Barilius signicaudus, Tejavej, 2012

Tejavej, Anuratana, 2012, Barilius signicaudus, a new species of cyprinid fish from Maeklong Basin, western Thailand (Cypriniformes: Cyprinidae), Zootaxa 3586, pp. 138-147 : 140-144

Barilius signicaudus new species

( Figs. 1A–C, 2A, 3A, 6A)

Barilius ornatus Sauvage 1883: 153–154 (type locality: Menam, Siam).

Holotype. UNMF 07541 , 80.1 mm SL, Sangklaburi District , Maeklong basin, Kanchanaburi Province, Thailand, 1 April 2004, A. Tejavej et al.

Paratypes. UNMF 00575 (10 specimens), 43.8–97 mm SL, same data as holotype . UNMF 00575 (11 specimens), 43.8–97 mm SL, Sangklaburi District , Maeklong basin, Kanchanaburi Province, Thailand, 1 April 2004, A. Tejavej et al . UNMF 0035 (7 specimens), 63–74.8 mm SL, Krung-Krai , Srisawat District, Maeklong basin, Kanchanaburi Province, Thailand, C. Grudpan et al . RLIKU 1372 (1 specimen), 88.5 mm SL, same locality ; 11 April 2003, N. Panitvong. THNHM.F.00531, (3 specimens) 37.1–78.5 mm SL, Huai Maelamung , Umpang District, Maeklong basin, Tak Province, Thailand, 24–26 July 2002, Y. Vilasri .

Other materials. THNHM UNCAT (5 specimens), 71.8–92.2 mm SL, Huai Mae La Mun , Dan Ta Chalab , Srisawat District, Kanchanaburi, Thailand, 20 July 1999, Tanya Chan-Arb . THNHM UNCAT (4 specimens), 54.2–69.1 mm SL, Huai Sai Khao at Klong Kor (Huai Kae Kaeng), Maeklong basin, Thailand, 16 January 1999, Tyson Roberts et al .

Diagnosis. A species of Barilius reaching approximately 100 mm SL that is distinguished from all congeners by the combination of a large, elongated blotch at the caudal-fin base (blotch is formed by the fusion of the large caudal spot at the fleshy end of the caudal base and the last vertical bar on the flank) that extends about 1/3 of the distance from the caudal-fin origin beyond the last scale on the caudal base to the margin of the caudal fork ( Fig. 2A); an anal-fin origin opposing the 2nd–4th branched dorsal-fin rays; eight scale rows above the lateral line; dark pigment on the dorsal fin concentrated mainly along the margins of the rays ( Fig. 3A); 36 or more precaudal lateral-line scales; small dentary tubercles; and, if present, a short, small pair of rostral barbels.

All other Southeast Asian species of Barilius except Barilius bernatziki ( Fig. 4A) and B. dogarsinghi ( Fig. 4B) have a small, or no caudal spot ( Fig. 2B). Barilius ornatus ( Fig. 5) has an anal-fin origin opposing or behind the 5th (rarely 4th) branched dorsal-fin ray and has a small, or no caudal spot. Barilius pulchellus has dark pigment on the dorsal fin concentrated mainly at the middle of the interradial membranes forming a blotch ( Fig. 3C), and large dentary tubercles even on nonbreeding specimens ( Fig. 6B). Barilius bernatziki , with a large caudal blotch, has 33 lateral-line scales or less. Barilius dogarsinghi has a highly conspicuous, deep vertical blotch at the base of the caudal fin that barely extends onto the caudal fin, as well as a strong, submarginal pigment band on the dorsal fin ( Fig. 4B), and long rostral and maxillary barbels that are generally equal to or more than 50% of the distance between the origin of the rostral barbels and the corner of the mouth.

Description. Morphometric and meristic measurements in Tables 1 & 2 are based on 31 specimens (37.1–96.65 mm SL). Body shape and coloration are shown in Figs. 1A–C.

Body fusiform, deep and compressed with ventral profile more convex than dorsal profile. Head deep and compressed, snout slightly blunt to acute. Caudal peduncle long and narrow near base of caudal fin. Mouth large, oblique, terminal, with maxilla length varying from vertical line through anterior margin of eye to vertical line through anterior margin of pupil. Lower jaw with no or slight notch, with corresponding emargination in the upper jaw; in some specimens, lower jaw projects beyond upper jaw. Two pairs of barbels (often missing on either side): rostral and maxillary barbels generally short and tiny, often only rudimentary, with rostral barbel length generally far shorter than 50% of distance between origin of rostral barbel and corner of mouth. Rostral barbel often in rostral groove. Eye large, but size generally decreases with body length, from diameter longer than snout in small specimens to slightly shorter than snout in large specimens. Infraorbital bones large. Presumed developed male ( Fig. 1C) with greatly enlarged chest.

Scales. 36–39 scales in lateral-line row to end of hypural plate (rarely 36), 1–3 more scales to base of caudal fin. Eight scale rows above lateral line (predorsal scale row not included); 2–3.5 rows below lateral line; 17–21 scales in predorsal row; 10–14 circumpeduncular scales. Axillary process at the anterior base of pectoral fin and axillary scale at the anterior base of pelvic fin well developed.

Fins. Dorsal fin in posterior half of body (not including caudal fin); origin far behind vertical through origin of pelvic fin; with 2–3 simple rays and 7–8 branched rays; straight to slightly concave in most specimens; convex with middle and posterior branched rays lengthened in presumed developed male, with posterior tip surpassing vertical through posterior base of anal fin. Anal-fin origin at vertical line through 2nd to 4th branched dorsal-fin rays. Anal fin with 2–3 simple rays and 9–11 branched rays; first 3–4 branched rays elongated, creating concave margin; straight margin in presumed developed male. Lower lobe of caudal fin longer than or equal to upper lobe. Pectoral fin large, with 12–13 rays; often reaching base of pelvic fin. Pelvic fin with 7–9 rays; origin far in front of dorsal-fin origin; tip not reaching origin of anal fin; posterior tip not reaching anterior origin of anal fin except in presumed developed male.

Tuberculation. In most specimens, small tubercles are restricted mainly to snout and dentary ( Fig. 6A). On one presumed developed male tubercles present on dentary, end of maxilla, snout, region in front of, above, and below eye, and branchiostegal rays; scattered small tubercles on dorsal surface of head; dentary tubercles generally in 5–6 rows, anterior rows larger than posterior ones; large tubercles on side of snout, end of maxilla, front of eye, top of eye, small area below eye, and branchiostegal region; smallest tubercles on snout and dorsum.

Coloration (Live and fresh specimens). Dorsum greenish to grayish, sides green to silver depending on light angle, belly silver in most specimens. Some individuals with yellowish to slightly reddish-orange belly, generally not including lower jaw region. Some individuals with yellowish lower jaw. Side with 6–9 blue or green vertical bars (not including last bar that often fuses with caudal spot); each bar generally 1–2 scales wide; generally, only bars in front of pelvic fin reach or cross lateral line. Bars often broken into double bars both vertically and horizontally; number of bars on opposite sides of body often unequal. Last bar generally aligns, and often fuses with caudal spot at fleshy end of caudal base, forming elongated greenish, dark blue, or black blotch, about 1–4 exposed scales high and 3–7 exposed scales long. Large caudal spot extends deeply onto anterior region of interradial membranes of caudal-fin, reaching about 1/3 distance between origin of caudal-fin rays beyond the last scale on caudal base to end of fork, or beyond, of caudal fin. All bars may become indistinct, depending on light reflection and mood of specimen. Anal fin clear to yellowish-orange. Caudal fin with dark margins on principal rays, outer parts of peripheral branched rays, and entire branched rays in middle of fin; caudal-fin membranes clear to yellowish, upper and lower area of anterior part of fin opaque-white. Combination of opaque-white base of caudal fin and greenish, dark blue or black elongated caudal blotch creates a highly conspicuous eye-like mark. Dorsal fin clear, light orange or pink, with dark pigment on rays and membranes; pigment concentrated along margins of dorsal-fin rays. Dark pigment on first 3–5 branched dorsal rays does not reach tip of fin in most specimens, leaving it clear to white, but in some individuals dark pigment expands into inter-membrane region of the dorsal fin, giving it a smoky appearance. In presumed developed male, dark pigment expands to the anterior tip of the dorsal fin. Coloration of presumed fully developed dominant male is not yet known.

Coloration (Preserved). Silvery, white, red, and green coloration usually disappears. Dorsum dark brown to dark gray; ventral areas lighter. All dark pigment in fins, body bars and caudal blotch turns dark brown to black. Dark, thin horizontal stripe occasionally appears midlaterally, from behind opercle to caudal base. Dark pigment of caudal blotch occasionally fades away, revealing last bar and caudal spot underneath.

Distribution. Barilius signicaudus is only known from the headwaters of the Khwae Yai Khwae Noi branches of the Maeklong River ( Fig. 7). It is has not been found in the headwaters of the Pachee and Phetchaburi rivers, which are also part of Maeklong basin ( Vidthayanon et al. 1997).

Habitat. Barilius signicaudus is found in mountainous areas, in fast-flowing streams and small rivers with clear water and gravel or cobble bottoms. Juveniles are found near shallow shorelines and behind large rocks where the flow is slower. Fishes that were found together with B. signicaudus at Sangklaburi included Barilius koratensis , Poropuntius melanogrammus , Mystacoleucus marginatus , Garra spp. , Rasbora cf. rasbora , Rasbora paucisqualis , Microdevario kubotai , Crossocheilus siamensis , Labiobarbus sp. , Acanthocobitis zonalternans , Schistura spp. , Nemacheilus pallidus , Botia morleti , Glyptothorax spp. , Batasio triginus , Xenenthodon sp. , Parambassis siamensis , Tetraodon sp.

Etymology. The specific epithet, signicaudus , a noun, is from the Latin signum, “flag or sign”, and cauda, “tail”.