Glyptothorax chakpiensis, Shangningam & Kosygin, 2024

Glyptothorax chakpiensis sp. nov.

( Figures 1A–C View Figure 1 , 2 View Figure 2 )

Type material: Holotype: 72.0 mm SL: India: Manipur: Chandel district: Chakpi River, headwaters of Chindwin drainage, 24˚08 N 94˚00 E; 28-xii-2018, Bungdon Shangningam (ZSI FF 8677).

Paratypes: 4 specimens, 61–77.0mm SL, same data as holotype (ZSI FF 8678); 1, 83.0 mm SL, same data as holotype (ZSI FF 10463) .

Diagnosis: Glyptothorax chakpiensis is distinguished from all congeners in the Chindwin drainage in having a slender body, its depth at dorsal-fin origin: 10.4–

13.1% SL and at anus: 11.2–12.0% SL. Further, it can be distinguished from congeners by the combination of the following characteristics: lanceolate-shaped thoracic adhesive apparatus, median depression almost enclosed posteriorly by skin ridges, its length 15.1–17.5% SL; a short nasal barbel not reaching the anterior margin of the eye; the first branchial arch with 2+9 rakers; body with two longitudinal yellowish stripes, and caudal fin with two triangular dark blotches at the anterior base.

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

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

Thoracic adhesive apparatus is lanceolate-shaped, longer than broad, extending from the isthmus to the posterior border of the pectoral-fin base, not reaching the gular region; its median depression is almost enclosed posteriorly by skin ridges ( Figure 2 View Figure 2 ). Anus and urogenital openings located at vertical through posterior mid of adpressed pelvic fin. The lateral line is complete, running mid-lateral. First branchial arch bearing 2+9 gill rakers. Vertebrae 24+19 =43.

Dorsal fin with i, 6 (6) rays; its margin convex, situated halfway between snout tip and origin of adipose fin.

Dorsal-fin spine is strongly curved gently with a slightly rough surface in the middle, greater than the depth of the body. Adipose fin short, anterior margin more or less straight, posterior margin convex with a slightly pointed tip. Pectoral fin with i, 9(2) or 10 (4) rays; posterior fin margin almost straight. The pectoral spine is very broad, and covered with thick skin, and its posterior margin with 9-13 serrae. Pelvic fin with i, 5 (6) rays, its posterior margin more or less convex, surpasses the vent, its tip not reaching anal-fin origin when adpressed. Anal fin with ii, 8 (6) rays, almost straight posterior margin. Caudal fin with 7+8 branched rays, deeply forked, with lower lobe slightly longer than upper lobe.

Colouration: In 70% alcohol, the dorsal and lateral surfaces of the head and body are light brown, while the ventral surface is yellowish up to the origin of the anal fin. The body features two yellowish stripes: one middorsal stripe that extends behind the occipital process and one mid-lateral stripe originating at the level of the pectoral fin, both reaching the base of the caudal fin. The dorsal, pectoral, pelvic, and anal fins have dark brown bases with yellowish margins. The adipose fin is yellowish with a dark brown distal margin. The caudal fin has two triangular dark blotches at its anterior base. The nasal and maxillary barbels are brown, while the mandibular barbels are yellowish.

Distribution: This species is currently known only from its type locality, the Dujang stream, a tributary of the Chakpi River in the Chindwin drainage of Manipur, northeast India. The habitat is characterized by cool, swiftly flowing water with a rocky bottom and numerous riffles.

Etymology: The species is named after the Chakpi River, the type locality.