Hynobius oyamai, Tominaga & Matsui & Nishikawa, 2019

Tominaga, Atsushi, Matsui, Masafumi & Nishikawa, Kanto, 2019, Two new species of lotic breeding salamanders (Amphibia, Caudata, Hynobiidae) from western Japan, Zootaxa 4550 (4), pp. 525-544 : 533-542

Hynobius oyamai n. sp.

(Japanese name: Chikushi-buchi-sanshou-uwo)

( Figs. 4C, D , 5B , 6B , 7C, D, E )

Pseudosalamandra naevia: Tago 1931: 170 –180, pl. XX. (part).

Hynobius naevius: Abe 1922: 329 -330 (part); Sato 1943: 198 –217 (part).

H. naevius (part, Type A): Tominaga et al. 2003: 1467.

Hynobius naevius (part Group A): Tominaga et al. 2005a: 921; Tominaga et al. 2005b: 1229, fig. 7C.

Hynobius naevius (part northeastern Kyushu subclade in Clade 2): Tominaga et al. 2006: 677.

Holotype: KUHE 27267 ( Fig. 4C, D ), an adult male from Hatake, Yahatanishi-ku, Kitakyushu-shi , Fukuoka Prefecture (33 o 47’52”N, 130 o 47’42”E, alt. 310 m) collected by A. Tominaga on 15 May 2000.

Paratypes: All from Kitakyushu-shi, Fukuoka Prefecture : KUHE 12984–12988 , 3 males 2 females from Kawachi, Yahatahigashi-ku by Y. Misawa on 6 April 1992 ; KUHE 16746–16752 , 7 males from Kawachi, Yahatahigashi-ku by Y. Misawa on 27 February 1994 ; KUHE 22798–22801 , 1 male and 3 females from Kawachi, Yahatahigashi-ku by Y. Misawa and K. Nishikawa on 30 March 1997 ; KUHE 27281 , 1 male from Kawachi, Yahatahigashi-ku by A. Tominaga on 15 May 2000 ; KUHE 28379–28383 , 5 males from Kawachi, Yahatahigashiku by A. Tominaga on 25 February 2001 ; KUHE 28496 , 1 male from Kawachi, Yahatahigashi-ku by A. Tominaga on 24 March 2001 ; KUHE 28579–28581 , 3 males from Hatake, Yahatanishi-ku by A. Tominaga on 18 April 2001 ; KUHE 29959 , 1 male from Hatake, Yahatanishi-ku by A. Tominaga on 31 March 2002 ; Mr. Tanabe private collection T2400, from Hanao-cho, Yahatahigashi-ku collected by S. Tanabe on 5 May 1992.

Referred specimens: KUHE 26857–26858, 26860, 27282, 27283, 27807, 27883–27884, 27900, 27904, 28372, 28487, 28488, 28577, 28578, 28673, 28674, 28955–28957, 29364 from Asakura-shi, Fukuoka Prefecture. KUHE14387–14390, 29986, 32578–32582 from Kunisaki-shi, Oita Prefecture; KUHE 13608–13610, 14391– 14392, 26144–26147, 27561, 29982–29984, 32584 from Kokonoe-cho, Oita Prefecture.

Etymology: The specific name " oyamai " is dedicated to the late Dr. Junji Oyama of Kyushu Imperial University (current Kyushu University), who made great contributions to the study of Japanese salamanders especially in Kyushu.

Diagnosis: A large species (adult SVL 65–89 mm in males and 71–86 mm in females) within the lotic breeding Hynobius ; dorsum usually immaculate in adults; limbs and tail long; tips of fore- and hindlimbs adpressed on body never meeting (overlap of -3.0 to -0.5 costal folds in males and -3 to - 1.5 in females); fifth toe well developed; ova large, pigmentless; egg sacs short and crescent-like, without distinct whiptail structure on free end; most similar to H. naevius , but distinct from it by wider head, longer lower jaw, longer snout, wider internarial, wider upper eyelid, longer hindlimb, longer third finger, and third and fifth toes, and wider but shallower vomerine teeth series, all relative to SVL, and sometimes by presence of pale white dorsal marking on the trunk.

Description of holotype (measurements in mm): Head-body medium (SVL 69.1) but robust; head oval and moderately depressed, distinctly longer (HL 16.0, 23.2%SVL) than wide (HW 12.7, 18.4%); snout rounded, slightly projecting beyond lower jaw; nostril close to snout tip; labial fold absent; eye large, prominently protruded, slightly inset from edge of head in dorsal view; upper eyelid well developed (UEW 2.3, 3.3%SVL), shorter (UEL 3.9, 5.6%SVL) than snout (SL 4.7, 6.8%SVL); gular fold distinct, curving slightly anteriorly; parotoid gland evident, extending from angle of jaw to gular fold; postorbital grooves distinct, branching posterior to angle of jaw, one short and running down to lower jaw, the other long and posteriorly to gland; vomerine teeth series slightly wider (VTW 3.5, 5.1%SVL) than long (VTL 2.9, 4.3%SVL), vomerine teeth shallow V-shaped, series nearly touching at midline ( Fig. 5B ), tongue broad, both sides free from mouth floor; fore- and hindlimbs long and thick (FLL 16.2, 23.4%SVL; HLL 20.2, 29.2%SVL); number of costal grooves between axilla and groin 13; depressed limbs separated by one and half costal folds; relative length of fingers I<IV<III<II, toes I<V<II<IV<III; fifth toe well developed (5TL 1.8, 2.6%SVL); cloaca longitudinal slit; genital tubercle on anterior cloaca absent; tail short (TAL 46.6, 67.4%SVL), cylindrical at base (BTAW 7.3, 10.6%SVL; BTAH 6.8, 9.8%SVL), increasingly compressed posteriorly, caudal fin poorly developed posteriorly; tip of tail rounded in lateral view.

Additional Measurements and counts of the holotype: IND (3.8, 5.5%SVL); IOD (4.0, 5.8%SVL); AGD (35.9, 52.0%SVL); TRL (53.1, 76.9%SVL); MTAW (5.4, 7.8%SVL); MXTAH (7.6, 11.00%SVL); MTAH (7.2, 10.4%SVL), 2FL (3.0, 4.3%SVL); 3FL (2.8, 4.1%SVL); 3TL (4.5, 76.5%SVL); UJTN (77); LJTN (81); VTN (45).

Color: In life, dorsum bluish-purple in ground color, without marking ( Fig.4C ) but sometimes with discontinuous, pale white markings. Underside of body lighter than dorsum with light white marking ( Fig. 4D ). The ground color of ventral side becoming bluish gray with relatively large markings varying from pale white to white. In preservative, dorsal and ventral ground color tending to fade.

Variation: Morphometric data are summarized in Table 1. Males tended to have relatively wider head (HW, median=17.9%SVL) than in females (17.3%SVL). Males had relatively longer forelimb (median=24.1%SVL) and hindlimb (median=30.0%SVL) than in females (median=22.2%SVL and 28.7%SVL, respectively). Separation of limbs was greater in females (median=2.5 folds) than in males (median=1.5 folds). Males had relatively longer (median=73.8%SVL) and higher (median=11.4%SVL) tail than in females (median=68.5%SVL and 9.8%SVL, respectively). Third toe was usually longer than fourth. Fifth toe was almost always present.

Eggs and egg sacs: The egg sac morphology of Hynobius oyamai n. sp. is shown in Fig. 6B . Egg sacs are crescent in shape with slightly thin envelope, and lack a distinct whiptail structure on the free end. The clutch size is small, ranging from 17–55 (mean ± SD =25.8 ± 7.1, n = 33). The diameter of ova from four females are 5.1–5.6 (mean ± SD = 5.3 ± 0.16, n = 18) mm, 4.9–5.4 (mean ± SD = 5.1 ± 0.14, n = 10) mm, 5.4–6.3 (mean ± SD = 5.7 ± 0.29, n = 10) mm, and 4.7–5.1 (mean ± SD = 4.8 ± 0.12, n = 10) mm. Both the animal and the vegetal poles are cream in color.

Larva e: Fully grown larvae (n = 20) at St. 61–64 (median = 63) of Iwasawa and Yamashita (1991) of the first year in early August had SVL ranging from 20.6–32.4 (mean ± SD =25.9 ± 3.2) mm and total length of 42.4–63.5 (mean ± SD = 50.9 ± 5.8) mm, head rounded in dorsal and lateral views ( Fig. 7C, D ); snout short and broadly rounded; eyes slightly protruded, inset from edge of head in dorsal view; labial fold distinct at half of upper jaw; external gills developed; caudal fin higher than head; dorsal fin higher than ventral fin; origin of dorsal fin at half of trunk; ventral fin originating from vent; tail tip weakly pointed; limbs slender; claws on fingers and toes absent. In life, dorsum light brown with marking; venter whitish and transparent ( Fig. 7E ); small black marking; golden dots scattered on tail fin. In preservative, dorsal coloration tending to fade and golden dots fading to white.

Range: Known from mountain regions of northeastern Kyushu district, Western Japan, in Fukuoka, Kumamoto, and Oita Prefectures. ( Fig. 1 ). Hynobius oyamai n. sp. is sympatrically distributed with H. stejnegeri . Whereas, Hynobius oyamai n. sp. is allopatrically distributed with H. naevius , H. shinichisatoi , H. amakusaensis , H. osumiensis , and H. ikioi in Kyushu ( Tominaga et al. 2003; Nishikawa & Matsui 2014; Matsui et al. 2017).

Morphological comparisons: Hynobius oyamai n. sp. is distinct from all lentic breeding species of Hynobius by having the tail cylindrical at base, and large, unpigmented eggs, small in number per clutch. Hynobius oyamai n. sp. is most similar to H. naevius morphologically, but is distinguished from the latter by larger number of upper and lower jaw teeth, relatively wider head, longer lower jaw, longer snout, wider internarial and upper eyelid, longer hindlimb, third finger, and third and fifth toes, and wider but shallower vomerine teeth series, and sometimes by the presence of pale white dorsal marking on their trunk. Hynobius oyamai n. sp. is distinguished from H. sematonotos by larger body size, greater degree of limb overlap, and larger number of upper and lower jaw, and vomerine teeth. It also has smaller upper eyelid, longer trunk, shorter hindlimb, longer fifth toe, and moderately deeper vomerine teeth series, all relative to SVL than H. sematonotos . Additionally, H. oyamai n. sp. sometimes differs from the latter by the absence of dorsal marking. Hynobius oyamai n. sp. is also distinguishable from other Japanese lotic breeding congeners, including H. hirosei and H. katoi , by the presence of pale white to white ventral and dorsal markings on the trunk. Hynobius oyamai n. sp. is also distinct from H. hirosei by smaller body size (64.8–88.5 mm vs. 73.3–103.3 mm in H. hirosei ), relatively shorter head length (RHL: 21.0–24.8%SVL vs. 23.8–28.6%SVL in H. hirosei ), relatively narrower internarial distance (RIND: 5.0–6.4%SVL vs. 5.3–7.5%SVL in H. hirosei ), relatively smaller upper eyelid width (RUEW: 2.8–3.7%SVL vs. 3.3–4.7%SVL in H. hirosei ), relatively longer axilla-groin distance (RAGD: 50.6–57.1%SVL vs. 46.9–55.2%SVL in H. hirosei ), relatively longer trunk length (RTRL: 75.2– 79.0%SVL vs. 71.4–76.3%SVL in H. hirosei ), and relatively smaller vomerine teeth series width (RVTW: 4.3– 6.0%SVL vs. 5.0–7.7%SVL in H. hirosei ) ( Nishikawa et al. 2007). Hynobius oyamai n. sp. is also distinct from H. katoi by larger body size (64.8–88.5 mm vs. 53.8–66.1 mm in H. katoi ), relatively shorter head length (RHL: 21.0– 24.8%SVL vs. 24.0–25.2%SVL in H. katoi ), relatively larger head width (RHW: 15.8–19.2%SVL vs. 14.8– 16.7%SVL in H. katoi ), and relatively longer trunk length (RTRL: 75.2–79.0%SVL vs. 74.8–76.0%SVL in H. katoi ) ( Matsui et al. 2004). From all Taiwanese species that are lotic breeders, H. oyamai n. sp. differs by larger body size (SVL less than 69 mm [ Lai & Lue 2008]) and different coloration.

Natural history: Breeding occurs from March to early June and egg sacs are attached to stones under the water in mountain streams with the maximum width of 2 m. Larvae feed in the stream and usually metamorphose in autumn at a medium size (SVL = 23.4–26.4 mm). Some overwintered larvae can be found in spring. Breeding site and larval life of Hynobius oyamai n. sp. is similar to those of other allopatric lotic breeding salamanders of Kyushu ( H. naevius , H. shinichisatoi , H. amakusaensis , H. osumiensis , and H. ikioi ) but differ from those of sympatric H. stejnegeri which breed in very small headstreams under the ground where larvae hatch from large eggs with large amount of yolks and develop without feeding and metamorphose at a small body size (SVL = 19.3– 19.7mm) ( Tominaga et al. 2003).

Figures

FIGURE 1. Map of western Japan and distributional range of Hynobius naevius and two new species. Range filled by oblique lines: distributional range of H. naevius; range filled by horizontal line: distributional range of H. sematonotos n. sp.; range filled by vertical lines: distributional range of H. oyamai n. sp. Closed symbols: sampling locality used in this study. Closed triangle: supposed type locality and sampling locality of topotypic specimens of H. naevius. Closed star: type locality of H. sematonotos n. sp. Closed diamond: type locality of H. oyamai n. sp.

FIGURE 4. Dorsal and ventral views of male holotype (KUHE 30218) of Hynobius sematonotos n. sp. A, B), male holotype (KUHE 27267) of Hynobius oyamai n. sp. (C, D), and supposed topotypic male specimen (KUHE 28637) of H. naevius from Tara-cho, Saga Prefecture. Scale bar shows 50 mm.

FIGURE 5. vomerine teeth series of male holotype (KUHE 30218) of Hynobius sematonotos n. sp. (A), male holotype (KUHE 27267) of Hynobius oyamai n. sp. (B), and supposed topotypic male specimen (KUHE 28637) of H. naevius (C) from Taracho, Saga Prefecture. Scale bar indicates 1 mm.

FIGURE 6. Egg sacs of Hynobius sematonotos n. sp. from Shobara-shi, Hiroshima Prefecture (A) and egg sacs of Hynobius oyamai n. sp. from Yamaga-shi, Kumamoto Prefecture (B). Scale bar in (B) shows 5 cm.

FIGURE 7. Dorsal (A) and lateral (B) views of a full-grown larva (Stage 62) of Hynobius sematonotos n. sp. from Higashihiroshima-shi, Hiroshima Prefecture (type locality). Dorsal (C), lateral (D), and ventral (E) views of a full-grown larva (Stage 63) of Hynobius oyamai n. sp. from Kitakyushu-shi, Fukuoka Prefecture (type locality). Scale bar shows 10 mm.