Schistura maculosa, Lalronunga, 2013

Lalronunga, Samuel, 2013, Schistura maculosa, a new species of loach (Teleostei: Nemacheilidae) from Mizoram, northeastern India, Zootaxa 3718 (6), pp. 583-590 : 584-585

Schistura maculosa , sp. nov.

( Fig. 1 )

Type material. Holotype: ZSI FF 4973, 75.3 mm SL; India: Mizoram, Pharsih River, a tributary of Tuivai River (Barak drainage) in the vicinity of Kawlbem , Champhai District , 23°51'58"N; 93°17'20"E; Samuel Lalronunga et al., 20 April 2013.

Paratypes: ZSI FF 4974 (3), 56.9–69.0 mm SL; MZUBM /F. 130021- 130023 (3), 46.4–71.0 mm SL; PUCMF 13010 (8), 33.9–76.0 mm SL ; PUCMF 13011 (4), 57.6–75.6 mm SL (cleared and stained); data as for holotype ; PUCMF 13012 (2), 60.4–68.8 mm SL; India: Mizoram, Tuingo River, a tributary of Tuivai River ( Barak drainage) in the vicinity of Kawlbem , Champhai District , 23°52'40"N 93°19'01"E; Vanlalmalsawma, 25 March 2013 .

Diagnosis. Schistura maculosa differs from other species of the genus from the Ganga-Brahmaputra basin and its adjacent basins by the combination of the following characters: 3–4 rows of black spots horizontally across dorsal-fin; 5–7 more or less organized rows of black spots on rays vertically across caudal-fin; slightly emarginate caudal-fin with 8+8 branched rays; 20–30 narrow black bars on the body; incomplete lateral line extending up to vertical through pelvic-fin origin, with 26–35 pores; males with a sub-orbital flap; and intestine looped behind the stomach.

Description. Biometric data are given in Table 1. Body elongate; dorsal profile rising evenly from tip of snout to level of eye, gradually increasing thereafter to dorsal-fin origin, then sloping gently to end of caudal peduncle. Body cylindrical anteriorly to dorsal-fin origin, becoming increasingly compressed thereafter. Head long, depressed; snout rounded. Eyes ovoid, large, positioned near top of head, slightly anterior towards snout, not visible in ventral view.

Anterior nostril pierced anteriorly, a flap-like tube, not reaching eye, nearer to eye than snout tip. Mouth subterminal, large, moderately arched, its gape (about 1.7–2.0 times) wider than long. Lips thick, fleshy ( Fig 2a ), covered by furrows. Upper lip without median incision. Lower lip with median interruption. Processus dentiformis present. Inner rostral barbel extending to vertical through middle of orbit, outer rostral barbel extending up to ⅓ of distance between orbit posterior margin and opercular posterior margin; maxillary barbel extending slightly farther than outer rostral barbel. Barbels covered with unculi.

Dorsal-fin with 2 (4) or 3 (17) simple and 7½ (21) branched rays, its origin posterior to pelvic-fin origin; its distal margin convex; last unbranched ray shorter than first branched ray. Pectoral-fin sub-acuminate, shorter than head length, with 11 (3) or 12 (4) or 13 (14) rays, its origin slightly anterior to posterior edge of opercle, adpressed fin tip not reaching pelvic-fin base but surpassing midway between its origin and pelvic-fin origin; small tubercles present on dorsal surface of pectoral-fin rays of males, covering branched rays 1–6. Pelvic-fin sub-acuminate, shorter than head length, with 8 (21) rays, its origin anterior to dorsal-fin origin, midway between snout tip and caudal-fin base, adpressed fin tip not reaching anus. Axillary pelvic lobe present at pelvic-fin base. Anal-fin subacuminate with 3 simple and 5½ (21) branched rays, its origin closer to caudal-fin base than pelvic-fin origin. Caudal-fin branched rays 8+8 (21). Caudal-fin slightly emarginate, its lobes sub-equal. Caudal peduncle 1.3 times longer than deep, with very low or no adipose crest.

Entire body covered by minute cycloid scales, deeply embedded, sparse on chest and belly, no scales on head and cheeks. Lateral line incomplete with 26–35 pores, extending to vertical through pelvic-fin origin. Cephalic lateral line system with 8 supraorbital, 4+10 infraorbital, 10 pre-operculomandibular and 3 supratemporal pores. Intestine looped behind stomach ( Fig. 2b )

Vertebrae: 22+13 = 35 (3) or 23 + 13 = 36 (1)

Sexual dimorphism. A prominent sub-orbital flap present in males. Small tubercles present on dorsal surface of pectoral-fin rays in males, covering branched rays 1–6.

Note on biology: A dissected female 75.6 mm SL contained ovulae 0.8–1.2 mm in diameter.

Coloration. In 70% alcohol: Body light-yellowish brown with 20–30 narrow black bars; bars usually bifurcated, narrower than or equal to interspaces; bars posterior to dorsal-fin origin coalesce dorsally; bars reaching to level of pelvic-fin base ventrally, beneath lateral-line scale in smaller specimens. Black basal caudal bar well marked, complete. Dorsal surface of head dark brown. Dorsal-fin hyaline with two black blotches at base, first blotch covering simple and first branched rays, second blotch covering third and fourth or third to fifth branched rays; 3–4 rows of black spots on rays horizontally across the fin; caudal-fin hyaline with 5–7 more or less organized rows of black spots on rays vertically across the fin; 2–4 isolated black spots at upper extremity of caudal-fin. Anal-fin hyaline. Pectoral and pelvic fin hyaline, with dark markings on interradial membrane.

Etymology. The specific name is derived from the Latin for ‘spotted’, referring to the numerous black spots on the caudal and dorsal fins. It is used as an adjective.

Distribution and habitat. The species has been collected only from the Tuingo and Pharsih Rivers, tributaries of Tuivai River, Mizoram, India ( Fig. 3 ). Specimens were collected from a small pool in slow-flowing water. The substrate was composed of sand, gravel and rocks. The ambient temperature varied from 19–26°C (morning to afternoon) and the water pH ranged from 7.8–8.0. The species was associated with Exostoma cf. barakensis, Garra spp. and Lepidocephalichthys guntea .

Figures

FIGURE 1. Schistura maculosa; a) holotype, ZSI FF 4973, 75.3 mm SL; lateral, dorsal and ventral view; (b) paratype, ZSI FF 4974, 56.9 mm SL, lateral view; c) paratype, PUCMF 13010, 33.9 mm SL, lateral view.

FIGURE 3. Map showing the collection locality of Schistura maculosa (circle); n.b., a circle indicates more than a single locality.

FIGURE. 2. Schistura maculosa; a) paratype, ZSI FF 4974, 69.0 mm SL, ventral view of head; b) paratype, PUCMF 13011, 75.6 mm SL, digestive tract. Scale bars = 1 mm.