Mystus seengtee (Sykes, 1839)

Prosanta Chakrabarty & Heok Hee Ng, 2005, The identity of catfishes identified as Mystus cavasius (Hamilton, 1822) (Teleostei: Bagridae), with a description of a new species from Myanmar., Zootaxa 1093, pp. 1-24 : 9-13

Mystus seengtee (Sykes, 1839)

(Figs. 5-6)

Pimelodus seengtee Sykes, 1839 : 164 (type locality: Dukhun, India, probably Bhima River at Pargaon) ; Sykes, 1841: 374, Pl. 66 Fig. 2.

Bagrus cavasius (non Hamilton) Jerdon, 1849: 337.

Macrones cavasius (non Hamilton) Günther, 1864: 76 (in part); Day, 1865a: 290; Day, 1877: 447, Pl. C Fig. 1 (in part); Day, 1889: 155 (in part).

Hypselobagrus cavasius (non Hamilton) Day, 1865b: 188.

Mystus cavasius (non Hamilton) Hora, 1936: 1; Hora, 1937: 17; Silas, 1949: 793; Rajan, 1955: 45; Jayaram, 1981: 196, Fig. 92A (in part); Jayaram et al., 1982: 84, Fig. 23; Talwar & Jhingran, 1991: 559, Fig. 184 (in part); Raghunathan, 1993: 336; Roberts, 1994: 248 (in part); Jayaram, 1995: 97; Shaji et al., 1995: 361; Jayaram, 1999: 235, Fig. 118C (in part); Menon, 1999: 200 (in part); Jayaram & Anuradha Sanyal, 2003: 46, Fig. 5 (in part); Yadav, 2003: 18.

Mystus (Mystus) cavasius (non Hamilton) Jayaram, 1954: 532, Fig. 2 (in part); Misra, 1976: 87, Fig. 18 (in part).

Mystus cavasus [sic.] (non Hamilton) Jadhav & Bhosale, 1996: 76.

Material examined. CAS 62005 (5), 71.3-128.0 mm SL; India: Karnataka, Cauvery River drainage, 9 km north of Kushalnagar (about 80 km WNW of Mysore). CAS 62027 (12), 56.3-109.8 mm SL; India: Karnataka, Cauvery River drainage, NW/WNW of Mysore. CAS 62078 (8), 91.9-152.6 mm SL; India: Karnataka, Krishna River drainage, Tungabahdra River and Reservoir at Hospet, Hampi, and Kampli.

Diagnosis. Mystus seengtee differs from other congeners with a long-based adipose fin (except M. cavasius and M. falcarius ) in having a combination of a black spot in front of the dorsal-spine base, a dark humeral mark, a body without distinct midlateral stripes, very long maxillary barbels reaching to caudal-fin base, dorsal spine short and feebly serrate, tall dorsal fin, and 23-28 rakers on the first gill arch. It can be distinguished from M. cavasius in having more rakers on the first gill arch (23-28 vs. 13-22; Table 1) and a more steeply sloping predorsal profile (making an angle of 30-35° to the horizontal vs. 20-25°; Fig. 2), and from M. falcarius in having a straight or gently concave (vs. markedly concave) dorsoposterior margin of the dorsal fin (Fig. 3), an ovoid (vs. crescentic) dark humeral mark and a faint (vs. very prominent) dark spot at the base of the dorsal spine.

Description. Biometric data are given in Table 3. Head depressed; dorsal profile evenly sloping (at angle of 30-35° to horizontal) and ventral profile almost straight. Bony elements of dorsal surface of head covered with thin skin; bones readily visible, especially on posterior half of neurocranium, and ornamented with numerous fine, radial grooves. Anterior cranial fontanelle extending from behind snout to line through posterior orbital margins, separated from posterior fontanelle by narrow epiphyseal bar. Posterior fontanelle extending to base of supraoccipital spine. Supraoccipital spine elongate, slender and with blunt tip; extending to anterior nuchal plate. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head. Gill openings wide, extending from exposed surface of posttemporal to beyond isthmus at line through mouth corners. Gill membranes free from isthmus. First branchial arch with 23-28 long, slender gill rakers.

Mouth subterminal, fleshy upper lip extending anteriorly beyond upper jaw. Oral teeth small and villiform, in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band rounded, of equal width throughout. Dentary tooth band much narrower than premaxillary tooth band at symphysis, tapering laterally. Vomerine tooth band unpaired, continuous across midline; smoothly arched along anterior margin, tapering laterally to point extending posteriorly well past level of premaxillary band; band width narrower than premaxillary band at midline, widening laterally and then tapering to a sharp point posterolaterally.

Barbels in four pairs. Maxillary barbel long and slender, extending beyond caudal-fin base. Nasal barbel slender, extending to vertical through base of pectoral spine. Inner mandibular-barbel origin close to midline; thicker and longer than nasal barbel and extending to base of posteriormost pectoral-fin ray. Outer mandibular barbel originating posterolateral of inner mandibular barbel, extending to vertical through middle of dorsalfin base.

Body moderately compressed. Dorsal profile rising evenly but not steeply from tip of snout to origin of dorsal fin and sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile slightly convex to anal-fin base, then sloping slightly dorsally to end of caudal peduncle. Skin smooth. Lateral line complete and midlateral in position. Vertebrae 21+19=40 (1), 22+19=41 (4), 23+18=41 (1) or 23+19=42 (7).

Dorsal fin with spinelet, spine, and 6 (2) or 7 (11) rays. Origin of dorsal fin anterior to mid-body, about one-third of body. Dorsal fin margin straight or slightly concave, with first two fin rays longer than others. Dorsal fin spine moderately long, straight and slender, posterior edge with 3-4 indistinct serrations. Serrations fewer, lower and less distinct in smaller specimens. Anterior nuchal plate acutely triangular.

Pectoral fin with stout spine, sharply pointed at tip, and 7 (4), 8 (6) or 9 (3) rays. Anterior spine margin smooth; posterior spine margin with 11-16 serrations along entire length (serrations fewer in smaller specimens). Pectoral fin margin straight anteriorly, convex posteriorly. Postcleithral (humeral) process short and slender, with straight dorsal edge and extending to anterior tip of anterior nuchal plate.

Pelvic fin origin at vertical through posterior end of dorsal-fin base, with i,5 (13) rays and slightly convex margin; tip of adpressed fin not reaching anal fin origin. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Males with a short genital papilla reaching to base of first anal-fin ray.

Adipose fin with very long base and deeply-incised posterior portion, spanning almost all of postdorsal distance. Anal fin origin located at approximately middle third of adipose fin, fin with iv,6 (4), iv,7 (7), iv,8 (1) or iv,9 (1) rays and curved posterior margin.

Caudal peduncle moderately deep. Caudal fin deeply forked, with i,6,7,i (1), i,7,7,i (6) or i,7,8,i (6) principal rays; upper lobe slender and lanceolate, lower lobe pointed. Procurrent rays extending only slightly anterior to fin base.

Coloration. In 70% ethanol: dorsal surface of head and body uniform brownish gray. Dark spots in front of base of dorsal spine and on humeral region, indistinct in most specimens. Ventral surfaces of head and body dirty white; adipose fin brownish gray. All fins hyaline, with melanophores on fin membranes on some individuals, usually more densely aggregated along margins with fin rays. Dorsal half of barbels gray dorsally, gradually turning to dirty white on ventral half and tips.

Distribution. Known from the Krishna and Cauvery river drainages in southern India (Fig. 4). Mystus seengtee is very likely to be found in most (if not all) other river drainages south of the Krishna River drainage.