Schistura paucireticulata, Vishwanath, W. & Kosygin, L., 2013

Vishwanath, W. & Kosygin, L., 2013, Schistura paucireticulata, a new loach from Tuirial River, Mizoram, India (Teleostei: Nemacheilidae), Zootaxa 3683 (5), pp. 581-588 : 582-585

Schistura paucireticulata , new species

( Fig. 1 )

Holotype. MUMF 11120, 61.4 mm SL, male; India: Mizoram: Aizawl District: Tuirial River near Aizawl (the Barak-Surma-Meghna river system); 23º43ʹ12.49ʺN, 92º47ʹ59.43ʺE, altitude 175 m above sea level; K. Nebeshwar et al., 2004.

Paratopotypes. MUMF 11121, 59.7 mm SL, male; MUMF 11122-11123, 2 specimens, 55.6–57.1 mm SL, females; same data as holotype.

Diagnosis. Schistura paucireticulata , new species, appears to be most similar to congeners outside the Ganga- Brahmaputra and Barak-Surma-Meghna river basins, viz., S. bella , S. conirostris , S. longa , S. mahnerti , S. poculi , and S. vinciguerrae , in having complete lateral line and similar arrangement of dark saddles and bars on side of body; however, it is distinguished from them in having 8–9 brown bars and saddles on body (vs. variable colour pattern consisting of bars, blotches and saddles in S. bella ; 3 saddles in predorsal region and 17 bars in S. mahnerti ; 11–12 blotches on dorsum and 15–17 bars in S. poculi ; 10–14 bars in S. conirostris ; 10–16 bars in S. vinciguerrae and S. longa ). Furthermore, it is distinguished from congeners in having saddles in front of dorsal fin dividing into 2-3 small bars forming reticulated appearance as they descend onto side of body; basicaudal bar black, dissociated; dorsal fin spotted, with 4 simple and 8½ branched rays; 3 simple and 6 branched anal-fin rays; lateral line complete; caudal fin deeply emarginated with 9+8 branched rays; well developed axillary pelvic lobe; and caudal fin with numerous black spots arranged in 3–4 bars.

Description. Morphometric data are given in Table 1 . Body elongate and stout. Dorsal profile gently arched, elevating steeply from tip of snout to nape then evenly to dorsal-fin origin, then horizontal to caudal-fin base. Anterior body oval in cross section, posterior body compressed. Ventral profile of body more or less straight throughout length. Head slightly depressed, body almost as broad as high at nape. Snout length almost half of head length, about two-thirds of eye diameter.

Dorsal fin with 4 simple and 8½ branched rays, articulating nearer to tip of snout, in advance of pelvic-fin origin, its distal margin slightly convex. Anal fin with 3 simple and 6 branched rays, reaches caudal-fin base. Pectoral fin with 1 simple and 11 rays, reaching about half of distance to pelvic-fin base. Pelvic fin with 1 simple and 7 branched rays, origin below base of branched dorsal-fin ray 2 or 3, reaching about two-thirds distance to anal-fin origin; distal margin of pelvic fin reaching vent when adpressed. Axillary pelvic-fin lobe present, prominent. Caudal fin with 9+8 branched rays, deeply emarginated, lobes equal. Caudal peduncle 0.9–1.1 times longer than deep, without dorsal and ventral adipose crests on posterior half. Largest recorded size 61.4 mm SL (MUMF 11120, holotype).

Body covered with partly overlapping minute scales, except between base of pectoral fin and belly. Lateral line complete, straight, with 88–94 pores. Cephalic lateralis system with 9 supraorbital, 3+9 infraorbital, 10 preoperculomandibular, and 3 supratemporal pores. Unculi on lips and barbels.

Anterior nostril pierced in front side of low pointed flap-like tube. Mouth arched, 1.3–1.5 times wider than length. Lip fleshy, upper lip thin and finely pleated with a deep median incision. Lower lip with a median interruption, a wide median furrow ( Fig. 2). Processus dentiformis present, not prominent. No median notch in lower jaw. Inner rostral barbel reaching to vertical of anterior rim of nostril; outer one reaching base of maxillary barbel. Maxillary barbel reaching to posterior rim of occiput. Free posterior chamber of air bladder absent ( Fig. 3 ). Intestine with a large loop behind stomach, extending forward to middle of stomach ( Fig. 4 ).

Sexual dimorphism. Male with prominent suborbital flap. Males slightly longer (59.7–61.4 vs. 55.6–57.1 mm SL) and thinner (body depth at dorsal-fin origin: 17.2–18.1 vs. 19.1–19.6 % SL) than females.

Colour. In fresh specimens: body with 8–9 brown bars on dull white background. Saddles in front of dorsal fin broken up into 2–3 bars as they descend on the sides, making a reticulated appearance. Bars on body just behind dorsal fin broad with narrow interspaces. Head dull white with dark areas on nape, opercle, snout, above dorsal portion of orbit, and between eyes forming prominent vermiculations. A black spot at bases of simple and first branched dorsal-fin rays. Two rows of black spots on each branched dorsal ray; a small one midway to branching point from base, and another elongated spot at branching point of each branched dorsal-fin ray extending towards margin, leaving a small hyaline gap on periphery. Distal margin of anterior dorsal-fin rays golden. Pectoral fin with 2 rows of spots, transversely; one at point where rays divide into branches, another midway between point of branching and distal end of each ray. Anal fin with a row of black spots in middle. Basicaudal bar black, dissociated, with a small spot at dorsal extremity and blotch-like bar from middle to ventral extremity. Two red elongated patches, one each on dorsal and ventral portions of caudal fin, near basicaudal bar. Caudal fin with black spots arranged in 3–4 V-shaped bars with vertices pointed towards caudal base.

Distribution. Known only from Tuirial River, a major tributary of the Barak River in the Barak-Surma- Meghna River system in Mizoram, India ( Fig. 5 ).

Etymology. The specific epithet is derived from the Latin pauci prefix meaning few, and Latin reticulata meaning net-like; an adjective referring to the network of bars on the anterior side of the body.

Figures

FIGURE 1. Schistura paucireticulata, n. sp.: lateral aspects of a. holotype, MUMF 11120, 61.4 mm SL, male (fresh state); b. holotype after preservation; c. dorsal aspect of holotype.

FIGURE 3. Air bladder of Schistura paucireticulata without free posterior chambers. Scale bar = 1 mm.

FIGURE 4. Coiling pattern of intestine of Schistura paucireticulata. Scale bar = 5 mm.

FIGURE 5. Map showing type locality of Schistura paucireticulata.