Glyptothorax mibangi, Darshan, Achom, Dutta, Rashmi, Kachari, Akash, Gogoi, Budhin & Das, Debangshu Narayan, 2015

Darshan, Achom, Dutta, Rashmi, Kachari, Akash, Gogoi, Budhin & Das, Debangshu Narayan, 2015, Glyptothorax mibangi, a new species of catfish (Teleostei: Sisoridae) from the Tisa River, Arunachal Pradesh, northeast India, Zootaxa 3962 (1), pp. 114-122 : 116-118

Glyptothorax mibangi , new species ( Fig. 1 )

Type material. Holotype: RGUMF 243, 79.0 mm SL; India: Arunachal Pradesh State, Tisa River near Longding, Brahmaputra River basin, 26°52'N, 95°21'E, D.N. Das & party, 18 October 2008.

Paratypes: RGUMF 244–245 (2), 75.9–83.5 mm SL; same data as holotype; RGUMF 245, 83.5 mm SL, partially dissected for vertebral count.

Diagnosis. Glyptothorax mibangi can be distinguished from its congeners in the Ganga–Brahmaputra and Barak– Surma–Meghna basins by the following combination of characters: an obtuse, leaf-shaped thoracic adhesive apparatus with a spindle-shaped median depression, skin ridges present over entire apparatus, including the depressed region; ventral surface of pectoral spine and first pelvic-fin ray non-plaited; body slender with a depth of 10.4–13.5% SL; caudal peduncle shallow with a depth 6.8–8.3% SL; snout long with 52.9–58.6% HL; and 2+7 gill rakers on the first branchial arch.

TABLE 1. Morphometric data of holotype and paratypes of Glyptothorax mibangi (n=3) and G. gracilis (n=7). * including the data of ZSI/NRSV-988. G. mibangi G. mibangi G. mibangi G. gracilis G. gracilis

Holotype Paratype Paratype

RGUMF 243 RGUMF 244 RGUMF 245 ZSI/NRS range*

V-988

Description. Morphometric data are given in Table 1. Body elongate, compressed laterally towards posterior region; dorsal profile rising evenly from tip of snout to dorsal-fin origin, then sloping gently ventrad from dorsalfin origin to end of caudal-peduncle. Ventral profile flat to anal-fin origin, then gradually sloping dorsad from analfin origin to end of caudal peduncle. Anus and urogenital openings at posterior half of adpressed pelvic fin. Skin granular, granules more prominent on dorsal surface of neurocranium. Lateral line complete, midlateral in position. Head depressed, longer than broad, triangular in lateral view. Snout slightly pointed in lateral aspect. Mouth inferior, lips broad, upper jaw longer than lower jaw, upper lip continuing into maxillary barbel. Oral teeth small, villiform, in irregular rows, borne on all tooth-bearing surfaces. Palate edentate. Premaxillary tooth-band exposed partially with mouth closed, teeth arranged in single, broad, semilunate band. Dentary teeth in two crescentic patches separated at midline by narrow gap. Anterior and posterior nares separated only by base of nasal barbel. Eye ovoid. Gill opening wide, extending from beneath post-temporal to isthmus. Occipital process not reaching anterior tip of nuchal plate of dorsal fin. First branchial arch with 2+7 (1) gill rakers. Thoracic adhesive apparatus well-developed, obtuse, leaf-shaped, with a median spindle-shaped depression; skin ridges present over entire apparatus, including depressed region. Vertebrae 17+18 = 35 (1).

Barbels in four pairs; nasal barbel arising from internarial septum, just reaching anterior margin of eye when adpressed; maxillary barbel supported by large flap of skin, extending slightly beyond end of pectoral-fin base; outer mandibular barbel longer than inner, reaching base of first pectoral-fin ray, inner mandibular barbel short, slightly less than horizontal length of eye.

Dorsal fin with I,6 (3) rays, inserted nearer to snout tip than to caudal-fin origin, its distal margin concave. Dorsal spine long, straight and rigid, with anterior margin smooth and posterior margin weakly serrated bearing 4 (1) or 6 (2) serrae. Pectoral fin with I,10 (2), or I,11 (1) rays, extending past dorsal-fin base, almost reaching pelvic fin origin when adpressed. Pectoral spine broad, its anterior margin smooth, posteriorly serrated, with 11 (2) serrae. Ventral surfaces of spine and adjacent branched ray of pectoral fin non-plaited. Pelvic fin with i,5 rays (3), first ray originating at vertical behind dorsal-fin base, tip of adpressed fin not reaching anal-fin origin. Ventral surfaces of simple ray and adjacent branched ray of pelvic fin non-plaited. Anal-fin with ii,10 (1) or ii,11 (2) rays, its origin located slightly anterior to vertical through adipose-fin origin, anterior fin margin straight, posterior margin slightly concave. Adipose-fin base length shorter than dorsal-fin base, its anterior margin straight, inclined at an angle of about 33° from mid-dorsal line, posterior margin angular. Caudal fin with i,7,8,i (3) principal rays, fin deeply forked, lower lobe slightly longer than upper.

Coloration. In 70% ethanol: dorsal and lateral surfaces of head and body uniformly brown, ventrally pale brown. Thin, yellowish mid-dorsal stripe. Skin over occipital spine, anterior tip of nuchal plate and third nuchal plate pale yellow. A narrow, pale-yellow line superimposed on lateral line. Base and distal third quarter of dorsal and pectoral fins with dark-brown bands. Adipose fin with large dark-brown blotch. Caudal-fin dark-brown at base. Pelvic and anal fins with faint brown band midway between base and distal tip of the fins, against amber background.

Distribution. Known only from the Tisa River, Brahmaputra basin ( Fig. 2 ).The type locality is a fast flowing hill stream with a substrate of boulders, cobble, pebbles and sand. Cobbles dominate the substrate composition of the stream ( Fig. 3 ).

Etymology. The species is named after Tamo Mibang, Vice-Chancellor of Rajiv Gandhi University, Doimukh, whose patronage has continually been extended to freshwater-fish research and conservation in the Eastern Himalyan region of India.

Figures

FIGURE 1. Glyptothorax mibangi, holotype, RGUMF 243, 79.0 mm SL; a) dorsal, b) lateral and c) ventral views. India: Arunachal Pradesh: Tisa River near Longding.

FIGURE 2. Type locality of Glyptothorax mibangi (star).

FIGURE 3. Type locality of Glyptothorax mibangi (Tisa River). Photograph courtesy of P. J. Saikia.