Bagarius vegrandis, Ng & Kottelat, 2021

Ng, Heok Hee & Kottelat, Maurice, 2021, Description of Bagarius vegrandis, a new species of sisorid catfish from Indochina (Actinopterygii: Siluriformes), with notes on the identity of Bagarius bagarius, Zootaxa 4926 (1), pp. 134-146 : 135-139

Bagarius vegrandis , new species

( Figs. 1 & 2 )

Holotype. UMMZ 209290, 152.9 mm SL; Thailand: Nakhon Phanom province, Mekong River at Ban Tha Kai , 21 km downstream of Mukdahan, 16 km E of Mukdahan by road, 16°27’N 104°51’E; Y. Dhammigbavorn & S. Sairaj, 10 February 1975.

Paratypes. UMMZ 240608 (1 alc.), 82.5 mm SL+(1c&s), 93.1 mm SL; Laos: Luang Prabang province, Nam Nga about 3 km upstream from confluence with Nam Ou , 20°22’N 102°23’E; W. J. Rainboth, D. Y. Mai & D. Singhanouvong, 6 March 1997 . CMK 13900 (1), 112.7 mm SL; Laos: Louang Phabang province, Nam Xuang at confluence with Mekong River at Ban Pak Xuang , 19°58’05”N 102°14’27”E; M. Kottelat, 7 May 1997 . ANSP 59293 (1) 170.0 mm SL ; ZRC 56684 (1), 148.4 mm SL; Thailand: Chieng Mai , on the Mae Nam Ping, 724 km N of Bangkok ; R. M. de Schauensee , 15 December 1932 . UMMZ 209284 (1), 140.4 mm SL; Thailand: Nong Khai province, Tha Bo district, Mekong River backwaters at Ban Tha Sadet , 17°52’36”N 102°35’30”E; E. D. Buskirk, 4 November 1975 . UMMZ 209288 (2 alc.), 79.1–83.5 mm SL+(1 c&s), 91.5 mm SL; Thailand: Mekong River and tributaries on Thai side from Ban Dan to Nakhon Phanom, 17°51’N 104°17’E; K. F. Lagler et al., March 1975 . UMMZ 209934 (1), 120.7 mm SL; Thailand: Nong Khai province, Kum Kang Moo, creek mouth into Mekong River , 17°50’42”N 102°35’20”E; E. D. Buskirk, 30 September 1975 . ZRC 56603 (10), 72.5–112.3 mm SL; Thailand: Nakhon Phanom province, Mae Nam Songkhram , 17°40’N 104°13’E; K. Udomritthiruj, August 2009 . UMMZ 209287 (1), 133.8 mm SL; Thailand: Nakhon Phanom province, Mekong River 3 km downstream of Nakhon Phanom, 17°20’29”N 104°48’13”E; Y. Dhammigbavorn & S. Sairaj, 5 August 1975 . ZRC 46010 (1), 183.0 mm SL; Thailand: Nakhon Phanom province, That Phanom market, 16°57’N 104°43’E; Y.-X. Cai & Y. Y. Goh, 17 June 1998 . UMMZ 241762 (1), 94.9 mm SL; Laos: Savannakhet province, Savannakhet market, 16°35’N 104°45’E; W. J. Rainboth, 1 April 1998 . CMK 13830 (11), 56.4–109.0 mm SL; Laos: Savannakhet province, Mekong River at Ban Donsen , about 6 km S of Savannakhet, 16°30’45”N 104°45’47”E; M. Kottelat, 3 May 1997 . ANSP 178857 (11), 60.1–215.8 mm SL; Thailand: Nakhon Sawan province, Mae Nam Chao Phraya and tributaries in the vicinity of Phayuha Khiri , 15°27’14”N 100°8’3”E; M. H. Sabaj et al., 16 February 2001 . CMK 15586 (1), 131.2 mm SL; Laos: Attapeu province, Xe Kong between Attapeu and downstream to Ban Ouk , 14°44’51”N 106°43’59”E; M. Kottelat et al., 20 May 1999 . UMMZ 238534 (1), 85.5 mm SL; Cambodia: Stung Treng province, Stung Treng market, 13°31’N 105°58’E; W. J. Rainboth et al., 31 January 1996 . UMMZ 235532 (1), 73.7 mm SL; Cambodia: Stung Treng province, Srepok River upstream from bridge on road from Stung Treng to Ratanakiri, 13°26’N 106°36’E; W. J. Rainboth et al., 21 January 1996 .

Additional material. UMMZ 250338 (3), 58.1–84.3 mm SL; Laos: Luang Prabang province, Nam Xuang at Ban Pak Xuang , 19°58’12”N 102°14’44”E; W. J. Rainboth et al., 5 March 1997 . ANSP 59295 (2) 107.9.0– 147.7 mm SL; Thailand: Chieng Mai, on the Mae Nam Ping ; R. M. de Schauensee, 1933 . UMMZ 209285 (1), 90.0 mm SL; Thailand: Nakhon Phanom province, Mekong River 2 km downstream from Nakhon Phanom, 17°20’15”N 104°48’18”E, Y. Dhammigbavorn & S. Sairaj, 4 August 1975 . UMM 209289 (1), 67.0 mm SL; Thailand: Nakhon Phanom province, Mekong River 1 km downstream of Ban Tha Kai , 27 km downstream of Mukdahan, 16°21’13”N 104°53’42”E; Y. Dhammigbavorn & S. Sairaj, 2 August 1975 . UMMZ 209286 (1), 80.2 m SL; Thailand: Ubon Rachathani province, Mekong River at Khemmarat in front of river patrol station S of town, 16°1’42”N 105°19’53”E; W. J. Rainboth et al., 8 April 1975 . UMMZ 209292 (1), 44.8 mm SL Thailand: Ubon Ratchathani province, Khong Chiam district, Mun River at Ban Dan , 3 km upstream from confluence with Mekong River , 15°18’02”N 105°29’16”E; S. Sontirat & E. D. Buskirk, 10 July 1975 . UMMZ 209293 (1), 54.1 mm SL Thailand: Ubon Ratchathani province, Khong Chiam district, Mun River at Ban Dan , 3 km upstream from confluence with Mekong River , 15°18’02”N 105°29’16”E; S. Sontirat & E. D. Buskirk, 11 July 1975 . UMMZ 186793 (2), 79.5–97.2 mm SL; Thailand: Ubon Ratchathani province, market at Ubon Ratchathani; K. F. Lagler et al., 11 February 1965 . UMMZ 209291 (1), 40.3 mm SL; Thailand: Ubon Ratchathani province, Mun River , just S of Ubon Ratchathani, 15°14’3”N 104°53’42”E ; R. E. Arden & Y. Dhammigbavorn, 14 August 1975 .

Diagnosis. Bagarius vegrandis is distinguished from all congeners in having a small maximum body size (to 220 mm SL vs. 520–1400 mm SL) and the adipose-fin origin markedly posterior to (vs. at vertical through or very slightly posterior to) the anal-fin origin. It further differs from congeners in having the following unique combination of characters: ovoid unculiferous plaques on dorsal surface of head, lateral margin of frontal not significantly deflected dorsally, eye diameter 11–15% HL, interorbital distance 23–28% HL, head width 18.3–22.3% SL, head depth 11.1–14.1% SL, filamentous extensions to first pectoral-fin element reaching to anus, dorsal spine width 10.6–13.9 times in its length, body depth at anus 8.7–12.0% SL, neural spines of the 4–6 vertebrae immediately anterior to adipose fin distally flattened but not forming series of prominent bumps along dorsal midline, length of adipose-fin base 10.8–13.0% SL, caudal-peduncle length 19.0–22.4% SL, caudal-peduncle depth 3.2–4.2% SL, 19–20 preanal vertebrae, and 39–40 total vertebrae.

Description. Morphometric data in Table 1. Head depressed; body subcylindrical, becoming more laterally compressed at caudal peduncle. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile straight to anal-fin base, then sloping gently dorsally from anal-fin base to end of caudal peduncle.Anus and urogenital openings located approximately midway between base of last pelvic-fin ray and base of first anal-fin ray. Skin tuberculate, with tubercles of varying sizes on sides of body; larger tubercles loosely arranged in longitudinal rows along dorsal and dorsolateral surfaces of body. Lateral line complete and midlateral. Vertebrae 20+19=39 (1), 20+20=40* (4) or 21+21=42 (1).

Head depressed and broad, triangular when viewed laterally. Snout prominent. Anterior and posterior nares large and separated only by base of nasal barbel. Gill opening broad, extending from ventral margin of post-temporal to isthmus. First branchial arch with 1+5 (2), 2+5 (1), 1+7 (1), 2+6* (4) or 2+7 (3) rakers. Bony elements of dorsal surface of head covered with thick skin, with ovoid unculiferous plaques. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head.

Barbels in four pairs. Maxillary barbel subtended by large skin flap along posterior edge of proximal half of barbel; extending to middle of pectoral-fin base. Nasal barbel short and slender, extending to posterior margin of posterior nares. Inner mandibular-barbel extending to one-third of distance between its base and that of pectoral spine. Outer mandibular barbel extending to two-thirds of distance between its base and that of pectoral spine.

Mouth inferior, premaxillary tooth band partially (approximately one-quarter) exposed when mouth closed. Oral teeth caniniform and of varying sizes, in irregular rows on all tooth-bearing surfaces. Premaxillary teeth appearing in single broad semilunate band. Dentary teeth in two semi-crescentic bands separated at midline.

Dorsal fin located above anterior third of body, with I,6 (18) rays; fin margin concave; spine short and straight, smooth on anterior margin; posterior margin smooth in some individuals and with up to 6 low asperities on others. Adipose fin with anterior margin straight or slightly concave and posterior margin straight; origin markedly posterior to anal-fin origin. Caudal fin strongly forked, with upper lobe longer than lower lobe and i,7,7,i* (10) or i,7,8,i (8) principal rays. Procurrent rays symmetrical and extending only slightly anterior to fin base. Anal fin with straight anterior margin and straight or slightly concave posterior margin; with iii,9 (1), iv,8 (5), iv,6,iii (1), iii,9,i (2), iv,8,i* (4) or iv,9 (5) rays. Pelvic-fin origin at vertical through posterior limit of dorsal-fin base. Pelvic fin with slightly convex margin and i,5 (18) rays; tip of adpressed fin not reaching anal-fin origin. Pectoral fin with I,9* (1), I,9,i (8), I,10 (3), I,10,i (4), I,11 (1) or I,11,i (1) rays; posterior fin margin slightly concave. Pectoral-fin spine with filamentous extensions reaching just beyond base of last pelvic-fin ray; anterior margin of spine smooth, posterior margin with 9–19 (holotype =11) serrations.

Coloration. In 70% ethanol: dorsal, lateral and ventral surfaces of head and body dark yellow, with three medium-brown saddles: first below dorsal fin, second below adipose fin, and third at posterior third of caudal peduncle. Small, medium-brown spots randomly scattered over dorsal and lateral surfaces of head and body in some individuals. Dorsal fin dark yellow, with medium brown base and irregular, subdistal medium brown band along upper one-half to one-third of fin. Pectoral fin dark yellow with scattered medium brown melanophores. Pelvic fin dark yellow, with medium brown base and thin irregular medium brown band across middle of fin. Anal fin hyaline, with medium brown base and irregular, thin medium brown band along middle of fin. Caudal fin dark yellow, with diffuse irregular medium brown spot at base of each caudal lobe and subdistal W-shaped medium brown band. All barbels dark yellow. Live coloration similar, except with more yellow ( Fig. 2 ).

Etymology. The Latin adjective vegrandis means “not very large”, and the name is applied in reference to the small body size of this species in comparison to its congeners.

Distribution. Known from the Chao Phraya and Mekong River drainages in Thailand, Laos and Cambodia, with its presence also expected in Vietnam ( Fig. 3 ).

Figures

FIGURE 1. Bagarius vegrandis, holotype, UMMZ 209290, 152.9 mm SL; Thailand: Mekong River. Dorsal, lateral and ventral views.

FIGURE 2. Bagarius vegrandis, approx. 300 mm TL; Thailand: Phitsanulok province, Yom River (specimen not preserved), showing live coloration. Photograph courtesy of Nonn Panitvong.

FIGURE 3. Collection localities of Bagarius vegrandis examined in this study.