Schistura kottelati, Tuan & Thao & Quang, 2018

Tuan, Ho Anh, Thao, Hoang Ngoc & Quang, Ngo Xuan, 2018, Schistura kottelati, a new species of loach from the Phong Nha-K ẻ Bàng National Park in central Vietnam (Teleostei: Nemacheilidae), Raffles Bulletin of Zoology 66, pp. 142-148 : 142-147

Schistura kottelati , new species

( Figs. 1–5 , Table 1)

Holotype. BMVU 1101 , 37.0 mm SL; Vietnam: Quang Binh province: Bo Trach district: Xuan Trach commune: a pool in Hung Dang valley of Phong Nha-Kẻ Bàng National Park ; 17°37′12″N, 106°04′01″E, 83 m asl, Ho Anh Tuan & Hoang Ngoc Thao, 24 August 2011.

Paratypes. BMVU 1102–1128 , 27 , 26.7–42.1 mm SL ; ZRC 54928 (formerly BMVU 1130–1138 ), 9, 28.5–33.6 mm SL; same data as holotype .

Diagnosis. Schistura kottelati differs from the other species of genus Schistura known from Vietnam and adjacent areas in Laos by the unique combination of the following characters: lateral line very short, with 5–14 pores; pelvic fin with 1 unbranched and 8 branched rays; a long maxillary barbel (reaching vertical through nape) and inner rostral barbel (reaching vertical through anterior margin of eye); body without obvious markings; caudal fin deeply forked (length of median ray 1.5–1.7 times in length of upper slobe); no external sexual dimorphism; caudal peduncle slender (its length 8.0–11.6% SL); a large eye (eye diameter 4.7–6.2% SL); and wide interorbital region (interorbital width 9.1–11.7% SL).

Description. See Figs. 1–5 for general appearance and Table 1 for morphometric data of holotype and 27 paratypes. A small-sized, moderately elongated loach. Body anteriorly slightly compressed, caudal peduncle compressed. Maximum body depth between pectoral-fin base and dorsal-fin origin. Head depressed, depth at nape 0.8–1.0 (mean 0.9) times in its width. Snout round in lateral view, slightly squarish in dorsal view. Width of head increasing from level of mouth backwards to anterior part of opercle, from that point onwards body regularly narrowing until caudal-fin origin. Caudal fin deeply forked. Low ventral and dorsal adipose crests on caudal peduncle; caudal peduncle 1.2–1.7 (mean 1.4) times longer than deep. Distal margin of dorsal fin convex. Largest known individual 42.1 mm SL.

Dorsal fin with 3 simple and 7½ branched rays; distal margin of dorsal fin straight or very slightly convex. Anus slightly in front of anal-fin origin. Anal fin with 3 simple and 5½ branched rays, reaching about halfway to caudal fin base. Caudal fin with 9+8 branched rays (9+ 9 in one paratype), lobes rounded or slightly pointed. Pelvic fin with 1 unbranched and 8 branched rays; origin under last unbranched or first branched dorsal-fin ray; reaching distinctly beyond half of distance to anal-fin origin; usually just reaching anus. Pectoral fin with 1 unbranched and 9 branched rays, reaching half of distance between bases of pectoral and pelvic fins.

Posterior part of body covered by embedded scales. Scales only sparsely-set at predorsal flank, deeply embedded. Lateral line incomplete, with 5–14 pores (mean 10), reaching maximally to pelvic-fin base. Cephalic lateral line system with 6 supraorbital, 6+8 infraorbital, 8–10 preoperculomandibular and 3 supratemporal pores.

Anterior nostril pierced in front side of a flap like tube, with a low anterior rim. Eye 3.5–4.8 times in head length, directed dorsolaterally, diameter 1.5–2.2 (mean 1.8) times in interorbital width. Interorbital distance increasing with body size, while relative size of eye slightly decreasing. Processus dentiformis wide, low, broadly rounded. Mouth gape about 1.6–1.9 times wider than long ( Fig. 5a ). Lips thin; upper lip with a well-marked median incision and no furrows. Lower lip with a narrow median interruption, no furrows, but few small folds towards corners of mouth. Inner rostral barbel reaching vertical of anterior margin of eye; outer one reaching vertical of posterior margin of eye. Maxillary barbel reaching vertical of nape.

Colouration. In freshly preserved specimens, body sides brownish, darker colour on dorsal side and lighter on belly; becoming white after a few days in formalin. Dorsal midline covered by thick yellow stripe from posterior of head, via dorsal-fin base, to caudal-fin base. Head a faint purplish colour laterally without any obvious pigmentation or patterns. Caudal base with a thin and faint dark bar, thicker at upper and lower extremities, very weak in middle area and not reaching dorsal and ventral midlines. Fins hyaline, without pigments on rays and membranes.

Overall colouration of juveniles as adult individuals but having a series of 3–7 dark blotches on flanks, varying in shape. In some juveniles, a chain of tiny black dots along lateral line and dorsal midline ( Fig. 3 ).

Sexual dimorphism. None observed.

Distribution and habitat. Schistura kottelati is presently known only from a single pool ( Fig. 6 ) in a large karstic area of the Hung Dang valley, Quang Binh province ( Fig. 7 ). Hung Dang valley is located in the core area of the Phong Nha-Kẻ Bàng National Park. The pool where the species was found is about 2 × 3 meters large and 0.7 meters at its deepest point. Although located in the Gianh River drainage, the pool is about 83 m asl and completely isolated from any adjacent water bodies. Water is available by rain and underground water. This pool is isolated and the nearest water body is 5 km away. It is a very important site protected by the National Park management because it is also a source of water for the local community. No other fish species were observed in the pool. We do not expect the species to be endemic to this very small pool, but suspect, that the major population lives underground.

Etymology. The species is named for Maurice Kottelat, in appreciation for his research on Eurasian freshwater fishes, among others those of Vietnam. A noun in genitive.

Remarks. Schistura kottelati is known only a single locality in Central Vietnam. In the latest and most comprehensive survey of the nemacheilid fauna of Central Vietnam, Freyhof & Serov (2001) reported 19 species of Schistura from Central Vietnam ( S. antennata , S. bachmaensis , S. carbonaria , S. dalatensis , S. finis , S. hingi , S. huongensis , S. implicata , S. konphengi , S. kontumensis , S. namboensis , S. nasifilis , S. pervagata , S. psittacula , S. sokolovi , S. spiloptera , S. susannae , S. thanho , and S. yersini ). Schistura kottelati differs from all these species by not having any distinct dark pigmentation pattern on the body, while the other species have vertical bars on the body sides (sometimes weak, but present at least in the form of dorsal saddles or large midlateral blotches) and a distinct black bar at the base of caudal fin. It has a shorter lateral line than any other Central Vietnamese species (5–14 pores vs. at least 38).

According to Kottelat (2001a), in northern Vietnam another six species of Schistura are known or expected to occur: Schistura callichromus , S. caudofurca , S. chapaensis , S. fasciolata , S. incerta , and S. orthocauda . Schistura kottelati differs from all these species by lacking a colour pattern (vs. having head and body covered with large black blotches in S. callichromus or having distinct dark bars on the body in the other species) and having a very long rostral barbel (inner rostral barbel reaching vertical through anterior margin of eye vs. not reaching vertical through anterior margin of eye). Additional species of Schistura that have been described from northern Vietnam since the publication by Kottelat (2001a, 2012) are: S. athos , S. hoai , S. mobbsi , S. phongtoensis , S. pumatensis , S. sonlaensis , S. spekuli , S. tamduongensis , and S. trilineata . Schistura kottelati differs from all these species except S. mobbsi and S. spekuli by lacking a colour pattern or pigmentation in adults (vs. having a middorsal and a midlateral stripe in S. sonlaensis and S. trilineata or bars on the body in the other species) and by having longer barbels (inner rostral barbel reaching vertical through anterior margin of eye vs. not reaching vertical through anterior margin of eye). Schistura kottelati differs from S. mobbsi and S. spekuli by the presence of eyes (vs. absence) and 9 rays in the pelvic fin (vs. 7 in S. mobbsi , 8 in S. spekuli ).

The area in Laos adjacent to the Gianh River drainage is drained by the Xe Bangfai, a left tributary of the Mekong that has been studied by Kottelat (1998, 2000, 2001b). The following species of Schistura have been recorded in this drainage: S. daubentoni , S. isostigma , S. nicholsi , and S. punctifasciata . In the middle of its course, the Xe Bangfai flows for several km underground in a natural tunnel. Upstream of the tunnel, the Xe Bangfai flows parallel and close to the Lao-Vietnam border. Until now, a single species of Schistura ( S. nicholsi ) has been collected upstream of the tunnel ( Kottelat, 1998, 2016, and pers. comm.) but this area is still very poorly known and difficult to access. Schistura kottelati differs from S. nicholsi by the absence (vs. presence) of dark bars on the body sides, by having longer barbels (maxillary barbel reaching, vs. not reaching, vertical through nape), a shorter lateral line (lateral line with 8–14 pores, not reaching vertical through pelvic-fin origin vs. complete) and a deeply forked caudal fin (length of median ray 1.5–1.7 times in length of upper lobe vs. 1.1–1.3).

Comparative material. Schistura antennata: IAPG A 3392– 3400, 9, 25.9–48.7 mm SL; Vietnam: Ha Tinh prov.: stream at Son Kim ; 18°24.25″ N 105°11.10 ″E.

Schistura athos: RIA 1 uncatalogised, 2, 95.2–101.7 mm SL; Vietnam: Dien Bien prov.: Creek Nâm Ngam.

Schistura bachmaensis: IAPG A 10952–10596, 5, 35.8–42.7 mm SL; Vietnam: Thua Thien Hue prov. : stream Suoi Voi; 16°14.58″ N 107°59.39 ″E.

Schistura carbonaria: IAPG A 3362–3366, 5, 44.5–53.9 mm SL; Vietnam: Thua Thien Hue prov. : stream Khe Vinh An; 16°11.58″ N 107°43.76 ″E.

Schistura caudofurca: RIA 1 uncatalogued, 2, 76.6–82.7 mm SL; Vietnam: Ha giang prov.: Lo River.

Schistura dalatensis: IAPG A 3244–3255, 12, 31.8–47.6 mm SL; Vietnam: Lam Dong prov.: stream Dai Tan ; 16°46.64″ N 108°19.28 ″E.

Schistura hingi: IAPG A 3418–3429, 12, 33.1–44.2 mm SL; Vietnam: Ha Tinh prov.: small tributary of river Lam ; 18°26.24″ N 105°14.36 ″E.

Schistura huongensis: IAPG A 3355–3361, 7, 34.9–43.1 mm SL; Vietnam: Thua Thien Hue prov. : stream Khe Vinh An; 16°11.58″ N 107°43.76 ″E.

Schistura implicata: CMK 25835, 3, 50.0– 62.8 mm SL; Laos: Houapan prov. : River Nam Xam; 20°19.25″ N 104°31.36 ″E.

Schistura konphengi: IAPG A 3280–3285, 6, 37.5–45.3 mm SL; Vietnam: Thua Thien Hue prov. : stream running to Sesap; 16°12.31″ N 107°17.41 ″E.

Schistura kontumensis: IAPG A 3457–3459, 3, 40.0– 56.3 mm SL; Vietnam: Kontum prov.: stream Pako ; 14°23.23″ N 107°54.15 ″E.

Schistura namboensis: ZFMK 24095–24104, 10 paratypes, 45.8–54.8 mm SL; Vietnam: Dac Lac prov.: small stream at Ea Nuol. — IAPG A3266–3279 , 14 , 20.5–35.5 mm SL ; Vietnam: Gia Lei prov.: stream Azun ; 12°41.58″ N 107°57.74 ″E .

Schistura nicholsi: CMK 24709, 3, 39.4–51.1 mm SL; Laos: Bolikhamsai prov.: river Nam Xao . — IAPG A9602 , 1 , 40.1 mm SL; Thailand: Phetchabun prov.: Mun River ; 14°48′27″ N 106°55′52″ E.

Schistura pervagata: CMK 25708, 3, 47.7–53.6 mm SL; Laos: Houapan prov. : River Ma. — CMK257751, 3, 30.7–60.8 mm SL; Laos: Houapan prov.: River Ma; 20°31′09″ N 104°21ʹ44 ʺE.

Schistura phongthoensis: RIA 1 uncatalogued, 5, 55.5–68.6 mm SL; Vietnam: Lai Chau prov.: Nam So River (type locality).

RAFFLES BULLETIN OF ZOOLOGY 2018

Schistura psittacula: IAPG A 3200v3205, 6, 27.0– 46.9mm SL; Vietnam: Quang Tri prov.: stream Cam Lo ; 16°47.00″ N 106°53.86 ″E.

Schistura sokolovi: IAPG A 3384–3385, 2, 49.1–50.3 mm SL; Vietnam: Gia Lei prov. : stream Azun; 14°02.34″ N 108°21.07 ″E.

Schistura spiloptera: IAPG A 3401–3417, 17, 23.7–44.4 mm SL; Vietnam: Thua Thien-Hue: unnamed mountain stream; 16°10.59″ N 108°08.42 ″E.

Schistura susannae: IAPG A 3223–3232, 10, 34.2–49.2 mm SL; Vietnam: Quang Nam Danang prov.: stream Mong Mo ; 16°09.67″ N 108°07.73 ″E.

Schistura thanho: IAPG A 3310–3319, 10, 25.5–36.4 mm SL; Vietnam: Binh Dinh prov.: stream Vinh Thanh ; 14°16.19″ N 108°45.69 ″E.

Schistura yersini: IAPG A 3325–3336, 12, 25.5–36.4 mm SL; Vietnam: Lam Dong prov.: stream Dai Tan; 11°46.64″N, 108°19.28″E.

Further data obtained from Endruweit (2013), Freyhof & Serov (2001), Kottelat (1998, 2000, 2001a, b, 2016), Nguyen et al. (2010), and Zhu (1989).

Figures

Fig. 1. Schistura kottelati BMVU 1101, holotype, 37.0 mm SL; Vietnam: Phong Nha-Kẻ Bàng National Park.

Fig. 2. Schistura kottelati, BMVU 1104, paratype 36.5 mm SL; Vietnam: Phong Nha-Kẻ Bàng National Park.

Fig. 3. Schistura kottelati, BMVU 1107, paratype 33.8 mm SL; Vietnam: Phong Nha-Kẻ Bàng National Park.

Fig. 4. Schistura kottelati, BMVU 1107, paratype 33.8 mm SL; Vietnam: Phong Nha-Kẻ Bàng National Park.

Fig. 5. Head of Schistura kottelati. C BMVU 1112, 31.0 mm SL, ventral view; B, BMVU 1125, 30.6 mm SL, lateral view.

Fig. 6. Type locality of Schistura kottelati; Vietnam:Phong Nha-Kẻ Bàng National Park, pond in Hung Dang valley, 24 August 2011.

Fig. 7. Type locality of Schistura kottelati (black circle) in Phong Nha-Kẻ Bàng National Park, central Vietnam.