. nov. relative to the lengths in H. akiensis . The new species differs from H. akiensis by the following characters: SVL> 57.1 mm (18/19 = 94.7 %) vs. SVL <57.2 mm (26/28 = 92.9 %); RUEW <3.2 % (18/19 = 94.7 %) vs. RUEW> 3.1 % (23/28 = 82.1 %); RUEL <4.2 % (17/19 = 89.5 %) vs. RUEL> 4.1 % (27/28 = 96.4 %); usually have DTBYLD (17/19 = 89.5 %) vs. usually lack DTBYLD (25/28 = 89.3 %).

Variation. Morphometric measurements and observations are presented in Tables 2 and 4 , respectively. The dorsum is uniformly yellowish brown or darkish brown. In the new species, DBDD are sometimes present (8/19 = 42.1 %), DWDL (3/19 = 15.8 %) and DTBYLD (2/19 = 10.5 %) are rarely absent, DGM is rarely present (1/19 = 5.3 %), CGN rarely 11 (2/19 = 10.5 %), and CFBALN rarely more than 0 (1/19 = 5.3 %). The iris is dark brown. When preserved, the dorsal coloration tends to fade to dark gray and DTBYLD becomes unclear after preservation.

Distribution. This new species is known from Higashihiroshima-shi (including the former Higashihiroshima-shi and Kurose-cho), Takehara-shi, and Kure-shi (including the former Kure-shi) in Hiroshima Prefecture, and Imabari-shi (including the former Imabari-shi and Namikata-cho) in Ehime Prefecture. DNA samples from the former Kurose-cho is not included in this study; however, based on previous field surveys ( Okawa et al., 1990), this species may be distributed in this area. This new species may also occur in the former Akitsucho (currently part of Higashihiroshima-shi) but there is currently no evidence to support this hypothesis. It was reported in 2018 that the populations of Kure-shi (2018) might already be extinct as. However, sufficient field surveys with objective evidences to support its extinction in Kure-shi have not been performed. Therefore, further field surveys are needed to clarify the current distribution range of the new species in greater detail.

Natural History. The dominant vegetation type of the type locality is a mixed forest of evergreen Fagaceae trees (i.e., Quercus and Castanopsis spp. ) and Japanese cedar ( Cryptomeria japonica ) ( Fig. 5 ). Larvae have distinct black dots on the lateral sides of the tail, whereas claws on the tips of the fingers and toes are absent. One pair of balancers is present during the early developmental stages of the larvae. Egg sacs are coil-shaped and are attached to fallen branches or leaves in ponds, puddles, or swamps at forest edges from February to April.

Remarks. The new species forms a monophyletic group with the Highland and Aki groups ( Matsui et al., 2019). The morphology of females is unclear; thus, further studies to clarify female morphology are required.

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. 5. Larvae, egg sacs, and habitat at the type locality of Hynobius geiyoensis sp. nov. (A, C, and E, respectively) and H. sumidai sp. nov. (B, D, and F, respectively).