Schistura nebeshwari, Lokeshwor & Vishwanath, 2013

Lokeshwor, Y. & Vishwanath, W., 2013, Two new species of stone loaches of the genus Schistura from the Koladyne basin, Mizoram, India (Teleostei: Cobitoidei: Nemacheilidae), Zootaxa 3731 (4), pp. 561-576 : 563-568

Schistura nebeshwari , sp. nov.

( Fig. 1 )

Holotype. MUMF 11128 , 48.7 mm SL, male; India: Mizoram: Saiha District: from a stream at Phura village near Palak Lake (Koladyne basin); 22°15'32"N, 92°53'32"E, 161 m above sea level, Y. Lokeshwor et al., 8 April 2011.

Paratypes. MUMF 11125–11127 , 3 specimens, 47.2–54.6 mm SL, males; India: Mizoram: from Kolchaw River at Kolchaw (Koladyne basin); 22°23'89"N, 92°57'98"E, 146 m above sea level, Y. Lokeshwor et al., 1 April 2011 .— MUMF 11129 , 39.1 mm SL, males; data as for holotype .— MUMF 11130–11131 , 2 specimens, 31.2–34.6 mm SL, females; data as for holotype. One paratype ( MUMF 11126 , 47.2 mm SL) was dissected for study of the intestinal coil and air bladder .

Diagnosis. Schistura nebeshwari is distinguished from all other species of Schistura with a dorsal adipose crest on the caudal peduncle by the combination of the following characters: 11–14 dark olivaceous bars on the body, entire ventral surface of head with numerous small melanophores, an incomplete lateral line, three black spots at the dorsal-fin base, a complete prominent black basicaudal bar, lower jaw with a shallow median notch, no suborbital flap in males, an inflated cheek and deep caudal peduncle with prominent dorsal adipose crest.

Description. General appearance as in Fig. 1 . Morphometric data are in Table 1 and meristic characters in Table 2. Body relatively small, moderately elongate, slightly depressed anterior to dorsal-fin origin, compressed posteriorly. Dorsal profile of body slightly elevated from tip of snout at dorsal-fin origin, then straight up to end of dorsal-fin base, elevated towards middle of caudal peduncle, forming a prominent adipose crest. Head depressed, short, triangular in dorsal aspect. Snout slightly pointed in lateral aspect, long, its length about half dorsal head length. Interorbital distance narrow, about half length of snout.

Dorsal fin with 3 simple and 8½ (6)–9½ (1) branched rays, its origin in advance of pelvic-fin origin, midway on standard length. Anterior distal margin of dorsal fin convex, posterior distal margin straight. Second branched dorsal-fin ray longer than remaining branched rays. Anal fin with 3 simple and 5½ branched rays, almost reaching caudal-fin base, separated from it by about one eye diameter. Pectoral fin sub-acuminate, with 1 simple and 9 (3)– 10 (4) branched rays, reaching midway to pelvic-fin origin. Pelvic fin sub-acuminate, with 1 simple and 6 (2)–7(5) branched rays, its origin on vertical through base of dorsal-fin branched rays 2 or 3, not touching anus when adpressed, separated from it by a distance about twice eye diameter. Axillary pelvic-fin lobe well developed. Caudal fin with 9+8 branched rays, deeply emarginate, lobes subequal, lower lobe a little longer than upper one. Caudal peduncle 0.7–1.0 times longer than deep, with a prominent dorsal adipose crest along its entire length, a low ventral adipose crest on its posterior half. Largest known size 54.6 mm SL (MUMF 11125).

Body completely covered with deeply embedded minute cycloid scales except on chest and belly in front of anal-fin origin. Lateral line incomplete, with 49–66 pores, reaching vertical through anus or middle of anal-fin base. Cephalic lateralis system with 8 (1)–9 (6) supraorbital, 4+8 (1)–9 (6) infraorbital, 9 (3)–10 (4) preorperculomandibular and 3 supratemporal pores. Unculi blunt, low near margin of outer face of both jaws but slightly elevated on inner face, arranged side by side ( Fig. 2 ). Taste buds low bumps, arranged sparsely on lips and barbels.

Anterior nostril pierced anteriorly, a low leaf-like pointed tube. Mouth arched, 1.7–2.0 times wider than long. Lips fleshy, finely pleated. Lower lip with a deep broad median interruption with 2–3 furrows on interior edge on each side ( Fig. 3 ). Upper lip with a narrow lateral and broad median potion, no median incision, with very low regular furrows on entire lip (furrows deeper near corners of mouth). Processus dentiformis prominent, broad. Lower jaw with shallow median notch.

Barbels in three pairs, inner rostral barbel reaching corner of mouth; outer one reaching vertical through anterior margin of eye. Maxillary barbel reaching vertical through posterior margin of eye. Free posterior chamber of air bladder small, spherical, concealed beneath manubrium ( Fig. 4a ). Intestine with small a loop, a short distance from stomach ( Fig. 4b ).

Sexual dimorphism. Males with slender body anterior to dorsal fin, slightly inflated cheek, deeper caudal peduncle with a prominent dorsal adipose crest, no suborbital flaps. Females with a low dorsal adipose crest, slightly deeper body at dorsal-fin origin.

Coloration. In fresh specimens: body with 11–14 broad dark olivaceous bars on dull white background. Four or five black saddles on dorsum in pre-dorsal region, 3 in sub-dorsal and 4–6 in post-dorsal, each saddle continued on flank, forming broad bars. All bars on caudal peduncle meeting their antimere ventrally. Some of bars, especially at vertical through pre-anal region, split ventrally below mid-lateral line. Interspaces as wide as half of each bar. Head light olivaceous dark on dorsum, dull white laterally and ventrally; entire ventral surface of head with numerous melanophores. Three black spots at dorsal-fin base, first at bases of simple and first branched dorsal-fin rays, second at bases of branched rays 3–5, third at bases of branched rays 7–9. All fins golden yellow. Basicaudal bar black, broad, completed with an elongated backwardly-directed portion at dorsal extremity.

In 10% formalin: all bars dark brown on light yellowish cream background. Fins dull white. Ventral portion of belly and ventral and ventro-lateral portion of head light yellowish cream.

Distribution. Known only from both the Kolchaw River and a stream near Phura village near Palak Lake (the Koladyne basin), Saiha District, Mizoram, India ( Fig. 5 ).

Habitat. In southern Mizoram, this species is a typical inhabitant of brooks and streams with slow to swift current, among small pebbles, stones and boulders. The holotype was collected from a stream near Phura village near Palak Lake (the Koladyne basin), among small pebbles, in slow current. Three paratypes were also collected from the Kolchaw River near Kolchaw, Saiha District, Mizoram, India ( Fig. 6 ). Other species occurring with Schistura nebeshwari were Bagridae : Olyra sp. ; Cyprinidae : Barilius profundus Dishma & Vishwanath, 2012 , Devario sp. , Pethia sp. , Garra sp. ; Nemacheilidae : Schistura scyphovecteta ; and Sisoridae : Glyptothorax jayarami Rameshori & Vishwanath, 2012 .

Etymology. The species is named after Kongrailakpam Nebeshwar Sharma in recognition of his assistance to the authors during the field work in Mizoram. It is a noun in the genitive case.

Schistura nebeshwari Schistura scyphovecteta

(7 specimens) (5 specimens)

Dorsal-fin rays iii/8½–9½ (8½) iv/7½

Anal-fin rays iii/5½ iii/5½

Branched caudal-fin rays 9+8 9+8

Pectoral-fin rays i/9–10 (9) i/10

Pelvic-fin rays i/6–7 (7) i/7

Lateral-line pores 49–66 (66) 78–84 (84)

Pores in Cephalic lateralis system

Infra-orbital pores 4+8–9 (4+9) 3+9

Supra-orbital pores 8–9 (9) 9

Supra-temporal pores 3 3

Preoperculo-mandibular pores 8–9 (9) 9–10 (10)

Figures

FIGURE 1. Schistura nebeshwari, n. sp.: a. holotype, MUMF 11128, 48.7 mm SL, male (lateral view); b. holotype (dorsal view); c. holotype (ventral view); d. paratypes, MUMF 11130, 31.2 mm SL, female (lateral view).

FIGURE 2. Oromandibular structures of Schistura nebeshwari (MUMF 11126, 47.2 mm SL). A. Ventral surface of head. B. Close up box i in A, showing taste buds on lower lip and upper lip, and rostral barbel. C. Close up box ii in B, showing unculi on upper jaw. LJ ─ lower jaw; LL─lower lip; UJ ─ upper jaw; UL ─ upper lip.

FIGURE 3. Lip structure of Schistura nebeshwari (MUMF 11128, 48.7 mm SL). Scale bar 1 mm.

FIGURE 4. Schistura nebeshwari, n. sp. (MUMF 11126, 47.2 mm SL) showing a. free posterior chambers of air bladders; b. coiling patterns of intestine. pab — posterior chamber of air bladder. Scale bar 1 mm.

FIGURE 5. Map showing type locality of Schistura nebeshwari and Schistura scyphovecteta.

FIGURE 6. Mizoram: stream Kolchaw at Kolchaw, collection site of Schistura nebeshwari; looking upstreams and to the east. Photo: Y. Lokeshwor.