Hynobius guttatus, Tominaga & Matsui & Tanabe & Nishikawa, 2019

Tominaga, Atsushi, Matsui, Masafumi, Tanabe, Shingo & Nishikawa, Kanto, 2019, A revision of Hynobius stejnegeri, a lotic breeding salamander from western Japan with a description of three new species (Amphibia, Caudata, Hynobiidae), Zootaxa 4651 (3), pp. 401-433 : 415-417

publication ID	https://doi.org/ 10.11646/zootaxa.4651.3.1
publication LSID	lsid:zoobank.org:pub:0C85653A-911A-44C6-A4BD-38F680B6199A
persistent identifier	https://treatment.plazi.org/id/C87A88C5-DA94-418F-B150-AE0F7C70990C
taxon LSID	lsid:zoobank.org:act:C87A88C5-DA94-418F-B150-AE0F7C70990C
treatment provided by	Plazi
scientific name	Hynobius guttatus
status	sp. nov.

Treatment

Hynobius guttatus sp. nov.

(Japanese name: Mahoroba-sanshou-uwo)

(English name: Mahoroba salamander)

( Figs. 7A, B View FIGURE 7 , 8A View FIGURE 8 , 9A, E, F View FIGURE 9 )

H. naevius View in CoL (part, Kinki local form): Sato 1943: 207.

H. naevius (part, samples 1–6, Chubu-Kinki subcluster in Group B): Tominaga et al. 2005a: 921–937.

H. naevius View in CoL (part, samples 1–7, Chubu and Kinki subgroup in Group B): Tominaga et al. 2005b: 1229–1244, Fig. 6A. H View in CoL View FIGURE 6 . naevius (part, samples 1–6, Chubu-Kinki samples in Clade 4): Tominaga et al. 2006: 677–684.

H. yatsui View in CoL (part): Tominaga et Matsui 2008: 107.

H. stejnegeri View in CoL (part): Matsui et al. 2017: 538.

Holotype: T2804 ( Fig. 7A, B View FIGURE 7 ), an adult male from Yasugawa-dam, Koka-shi (formerly Tsuchiyama-cho), Shiga Prefecture (34 o 58’N, 136 o 21’E, alt. 420 m a.s.l.), collected by K. Nishikawa and S. Tanabe on 22 April 1996. GoogleMaps

Paratypes: All from the type locality: T2194, one male collected by S. Tanabe on 15 August , 1991; T2663- T2664, one female and one juvenile collected by S. Tanabe on 3 April 1994; T2799, one male collected by Y. Yasukawa on 9 April 1996; T2805–T2807, one female and two juveniles collected by S. Tanabe on 22 April, 1996; KUHE 28477–28483 View Materials , one male and six juveniles collected by A. Tominaga, and T. Sugihara on 20 March , 2001.

Referred specimens: KUHE 32250–32261 View Materials , 33456–33459 View Materials , 33461–33468 View Materials from Gero-shi , Gifu Prefecture ; KUHE 27396–27399 View Materials , 27406–27411 View Materials , 27531–27533 View Materials , 27571 View Materials , 27632 View Materials , 27636–27640 View Materials , 27838 View Materials , 28762–28766 View Materials , 28770– 28771 View Materials , 28774–28776 View Materials , 28781 View Materials , T3044–T3046, from Fujihashi-mura , Gifu Prefecture ; KUHE 28477–28483 View Materials , T2137, T2194, T2663–T2664. T2799, T2804–T2807, from Koka-shi (formerly Tsuchiyama-cho ), Shiga Prefecture ; KUHE 33451–34564 View Materials , from Kawachinagano-shi , Osaka Prefecture ; T1977, from Chihaya-Akasaka-mura, Osaka Prefecture; T2695, T2852–T2854, T2986–T2990, from Izumi-shi , Osaka Prefecture ; KUHE 22793 View Materials , 26096–26097 View Materials , from Shirahama-cho , Wakayama Prefecture ; KUHE 28671 View Materials , 29670–29672 View Materials , from Kozagawa-cho , Wakayama Prefecture ; KUHE 22790–22791 View Materials , 28961–28962 View Materials , 29253 View Materials , T3107–T3108, T3112–T3114, from Kudoyama-cho , Wakayama Prefecture .

Etymology: The specific name “ guttatus ” is derived from the Latin adjective signifying speckled and refers to the small brownish-white markings on brown ground color typical for this species.

Diagnosis: A small-sized species (adult SVL 51–67 mm in males and 51–66 mm in females) within the lotic breeding Hynobius , breeding in underground water in montane streams; dorsum with small brownish white spots; limbs and tail long; tips of fore- and hindlimbs adpressed on body not meeting (overlap of -2.0 to -1.0 costal folds in males and -2.5 to - 2 in females); fifth toe ill-developed; ova large, pigmentless; egg sacs short and string-like, without distinct whiptail structure on free end; most similar to H. stejnegeri , but with smaller body size, small number of upper and lower jaw teeth, and vomerine teeth, relatively larger head, and shallower vomerine teeth series ( Fig. 8A View FIGURE 8 ), and reddish brown to dark blue ground color with brownish white small dorsal marking of the trunk.

Description of holotype (measurements in mm): Head-body small ( SVL 55.5); head oval and moderately depressed, distinctly longer (HL 13.0, 23.4% SVL) than wide (HW 10.0, 18.0%); 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 1.8, 3.2% SVL), shorter ( UEL 3.1, 5.6% SVL) than snout (SL 3.8, 6.9% 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 parotoid gland; vomerine teeth series slightly wider ( VTW 3.1, 5.7% SVL) than long ( VTL 2.7, 4.8% SVL), vomerine teeth deep V-shaped, series nearly touching at midline ( Fig. 8A View FIGURE 8 ), tongue broad, both sides free from mouth floor; fore- and hindlimbs short and thick (FLL 12.7, 22.9% SVL; HLL 16.2, 29.2% SVL); number of costal grooves between axilla and groin 13; depressed limbs separated by two costal folds; relative length of fingers IV<I<III<II, toes V<I<II<IV<III; fifth toe poorly developed (5TL 0.3, 0.5% SVL); cloaca longitudinal slit; genital tubercle on anterior cloaca absent; tail short ( TAL 34.0, 61.2% SVL), cylindrical at base and middle ( BTAW 6.0, 10.8% SVL; BTAH 5.2, 9.4% SVL, MTAW 4.5, 8.1% SVL; MTAH 5.8, 10.4% SVL), slightly compressed posteriorly, caudal fin never developed; tip of tail slightly sharpened in lateral view.

Additional Measurements and counts of the holotype: IND (2.8, 5.1% SVL); IOD (3.2, 5.8% SVL); AGD (29.6, 53.3% SVL); TRL (42.5, 76.7% SVL); MXTAH (5.8,10.5% SVL); 2FL (2.1, 3.8% SVL); 3FL (2.0, 3.6% SVL); 3TL (3.6, 6.5% SVL); UJTN (62); LJTN (65); VTN (51).

Color: In life, brown in dorsal ground color, with small white markings, ( Fig. 7A View FIGURE 7 ). Underside of body lighter than dorsum covered with white marking ( Fig. 7B View FIGURE 7 ). In preservative, dorsal and ventral ground color tending to fade.

Variation: Morphometric data are summarized in Tables 3 View TABLE 3 and 4 View TABLE 4 . Sexual size dimorphism in SVL was absent. Males tended to have wider RHW (median=18.0% SVL) than in females (17.6% SVL). Males had longer RFL (23.8% SVL) and RHL (29.4% SVL) than in females (22.6% SVL and 28.9% SVL, respectively). Separation of limbs was greater in females (median=2.0 folds) than in males (1.5 folds). Males had RTL (median=67.0% SVL) than in females (64.4% SVL). Third toe was usually longer than the fourth like holotype. Fifth toe was almost always present but often poorly developed. Combined series of vomerine teeth tended to be wider in males ( VTW / VTL, median=101.5%) than in females (96.8%). Dorsal color and was usually more reddish and marking size was smaller in northeastern populations (from Gero-shi and Ibigawa-cho, Gifu Prefecture; Koka-shi, Shiga Prefecture) than in southwestern populations (from Tsu-shi, Mie Prefecture; Izumi-shi, Osaka Prefecture; Kudoyama-cho and Kozagawa-cho, Wakayama Prefecture) ( Tominaga et al. 2005b). Individuals from Aichi Prefecture seem to be larger than those from other areas ( Yamagami et al. 2007).

Eggs and egg sacs: The egg sac morphology of H. guttatus sp. nov. is shown in Fig. 9A View FIGURE 9 . Egg sacs were stringlike in shape with thin envelope, and lacked a distinct whiptail structure on the free end. The egg sac ranged from 70–100 mm in length and 11–12mm in width ( Yamagami et al. 2007). The clutch size was small, ranging from 11–19 (mean ± SD =15.5 ± 3.3, n = 13) ( Yamagami et al. 2007) and 7–17 (13.3 ± 3.8, n = 4) (this study). The diameters of ova from seven females were 5.4 ( Yamagami et al. 2007), 5.4–5.9 (5.6 ± 0.13, n = 14) mm, 5.4–6.0 (5.7 ± 0.18, n = 9) mm, 4.4–5.0 (4.8 ± 0.16, n = 10) mm, 4.3–4.8 (4.6 ± 0.17, n = 7) mm, 4.8–5.1 (5.0± 0.11, n = 10) mm, and 4.3–4.9 (4.6± 0.2, n = 10) mm, respectively. Both the animal and the vegetal poles were cream in color.

Larvae: Two fully grown larvae at St. 62 of Iwasawa & Yamashita (1991) of the first year in late July had SVL of 17.8 and 18.1 (mean = 18.0) mm and total length of 32.1 and 33.8 (mean = 33.0) mm; head rounded in dorsal and lateral views ( Fig. 9E, F View FIGURE 9 ); snout short and broadly rounded; eyes slightly protruded, inset from edge of head in dorsal view; labial fold indistinct; external gills developed; caudal fin higher than head; dorsal fin slightly higher than ventral fin; origin of dorsal fin at half of trunk; ventral fin originating from vent; tail tip weakly pointed; limbs short but slightly robust; claws on fingers and toes absent. In life, dorsum dark brown to black without marking; venter whitish and transparent; a few white dots scattered on the lateral side of the trunk, caudal fin transparent with small black dots.

Range: Known from mountain regions of Chubu-Kinki district, Western Japan, from Gifu and Aichi Prefectures to Wakayama Prefecture ( Fig. 10 View FIGURE 10 ). Hynobius guttatus sp. nov. is largely sympatrically distributed with H. kimurae in Chubu and Kinki districts and with H. boulengeri in Kinki district. The new species is also sympatrically distributed with Onychodactylus japonicus in some areas.

Morphological Comparisons: Hynobius guttatus sp. nov. is distinct from all 37 lentic breeding Hynobius species by having tail cylindrical at base and small number of large, unpigmented eggs per clutch. Hynobius guttatus sp. nov. is different from other Japanese lotic breeding congeners, including H. boulengeri , H. hirosei , H, shinichisatoi , H. ikioi , H. osumiensis , H. amakusaensis , H. kimurae , H. fossigenus , and H. katoi by the presence of white ventral marking on the trunk and smaller body size ( Nishikawa & Matsui 2014). Hynobius guttatus sp. nov. is similar to H. sematonotos in color, but differs in smaller body size and deeper vomerine teeth series. Hynobius guttatus sp. nov. is different from H. naevius and H. oyamai by coloration and smaller body size. Hynobius guttatus is distinguished from H. katoi , which is supposed to have similar breeding ecology, by the presence of dorsal marking on trunk and tail.

Hynobius guttatus sp. nov. is genetically close to H. tsurugiensis sp. nov. described below from eastern highland of Shikoku but is morphologically clearly distinguished from the latter by color and size of dorsal and ventral marking, smaller body size, relatively larger head, larger number of upper and lower jaw teeth, and vomerine teeth, and relatively deeper vomerine tooth series. Hynobius guttatus sp. nov. is also distinguishable from H. kuishiensis sp. nov., described below from Shikoku by larger number of upper and lower jaw teeth, and vomerine teeth, relatively larger head, and relatively deeper vomerine teeth series. Hynobius guttatus sp. nov. is similar in color to H. stejnegeri but is distinct from the latter by smaller body size, and relatively shallower vomerine teeth series.

Hynobius guttatus sp. nov. is slightly larger (SVL= 50.6–66.9 in males, 51.2–65.9 mm in females) than all Taiwanese species although their ranges overlapped (adult SVL usually 50–60 mm and less than 69 mm [ Lai & Lue 2008]). Also H. guttatus sp. nov. differs from all five Taiwanese species in larger RHL (22.1–25.5%SVL vs. mean RHL= 18.3–23.9% and), RHW (16.5–19.2% vs. mean RHW= 15.0–16.5%), RFLL (21.2–25.7% vs. mean RFLL= 19.1–25.0%), and RHLL (27.2–32.2% vs. mean RHLL= 22.4–28.9%): means calculated from data of Lai & Lue (2008). Hynobius guttatus sp. nov. also differs in coloration from Taiwanese species.

Natural history: Breeding occurs from April to June, when egg sacs are attached to stones under the ground around headwater of mountain streams. Larvae can metamorphose in early autumn without feeding like other lineages of Hynobius stejnegeri (sensu lato).