Glyptothorax yuensis, Shangningam & Kosygin, 2022

Shangningam, Bungdon & Kosygin, Laishram, 2022, Glyptothorax yuensis, a new species of sisorid catfish (Teleostei: Sisoridae) from Myanmar, Zootaxa 5129 (1), pp. 118-128 : 119-121

Glyptothorax yuensis , new species

( Figs. 1–2 )

Type material. Holotype: ZSI FF 9015, 79.0 mm SL; Myanmar: Sagaing division, Tamu District, Yu River at Tamu , a tributary of Chindwin River , Chindwin-Irrawaddy drainage 24°13’37’’N 94°19’06’’E, Shangningam , 28 December 2018.

Paratypes: ZSI FF 9016–9017, 2, 61.3–87 mm SL; same data as holotype .

Diagnosis. Glyptothorax yuensis can be distinguished from all congeners in the Chindwin drainage in having the posterior insertion of the adipose fin is at a point two-thirds (vs. seven-eighths or more) along the entire length of the fin and in having (vs. lacking) anteromedial striae in the thoracic adhesive apparatus. Further, it is distinguished from all congeners in the Chindwin drainage except G. rugimentum and G. minutus in having a shorter adipose-fin base (7.6–10.0 % SL vs. 11.0–18.5). It differs from G. rugimentum in the absence (vs. presence) of light and dark vertical bands on the caudal peduncle and from G. minutus in having a shorter (vs. longer) nasal barbel not reaching (vs. reaching) anterior margin of the orbit. Details of differential diagnosis are provided in the discussion section.

Description. Morphometric data in Table 1 . Body slender. Head depressed with almost rounded snout when viewed dorsally and ventrally. Dorsal profile rising gently from tip of snout to dorsal-fin origin, then sloping gently towards end of caudal peduncle. Occipital process not in contact with anterior nuchal plate element. Anterior nuchal plate element visible as a saddle with arrow-shaped extensions when viewed dorsally. Ventral profile flat up to vent, slightly convex to end of anal-fin base, then decreasing gently towards caudal-fin base. Caudal peduncle elongate.

Eyes small, round, situated on dorsal surface of head. Mouth inferior, premaxillary tooth band partially exposed with mouth closed. Oral teeth small, villiform, in irregular rows on all tooth bearing surfaces. Barbels in four pairs. Maxillary barbel slender, extending middle of pectoral-fin base. Outer mandibular barbel longer than inner, almost reaching pectoral-fin base. Nasal barbel short, not extending to anterior margin of orbit when adpressed, extending halfway to orbital margin.

Thoracic adhesive apparatus present, longer than broad, consisting of ridges of striae in oval field extending from isthmus to level of middle of pectoral-fin base and with a conical-shaped median depression opening caudally ( Fig. 2 ). Anteromedial striae present. Striae oriented anterodistally, radiating from median depression. Ridges of apparatus not reaching gular region. Anus and urogenital openings located at vertical through posterior mid of adpressed pelvic fin. Lateral line complete, running mid-lateral. Vertebrae 20+18= 38. First branchial arch bearing 2+9 gill rakers.

Dorsal fin with i, 6 (3) rays; fin margin convex, located halfway between snout tip and adipose fin origin. Dorsal-fin spine strong, gently curved, with 5–6 serrae, longer than depth of body. Adipose fin shallow, acutely incised at the posterior extremity of its base with elongated posterior pointed tip (fig. 3). Pectoral fin with i,9 (2) or 10 rays; posterior fin margin almost straight. Pectoral spine very broad, covered with thick skin, its posterior margin with 12–13 serrae. Pelvic fin with i,5 (3) rays, its posterior margin slightly convex, surpasses the vent, tip of adpressed fin not reaching anal-fin origin. Anal fin with iv, 8 or 9 (2) rays, almost straight posterior margin. Caudal fin with 7+8 branched rays, strongly forked, with lower lobe slightly longer than upper lobe.

Coloration. In 70 % alcohol: dorsal and lateral surface of head and body light brown, ventral surface up to anal-fin origin yellowish. Two yellowish thin stripes on body: a mid-dorsal one, extending behind occipital process and another midlateral, originating at level of origin of pectoral fin, both stripes reaching caudal-fin base. Dorsal, pectoral, pelvic and anal-fins with dark-brown bases, margins yellowish. Adipose fin yellowish, its distal margin dark brown. Caudal fin white. Nasal, maxillary barbels brown. Mandibular barbel yellowish.

Distribution. The species is presently known only from the type locality, the Yu River, a tributary of Chindwin River, Sagaing Division, Myanmar ( Fig. 4 ).

Etymology. The species is named after its type locality, Yu River.

Figures

FIGURE 1. Glyptothorax yuensis, ZSI FF 9015, holotype, 79 mm SL; dorsal, lateral and ventral views.

FIGURE 2. Thoracic adhesive apparatus of Glyptothorax found in the Chindwin-Irrawaddy drainage. A, G. yuensis, ZSI FF 9015, 79 mm SL; B, G. burmanicus ZSI FF 8319, 116 mm SL; C, G. granulus ZSI FF 7581, 63 mm SL; D, G. igniculus ZSI FF 7088, 52.1 mm SL; E, G. ngapang ZSI FF 7087, 99 mm SL; F, G. senapatiensis ZSI FF 4971, 51.5 mm SL; G. G. trilineatus ZSI F 10380/1, 78.5 mm SL; H, G. ventrolineatus ZSI FF 7580, 69 mm SL. Figures not to scale.

FIGURE 4. Map showing type locality of Glyptothorax yuensis.