Schistura obliquofascia, Lokeshwor & Barat & Sati & Darshan & Vishwanath & Mahanta, 2012

Lokeshwor, Y., Barat, A., Sati, J., Darshan, A., Vishwanath, W. & Mahanta, P. C., 2012, Schistura obliquofascia, a new loach from Uttarakhand, India (Cypriniformes: Nemacheilidae), Zootaxa 3586, pp. 255-263 : 256-261

Schistura obliquofascia sp. nov.

( Fig. 1)

Holotype. MUMF 11058 , 73.3 mm SL, female; India: Uttarakhand State, Kalsa River at Chanfi, Ganga basin, 29°22'06" N, 79°34'44" E; A. Barat and Party, 25 March 2009.

Paratypes. MUMF 11055 , 11059 & 11061, 3, 80.0– 98.4 mm SL, males ; MUMF 11056 , 11057 & 11060, 3, 67.0– 67.5 mm SL, females; same data as holotype; two specimens ( MUMF 11060 & 11061) were dissected for confirmation of sexes, air bladder and intestinal coil ).

Diagnosis. Schistura obliquofascia can be distinguished from congeners in having a unique combination of the following characters: 12–14 obliquely arranged olivaceous dark bars on body; lateral line complete with 104–112 pores; dorsal fin with 3–4 simple and 8½ branched rays, marked with irregularly arranged black spots; caudal fin with 8+8 branched rays, slightly emarginated, lobes equal in length; dorsal adipose crest prominent; 10–11 pores in preorperculo-mandibular canal; no suborbital flap.

Description. Biometric data are given in Table 2. Body elongate, thick, stout, subcylindrical in cross section anteriorly and compressed posteriorly. Dorsal profile of body almost straight, but slightly elevated at dorsal-fin origin. Head depressed, short and triangular. Snout rounded and short.

Dorsal fin with 3–4 simple and 8½ branched rays, origin midway between tip of snout and caudal-fin base, slightly in advance of pelvic-fin origin. Anterior margin of dorsal fin convex, posterior margin slightly concave. Anal fin with three simple and 5½ branched rays, reaching near base of caudal fin, leaving a gap equal to eye diameter. Pectoral fin with 11 rays, oval in shape, reaching about one-third distance to pelvic-fin origin (38.3–39.9% prepelvic length). Pelvic fin with eight rays, origin under 1st branched dorsal-fin ray, not touching the vent when adpressed, leaving a gap equal to diameter of eye. Axillary pelvic-fin lobe well developed. Caudal fin with 8+8 branched rays, slightly emarginate, lobes of equal length. Caudal peduncle 1.0–1.3 times longer than deep, with high dorsal adipose crest on entire length and low ventral adipose crest on posterior half of peduncle. Largest recorded size 98.4 mm SL male (MUMF 11059).

Body entirely covered with embedded scales. Cephalic lateral-line system with 8 supraorbital, 4+8 infraorbital, 10–11 preorperculo-mandibular and 3 supratemporal pores. Unculi are present on lips and barbels. Lateral line complete, with 104–112 pores.

Holotype Paratypes

MUMF 11058 MUMF 11055–11061

range mean SD

Standard length 73.3 67.0–98.4

% SL

Body depth 16.8 13.0–17.2 15.7 1.4 Head depth at nape 12.3 11.3–12.4 12.0 0.4 Lateral head length 21.3 20.9–22.0 21.3 0.4 Dorsal head length 19.1 18.2–19.3 18.8 0.4 Head depth at eye 10.4 9.7–12.3 10.5 0.6 Caudal-peduncle length 12.8 10.7–14.2 12.9 1.1 Caudal-peduncle depth 10.9 10.0–12.0 11.1 0.7 Predorsal length 51.8 49.1–53.0 51.2 1.4 Prepelvic length 52.9 52.9–55.4 54.2 1.0 Preanus length 75.6 74.0–76.9 75.4 1.2 Preanal length 82.0 79.1–83.6 81.1 1.6 Dorsal-fin height 12.8 11.2–13.9 13.0 0.9 Pelvic-fin length 18.6 18.2–20.2 19.2 0.7 Anal-fin depth 15.4 15.4–16.7 16.3 0.4 Pectoral-fin length 20.5 20.5–22.1 21.3 0.6 Maximum head width at cheek 17.7 15.8–17.7 16.5 0.6 Head width at nares 12.6 11.4–12.6 12.0 0.5 Body width at anal-fin origin 7.4 4.3–7.4 6.2 1.0 Body width at dorsal-fin origin 14.5 9.9–14.5 12.3 1.7 % HL

Snout length 50.0 50.0–59.8 53.0 3.3 Interorbital distance 47.1 40.0–48.0 43.6 2.9 Eye diameter 17.1 14.2–18.2 16.2 1.3 Mouth gape width 42.9 39.8–50.0 45.1 3.1 Head depth at eye 54.3 50.2–58.1 55.4 2.7 Head depth at nape 64.3 60.8–68.2 64.2 2.6 Body depth at dorsal-fin origin 87.9 70.3–93.5 84.1 8.9 Depth of caudal peduncle 57.1 54.1–65.9 59.4 4.3 Length of caudal peduncle 67.1 58.5–73.8 66.4 5.7 Maximum head width 92.8 85.1–92.8 88.1 2.9 Body width at dorsal-fin origin 75.7 53.4–76.6 68.5 9.3 Body width at anal-fin origin 38.6 23.0–38.6 32.2 5.8

Anterior nostril pierced in front side of low flaplike pointed tube. Mouth arched, 1.8–2.1 times wider than long. Lips fleshy and finely pleated. Lower lip with deep median interruption without forming lateral triangular pads ( Fig. 2). Inner margin of lower lip slightly thicker than lateral. Upper lip with small median incision. Processus dentiformis prominent, with median notch. Lower jaw with shallow median notch. Free posterior chamber of air bladder absent. Intestine with large loop which reaches forward and touches posterior great curvature of stomach (Fig. 3).

Barbels moderately long; inner rostral barbel much shorter, and short distance from posterior margin of corner of lip; outer one much longer, reaching to vertical of anterior rim of orbit. Maxillary barbel reaches nearly to vertical from posterior rim of orbit.

Sexual dimorphism. Females are smaller and body bars are well separated; width of bars almost equal to interspaces. In males, dorsal surface of body is much darker than in females, bars coalesce on back; predorsal bars are fewer and broader; pectoral fin slightly longer than in females.

Color. In 10% formalin: Body with 12–14 quite regularly arranged olivaceous dark bars, fading ventrolaterally, obliquely placed on creamy-white background. Four–5 bars in predorsal region, 2–3 under dorsal fin, and 6–7 between base of last dorsal-fin ray and caudal-fin base. Bars in front of anal fin, generally extend downward to horizontal level of pectoral fin while those on caudal peduncle meet on midventral line. Head dark olive above, becoming lighter ventrolaterally and much lighter on venter. Ventral side of body creamy white. Dorsal fin with irregularly arranged black spots. Base of simple and first branched rays marked with dark spot. Anterior first to fifth pectoral-fin rays tinged with dusky coloration. Pelvic and anal fins marked with irregularly arranged dusky spots. Prominent, complete vertical black bar present at base of caudal fin. Caudal fin with irregularly arranged dark spots, sometimes arranged in three rows.

Distribution. Presently known from Kalsa River at Chanfi, a tributary of the Gola River, Ganga basin, Uttarakhand, India ( Fig. 4).

Etymology. The specific epithet is derived from oblique: prefix meaning slanting or inclining in direction, and fascia (Latin), meaning band, referring to the obliquely arranged bars on the body.

Discussion

The genus Schistura includes a large number of species distributed over a vast geographical area. As a rheophilic species is restricted to a particular region and not likely to occur outside of it ( Ng & Rachmatika 2005), the new species has been compared with those occurring in the Ganga-Brahmaputra basin. All of the species of the basin except S. papulifera have dark bars on the body. Besides the presence of the bars, S. obliquofascia can be distinguished from S. papulifera in absence (vs. presence) of skin projection on the lower half of the head and in having three (vs. five) pores in the supratemporal canal of the cephalic lateral-line system, 8+8 (vs. 9+8) branched rays in the caudal fin, and 11 (vs. 12–13) rays in the pectoral fin. The new species can be easily differentiated from the other 11 congeners in having oblique (vs. vertical) bars on the body and 16 (vs. 17–18) branched rays in the caudal fin.

Schistura obliquofascia is further distinguished from S. beavani in presence (vs. absence) of nasal barbel, and lower body depth (14.3% standard length vs. 20); from S. chindwinica in having 8+8 branched caudal rays (vs. 9+8), prominent adipose crest (vs. absence), longer snout (50.0–59.8% HL vs. 39.0–45.0) and wider interorbital distance (40.0–48.0% HL vs. 30.0–37.0). It also differs from S. fasciata in having fewer branched caudal-fin rays (8+8 vs. 9+8), longer pelvic-fin rays (18.2–29.2% SL vs. 13.6–17.7), and wider interorbital distance (40.0–48.0% HL vs. 25.1–34.8).

Day (1878) described Schistura multifasciata from Darjeeling and Assam. The holotype of this species at ZSI is in a poor state of preservation and is not suitable for comparison. Thus the data of Day (1878) and Menon (1987) were used for comparison. The new species differs from S. multifasciata in having 3–4 (vs. 2) simple dorsal-fin rays, 8½ (vs. 7½) branched dorsal-fin rays, 8 (vs. 9) pelvic-fin rays and 12–14 (vs. 18–30) bars on body. The new species also differs from S. minutus in having strongly developed (vs. weakly formed) processus dentiformes, 8 (vs. 7) pelvic-fin rays and larger (vs. smaller) size at maturity, i.e., SL = 67.0– 98.5 mm vs. 26.2–38.9. It can also be distinguished easily from S. reticulofasciata in the presence of complete (vs. incomplete) lateral line, longer snout (50.0–59.8% HL vs. 45.9) and narrower eye (diameter 14.2–18.2% HL vs. 27.4).

Schistura obliquofascia is further distinguished from S. savona in having more dorsal-fin rays (3–4/8½ vs. 2/ 7½), pectoral-fin rays (11 vs. 10), and 12–14 broad olivaceous dark bars (vs. 9–10 narrow yellowish bars). A specimen labeled as S. reticulofasciata in ZSI, Shillong (ZSI VF/ERS 2629) has been examined in detail and identified as S. sijuensis as it has a complete lateral line with 93 pores, an important diagnostic feature of the species. The new species is distinguished from S. sijuensis in having shorter head (18.2–19.3% SL vs. 21.4–25.8), longer snout (50.0–59.8% HL vs. 32.4–44.4), and no suborbital flap (vs. presence). It is further distinguished from S. tigrinum in having more (8 vs. 7) pelvic-fin rays; complete (vs. incomplete) lateral line, wider interorbital distance (40.0–48.0% HL vs. 27.1–30.3) and wider head at check (85.1–92.8% HL vs. 74.6–81.8).

The new species can be easily differentiated from S. tirapensis in having complete lateral line (vs. incomplete), shorter head (18.2–19.3% SL vs. 25.5–28.6), and longer snout (50.0–59.8% HL vs. 43.5–46.2). It also differs from S. zonata in having spotted (vs. nonspotted) dorsal and caudal fins; 12–14 (vs. 11) bars on side of body and blunt (vs. pointed) snout.

Shrestha (2008) reported Schistura himachalensis (Menon) , S. horai (Menon) , S. rupecula McClelland , and S. sikmaiensis (Hora) from the Ganga basin, but all might be due to misidentifications. Schistura himachalensis , S. horai and S. rupecula were originally described from the Indus basin, while S. sikmaiensis was described from the Chindwin basin. Schistura obliquofascia , however, is distinguished from S. rupecula in having 11 (vs. 10) pectoral-fin rays and 16 (vs. 18) caudal-fin branched rays; from S. himachalensis in having 12–14 (vs. 8–11) bars on side of body, 8½ (vs. 7) branched dorsal-fin rays, 11 (vs. 10) pectoral-fin rays, 8 (vs. 7) pelvic-fin rays, caudal fin emarginate (vs. deeply forked) with 16 (vs. 18) branched rays, lateral line complete (vs. incomplete), and spotted (vs. unspotted) fins; and from S. horai in having 3 (vs. 2) simple anal-fin rays, narrower eye diameter (14.2–18.2% HL vs. 40.3), and wider interorbital distance (40.0–48.0% HL vs. 34.8). The new species is also distinguished S. prashadi and S. sikmaiensis , respectively, in having fewer branched caudal-fin rays (8+8 vs. 9+8) and shallower head depth at nape (11.3-12.4% SL vs. 13.0–14.5).

Genetic variation. A total of 5 sequences of cyt b (307 bp) gene of Schistura obliquofascia were successfully amplified and analyzed to determine genetic variation within the species. The average frequency of four nucleotides was A = 26.3%, T = 30.4%, C = 27.6% and G = 15.8% in all five sequences. Nucleotide sequences of cyt b were A+T rich (56.8%) with an anti-G bias (15.8%). Cyt b gene revealed 10 variable sites of which two were parsimony informative and 8 were singleton variable sites.

Although only three species of Schistura from Ganga-Brahmaputra Basin were included in this analysis, the Neighbor-joining (NJ) tree ( Fig. 5) of cyt b gene sequences consisted of two divergent clusters. Bootstrap values higher than 66% are indicated. Schistura obliquofascia was closer with S. beavani in a single cluster, while S. corica was clustered in another group. Mean genetic distance (P distance) over all species was 0.175. Mean genetic distance between species ranged from 0.179 to 0.320 ( Table 3). The lowest genetic distance was between S. obliquofascia and S. beavani (0.179). Neighbor-joining tree and genetic distance data show S. corica to be genetically distant from the S. obliquofascia and S. beavani .