Mystus carcio (Hamilton)

A. Darshan, N. Anganthoibi & W. Vishwanath, 2010, Redescription of the striped catfish Mystus carcio (Hamilton) (Siluriformes: Bagridae), Zootaxa 2475, pp. 48-54 : 49-51

Mystus carcio (Hamilton)

( Fig. 1 )

Pimelodus carcio Hamilton, 1822: 181 (type locality: ponds in northern parts of Bengal). Pimelodus Batasius Hamilton, 1822 : pl. 23, fig. 60 (figure and caption). Macrones vittatus Day, 1877: 448 , Pl. XCIX Fig. 4 (in part).

Mystus vittatus Shaw & Shebbeare, 1938: 94 , text-fig. 93;

Material examined. MUMF 9518, 9, 30.2–47.9 mm SL, India: Assam: Brahmaputra River at Guwahati , 26°11'59"N, 91°45'0 9"E; M. Shantakumar, 24 May, 2007. ZSI FF4081, 1 ex., 47.9 mm SL, same data as above . MUMF 9519 , 17 , 39.0–47.0 mm SL, same collection site as above, W. Vishwanath & party, 8 May, 2005. ZSI FF4080, 1 ex., 42.9 mm SL, same data as above . MUMF 9533 , 4 , 30.0–48.0 mm SL, wetlands of Comilla district, Bangladesh ( Meghana basin), purchased in Agartala fish market, Tripura, India; W. Vishwanath, 12 October, 2009.

Diagnosis. Mystus carcio differs from other known striped species of Mystus by its small adult size, maturing at 44.0 mm SL; adipose-fin base shorter than or equal to dorsal-fin base (8.5–11.9 % SL); pelvic fin reaching anal-fin origin; pectoral girdle with coracoid shield exposed ventro-laterally below pectoral fin; eyes rounded, large (25.6–30.7% HL), dorsally orientated on head; vomerine tooth-patch interrupted at midline.

Description. Morphometric data are provided in Table 1. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gradually ventrally to end of caudal peduncle. Ventral profile slightly convex up to anal-fin origin, then rising gradually until end of caudal peduncle. Head depressed. Anterior cranial fontanel extending from level of posterior margin of nasal opening to line through posterior orbital margins, separated from posterior fontanel by a narrow epiphyseal bar. Posterior fontanel long, extending almost to base of occipital process. Supraoccipital process narrow, extending up to basal bone of dorsal fin. Eye rounded, large, dorsally orientated on head; in lateral view eye diameter accommodating half of head depth at eye.

Mouth sub-terminal. Villiform teeth present on all tooth-bearing surfaces. Premaxillary tooth-band of equal width throughout, slightly curved backward. Vomerine tooth patch interrupted at midline, as wide as that of premaxillary, its lateral extensions slightly shorter than those of premaxillary. Dentary tooth band at symphysis much broader than those of premaxilla and vomer, tapering laterally towards corners of mouth. Gill opening wide, free from isthmus. First branchial arch with 6+17=23 (2) or 6+18= 24 (2) gill rakers. Vertebrae: 16 +16= 32 (2) or 17+15=32 (2). Ribs: 7 (4). First fully formed haemal canal appears on 10th vertebra. Branchiostegal rays: 8 (4). Skin smooth. Lateral line complete, mid-lateral in position.

Barbels in four pairs, all flattened laterally. Maxillary barbel short, extending to middle of pelvic fin; nasal barbel long, reaching base of occipital process; outer mandibular barbel extending to middle of pectoral-fin spine when adpressed; inner mandibular barbel reaching base of pectoral spine.

Dorsal-fin origin slightly anterior to middle of body, with a spinelet, a spine, and 7 branched rays; spine as long as three-fifths of dorsal-fin height, serrated posteriorly with 9–11 serrae. Adipose fin deeply incised posteriorly, its base shorter than or equal to dorsal-fin base.

Pectoral fin with a spine and 5–7 branched rays; spine stout, curved backwards, with 10–14 strong, large serrae on posterior margin. Pectoral-fin distal margin almost straight. Pelvic fin with i, 5 rays, its distal tip reaching base of anal-fin origin. Anal fin with iii–v, 9–10 rays, originating opposite adipose-fin origin; first two simple rays minute, but visible in cleared and alizarin-stained specimens. Caudal fin deeply forked with i,7+8,i rays, its upper lobe longer, with 10 procurrent rays; lower lobe with 11.

Sexually dimorphic: females with rounded genital papilla. Female of 44.0 mm SL found to bear eggs. Males bear an elongate genital papilla, more prominent, extending beyond anal-fin origin in mature individuals. Males usually smaller than females.

Distribution. India: West Bengal and Assam (Ganga-Brahmaputra drainage), Bangladesh: Meghana basin in Comilla District.

Coloration. In formalin, ground colour of body amber. Snout and supraorbital region dark brown, extending dorsally to posterior end of adipose fin. Three broad, dark-brown stripes on sides of body: the middle stripe with a pale line marking the lateral line, flanked by a dorsolateral and a ventrolateral stripe, with narrower, pale interspaces. Middle stripe originates immediately behind posterolateral corner of head, dorsolateral one from region of epiotic and lateral base of occipital process, ventrolateral one from distal tip of cleithral process. All the three stripes uninterrupted, extending posteriorly up to caudal-fin origin. A darkbrown tympanic spot present above pectoral-fin origin.

Figures

FIGURE 1. Mystus carcio, lateral view, MUMF 9518, 39.0 mm SL.

FIGURE 4. Comparison of skulls, showing cranial fontanel: a. Mystus carcio, MUMF 9518, 46.6 mm SL; b. Mystus tengara, MUMF 9520, 71.5 mm SL; c. Mystus vittatus, MUMF 9527, 72.7 mm SL; d. Mystus tengara, Unregistered, 42.2 mm SL. e = Supraethmoid, le = lateral ethmoid, f = frontal, af = anterior fontanel, pf = posterior fontanel, eb = epiphysial bar, s = sphenotic, pt = pterotic, so = supraoccipital, ex = exoccipital, op = occipital process.