Mystus velifer, Ng, 2012

Ng, Heok Hee, 2012, Mystus velifer, a new species of catfish from Indochina (Teleostei: Bagridae), Zootaxa 3398, pp. 58-68 : 59-63

Mystus velifer , sp. nov.

( Figs. 1, 2a, 3a, 4a, 5)

Hypselobagrus wolffi (non Bleeker)— Bleeker, 1864: 357; 1865: 175; Sauvage, 1881: 161.

Macrones wolffi (non Bleeker)—von Martens, 1876: 400; Weber & de Beaufort, 1913: 340 (in part); Hora, 1923: 171; Suvatti, 1950: 299.

Mystus wolfii (non Bleeker)— Fowler, 1934: 95.

Mystus wolffii (non Bleeker)— Fowler, 1935: 104, Fig. 29; 1937: 148; 1939: 44; Desoutter, 1975: 447; Suvatti, 1981: 93; Kottelat, 1985: 270; Mai et al., 1992: 189; Truong & Tran, 1993: 215, Fig. 93; Vidthayanon et al., 1997: 43; Nguyen, 2005: 364, Fig. 186.

Mystus wolffi (non Bleeker)— Smith, 1945: 383; Mai & Nguyen, 1988: 49; Rainboth, 1996: 144; Fig. 146; Lime et al., 1999: 382; Gaanantkul et al., 2000: 33.

Mystus sp. cf. wolffi — Rainboth, 1996: 144.

Mystus armiger (non Ng)— Vidthayanon, 2008: 122, Fig. 161; Jutagate et al., 2011: 50; Sakset et al., 2012: 181.

Type material. Holotype: UMMZ 232733 , 67.8 mm SL; Cambodia: Kompong Thom Province, Tonlé Sap at exit to Great Lake , 4 km NW of Chhnok Trou, at Kompong Thom fishing lot 2; W. J. Rainboth, N. van Zalinge & R Chan, 28 February 1995.

Paratypes: ANSP 76829 (5), 119.8–136.9 mm SL; Thailand: Krabi Province, Krabi ; R. de Schauensee collectors, 24 September 1936 . ANSP 89484 (6), 130.2–144.8 mm SL; Thailand: Krabi Province, Krabi ; R. de Schauensee collectors, 21 September 1936 . CAS 55855 (2), 68.0– 84.2 mm SL; Thailand: Chachoengsao Province, Bang Pakong River at Bang Pakong village , in tidal region along mangrove and nipa palm swamp, 13°29'45"N 100°59'15"E; H. A. Fehlmann et al., 6 December 1957 . UMMZ 181263 (2), 91.8–100.8 mm SL; Cambodia: Pursat Province, Tonlé Sap at Kompong Luong , 12°35'N 104°11'E; J. Bardach, 18 March 1959 . UMMZ 197036 (79), 28.6–86.9 mm SL; Thailand: Phatthalung Province, Songkhla Lake , off Phatthalung; K. F. Lagler et al., 6 January 1965 . UMMZ 214340 (27), 28.1–81.1 mm SL; Vietnam: Phong Dinh Province, Bassac River adjacent to Dong Phu ; R. E. Arden & O. K. Minh, 31 October 1974 . UMMZ 217918 (34), 49.8–74.3 mm SL; Vietnam: Tien Giang Province, Vam Ky Hon , 10°20'23"N 106°24'9"E; local fishermen, 19 June 1974 . UMMZ 227499 (2), 67.0– 69.1 mm SL; Vietnam: Phong Dinh Province, Can Tho River, Mekong River main channel, three trawls encircling Can Tho Island ; R. Johnson & W. J. Rainboth, 24 June 1974 . UMMZ 232131 (5), 55.4–63.5 mm SL; Cambodia: Kandal Province, Tonlé Sap River 35 km upstream from Phnom Penh, dai row 1, net A, 11°52'N 104°47'E; W. J. Rainboth et al., 16 January 1995 . UMMZ 232222 (1), 59.0 mm SL; Cambodia: Kandal Province, Tonlé Sap River 22 km upstream from Phnom Penh, 11°44'N 104°50'E; W. J. Rainboth, N. van Zalinge & S Lieng, 16 January 1995 . UMMZ 232546 (2), 54.1–64.1 mm SL ; UMMZ 249560 , 64.2 mm SL; Cambodia: Kandal Province, Tonlé Sap dai net series 8 and 9, 11°44'N 104°50'E; W. J. Rainboth & R. Chan , 13 February 1995 .. UMMZ 234386 (1), 56.4 mm SL; Cambodia: Kandal Province, Tonlé Sap at dai fishery row 9, 25 km upstream from Phnom Penh ; W. J. Rainboth et al., 22 January 1996 . UMMZ 235727 (2), 62.4–63.7 mm SL; Cambodia: Kandal Province, fishing lot 8, 35 km upstream from Phnom Penh , 11°44'N 104°50'E; W. J. Rainboth & C Yim, 1 March 1996 . ZRC 53463 (7), 67.2–98.1 mm SL; Thailand: Phatthalung Province, Ban Thale Noi , 7°46'23.4"N 100°7'0.4"E; H. H. Tan et al., 26 October 1998 .

Diagnosis. Mystus velifer can be distinguished from congeners except M. wolffii in having a short-based adipose fin (13.0–17.9% SL) and very long maxillary barbels that reach to or beyond the base of the caudal fin. It differs from M. wolffii in having a more produced, narrower snout ( Figs. 2, 3), a larger eye (23.3–29.2% HL vs. 16.8–23.8), fewer rakers on the first gill arch (22–29 vs. 32–41), and the first dorsal-fin ray produced and reaching to the middle of the adipose-fin base (vs. not produced and reaching to origin of the adipose fin; Fig. 4). It differs from M. gulio in having a shorter head (24.1–27.6% SL vs. 27.5–31.6), longer maxillary barbels (reaching beyond anal-fin origin and frequently to base of caudal fin vs. reaching between pelvic- and anal-fin bases), the (anterior) cranial fontanel reaching past (vs. not reaching) midway between the posterior orbital margin and the base of the supraoccipital spine, longer dorsal spine (16.6–21.2% SL vs. 11.4–16.5), adipose fin with a longer base (13.0–17.9% SL vs. 7.7–11.5) and without (vs. with) a deeply incised posterior margin, and more slender caudal peduncle (8.3–11.1% SL vs. 10.6–13.0).

Description. Morphometric data as in Table 1. Head depressed; dorsal profile slightly convex 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. Midline of cranium with elongate fossa extending from behind snout almost to base of supraoccipital spine. Supraoccipital spine elongate, with gently converging sides and blunt tip; extending to interneural shield. Eye ovoid, horizontal axis longest, with free margin; located entirely in dorsal half of head. Gill openings wide, extending from posttemporal to beyond isthmus. Gill membranes free from isthmus, with 9 (27) branchiostegal rays. First branchial arch with 5+17=22 (2), 6+16=22 (2), 7+15=22 (1), 4+20=24* (1), 6+18=24 (2), 7+17=24 (3), 7+18=25 (2), 8+17=25 (1), 6+20=26 (2), 7+19 =26 (2), 7+20=27 (1), 8+19=27 (1), 7+21=28 (1), 7+22=29 (1) or 8+21=29 (1) long, slender gill rakers.

Mouth subterminal, fleshy upper lip extending anteriorly beyond upper jaw. Oral teeth small and viliform, 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. Nasal barbel slender, extending to two-thirds of distance between posterior orbital margin and nuchal plate. Inner mandibular-barbel origin close to midline; barbel thicker and longer than nasal barbel and extending just beyond base of last pectoral fin ray. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending to base of first pelvic fin ray.

Body slightly compressed, becoming more so toward caudal peduncle. 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 19+19=38 (3), 19+20=39 (1), 20+19=39* (11), 21+18=39 (2), 20+20=40 (7), 21+19=40 (2) or 21+20=41 (1).

Dorsal fin with spinelet, spine, and 7 (27) rays. Origin of dorsal fin slightly anterior to midline. Dorsal fin margin convex, with first soft ray longer than other rays and often produced to reach to middle of adipose-fin base when adpressed against body. Dorsal fin spine short, straight and slender, posterior edge with 0–8 serrations. Serrations fewer, lower and less distinct (or often absent) in smaller specimens. Interneural shield narrow, tapering to acutely rounded tip anteriorly.

Pectoral fin with stout spine, sharply pointed at tip, and 7,i (9) or 8 (18) rays. Anterior spine margin smooth; posterior spine margin with 7–17 large serrations along entire length (serrations fewer in smaller specimens). Pectoral fin margin straight anteriorly, convex posteriorly.

Pelvic fin origin at vertical through posterior end of dorsal-fin base, with i,5 (27) 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 not reaching to base of first anal-fin ray.

Adipose fin with convex margin for entire length and with deeply-incised posterior portion; length of base approximately equal to length of anal-fin base. Anal fin base ventral to posterior half of adipose fin, with iv,8 (4), iv,8,i* (2), iv,9 (1), v,8 (12), v,8,i (1) and v,9 (7) rays and curved posterior margin.

Caudal peduncle moderately deep. Caudal fin deeply forked, with i,7,8,i (27) principal rays; upper lobe slender and lanceolate, lower lobe pointed. Procurrent rays extend only slightly anterior to fin base.

Coloration. In 70% ethanol: Dorsal surface of head and body uniform gray or silvery (brownish in some preserved specimens). Ventral surfaces of head and body dirty white; adipose fin brownish or gray. All fins hyaline; median fins with faint dusky distal margins. Dorsal half of barbels gray at base, gradually turning to dirty white on ventral half and tips. Live coloration similar ( Fig. 5).

Distribution. Known from the lower Mekong River drainage (upstream to the Tonlé Sap) westwards and southwards to Songkhla Lake in Peninsula Thailand. This includes the majority of river drainages debouching into the Gulf of Thailand such as the lower Bang Pakong, Chao Phraya, Mae Khlong and Tapi river drainages ( Fig. 6).

Etymology. From the Latin adjective velifer, meaning sail bearing (Latin velum=sail and fero=to bear). The name refers to the relatively elongate first dorsal-fin ray of this species, a diagnostic character.