Glyptothorax pongoensis Tenali and Singh, 2024

Tenali, Diamond Rajakumar, Singh, Pratima, Pratap, Gudabandi Vijaya, Phom, Nyamkham, Ratnaraju, Maka & Kosygin, Laishram, 2024, Glyptothorax pongoensis, a new species of rheophilic catfish (Sisoridae) from the Brahmaputra River drainage, Nagaland, India, Journal of Natural History 58 (37 - 40), pp. 1377-1391 : 1378-1381

Glyptothorax pongoensis Tenali and Singh sp. n.

( Figures 1–2a )

Type material

Holotype. ZSI FF 9982, 72.8 mm standard length (SL); India: Nagaland: Longleng district: Yongmon River, Pongo Forest , ( Brahmaputra River drainage), 26.4633°N, 94.9022°E; Diamond Rajkumar Tenali , 23 November 2020.

Paratypes. ZSI FF 9983, 2, 64.5, 70.2 mm SL; collected with the holotype.

Diagnosis. Glyptothorax pongoensis is distinguished from its congeners from the Indian sub-continent by the following combination of characters: an ovate-shaped thoracic adhesive apparatus with skin ridges present over the entire apparatus, including the subulate-shaped depressed region, presence of plicae on the ventral surface of pectoral fin spine and first ray of pelvic fin. Further, it can be distinguished from its congeners by having a long head (23.3–26.3% SL), deep body (depth at anus 15.1–16.4% SL), W-shaped anterior nuchal plate element, dorsal-fin origin nearer to the snout tip than to the origin of adipose fin, posterior margin of dorsal spine rugose with 4–5 ridges, nasal barbel not reaching orbit when adpressed, and a body with two longitudinal pale-cream stripes, one each along mid-dorsal and lateral line.

Description. Morphometric data in Table 1 . Body elongate. Head depressed with rounded snout when viewed dorsally and ventrally. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gently from there to origin of adipose fin, then to end of caudal peduncle. Occipital process not in contact with anterior nuchal plate. Anterior nuchal plate saddle-like with W-shaped extensions when viewed dorsally ( Figure 3a ). Ventral profile flat up to posterior end of pectoral-fin base, then slightly convex to anterior margin of anal-fin origin, thereafter rising gently to end of caudal-fin base. Caudal peduncle deep. Mouth inferior, lips papillate. Eyes small, round, located on dorsal surface of head. Thoracic adhesive apparatus ovate leaf-shaped, longer than broad, not reaching gular region, extending from isthmus to slightly beyond posterior pectoral-fin base with poorly developed subulate-shaped median depression, narrowly opens by loosely packed dermal ridges posteriorly. Skin ridges present almost over entire apparatus, including depressed region ( Figure 2a ). Anus and urogenital opening located at vertical through anterior half of adpressed pelvic fin. Skin on head and body thickly tuberculated with rounded tubercles. Lateral line complete.

Barbels in four pairs. Maxillary barbel shorter than head, slender, almost reaching base of third branched pectoral ray. Outer mandibular barbel longer than inner, reaching gill opening. Inner mandibular short, half the length of outer mandibular barbell, reaching vertically anterior margin of orbit. Nasal barbel short, not reaching anterior margin of orbit when adpressed.

Dorsal fin with I, 6 rays, its origin nearer to snout tip than to adipose fin origin. Dorsal-fin spine strong, almost straight, rugose posteriorly with 4–5 ridges, and smaller than depth of body at its origin. Adipose fin short; with anterior margin slightly convex and posterior margin straight, acutely incised at the posterior extremity of its base. Pectoral fin with I, 10 rays; its posterior margin almost straight. Pectoral-fin spine broad, long; its anterior margin smooth, posterior margin with 10–11 serrae. Pelvic fin with I, 5 rays, its tip not reaching anal-fin origin when adpressed. Ventral surface of pectoral-fin spine and first pelvic-fin ray plaited. Anal fin long, with II, 10 or 11 rays; its origin slightly anterior to adipose-fin origin. Caudal fin deeply forked, with 7 + 8 branched rays. All the fins with numerous minute tubercles on fin rays.

Colouration. In 70% alcohol: Dorsal surface of the head and body greyish; lateral surface light brown fading to yellowish cream ventrally. The anterior nuchal plate is seen as a distinct pale W-shaped saddle when viewed dorsally. A faint pale mid-dorsal stripe is on the dorsal surface of the body, and a narrow mid-lateral stripe runs along the entire body length, originating from the occiput and superimposing on the lateral line. Base and distal third quarter of dorsal and anal fins with black bands. Adipose fin creamish yellow, with a broad black band in the middle. Pectoral and pelvic fins are dusky with a black base and hyaline distal margin. Caudal fin mottled with black spots with a broad W-shaped black spot on the base and hyaline tip.

Distribution. Glyptothorax pongoensis is known only from the type locality, the Yongmon River (Brahmaputra River drainage), Longleng District, Nagaland, India ( Figure 4 ).

Etymology. The species is named after its type locality, Pongo Forest, Nagaland, India.

Figures

Figure 1. Glyptothorax pongoensis, ZSI FF 9982, holotype, 72.8 mm SL: (a) dorsal; (b) lateral; (c) ventral views.

Figure 2. Thoracic adhesive apparatuses of: (a) Glyptothorax pongoensis, ZSI FF 9982, 72.8 mm SL; (b) G. mibangi, holotype, RGUMF 243, 79.0 mm SL;and (c) G. punyabratai, SISGPUN.1/NBFGR,paratype, 144.0 mm SL.

Figure 3. Dorsal view of nuchal plate elements of: (a) Glyptothorax pongoensis, ZSI FF 9982, 72.8 mm SL; (b) G. gopii, holotype, ZSI FF 5007, 63.5 mm SL;(c) G. heokheei, ZSI FF 9555, 152.0 mm SL; and (d) G. senapatiensis, ZSI FF 4971, 51.5 mm SL.

Figure 4. Map showing the type locality of Glyptothorax pongoensis.