Psilorhynchus chakpiensis, Shangningam, Bungdon & Vishwanath, Waikhom, 2013

Shangningam, Bungdon & Vishwanath, Waikhom, 2013, A new species of Psilorhynchus (Teleostei: Psilorhynchidae) from the Chindwin basin of Manipur, India, Zootaxa 3694 (4), pp. 381-390 : 383-387

Psilorhynchus chakpiensis , new species

( Fig. 1 )

Type material. Holotype: MUMF 12071, 53.1 mm SL; India: Manipur state, Chandel District, Chakpi River at Chakpikarong, 24°12'02.36''N 93°54'50.36''E; BD Shangningam, 14 Dec 2011.

Paratypes: MUMF 12072–76 (5), 45.7–48.5 mm SL; same data as holotype. Two paratypes (MUMF 12073– 76, 45.7–47.6 mm SL), dissected for osteology.

Diagnosis. A species of Psilorhynchus belonging to the P. balitora species group is distinguished from other members of the group by its longer caudal peduncle (17.8–20.5% SL vs. 8.9–15.2 in P. balitora , P. brachyrhynchus , P. breviminor , P. nepalensis , P. pavimentatus , P. gokkyi , P. piperatus , P. hamiltoni and P. rahmani ). Psilorhynchus chakpiensis is distinguished from P. amplicephalus by its smaller eye (24.5–29.2% HL vs. 32.4–36.0) and fewer lateral-line scales (30–31 vs. 32). Psilorhynchus chakpiensis further differs from P. breviminor , P. nepalensis , P. rahmani and P. pavimentatus in having a greater head depth (59.4–70.4% HL vs. 51.0– 55.8 in P. breviminor , 50.0– 56.8 in P. nepalensis , 53.3–59.2 in P. rahmani and 54.5–59.0 in P. pavimentatus ). Psilorhynchus chakpiensis is distinguished from all congeners in having a caudal-fin pattern consisting of two black bars, one incomplete bar near the base of the upper lobe, and a complete bar across the centre of the fin, traversing from the upper to the lower margin of the fin.

Description. Morphometric data are in Table 1 . Body high, greatest depth at dorsal-fin origin. Dorsal profile steeply rising from tip of snout to occiput and further arched to dorsal-fin origin, sloping gently towards caudal peduncle. Ventral profile straight, from lower jaw to caudal-fin base.

Head and eye large, snout rounded, mouth inferior. Entire surface of snout, lateral surface of head, rostral cap, cushion covering lower jaw, and papilliferous skin folds lateral to mouth covered with small conical tubercles with keratinised tips. Tubercles arranged as series of small, irregular longitudinal ridges on dorsal surface of head. Rostral cap and mouth separated from rest of head by deep longitudinal groove on each side ( Fig. 2 ). Rostral cap dome-shaped, fused with upper lip, separated by a shallow groove. Posterior one-third of rostral cap up to region bordering upper lip with horizontally arranged pointed tubercles. Upper lip with numerous unculi. Lower jaw covered by thick cushion, composed of two adnate tissue layers; anterior, deeper layer on lower lip, smooth, not continuous with upper lip around corner of mouth; posterior, superficial layer thick, continuous with skin of isthmus, papillate; 1–2 rows of prominent globular papillae behind upper lip. Superficial layer connected with rostral cap by narrow strip of skin, corner of mouth extended posterolaterally, broadened as a ridged; slightly papillated skin fold at posterior lateral-most corner of mouth.

Large pre-epiphysial fontanelle. Five infraorbital bones (IO1–5); IO1–3 platelike; IO4–5 reduced in width, composed of sensory canal ossification only. Gill membranes joined to isthmus. Fifth ceratobranchial with four needle-like pharyngeal teeth, arranged in single row. Branchiostegal rays 3, anteriormost ray greatly reduced in size ( Fig. 3 ). Anterior swim bladder chamber surrounded by thick peritoneal tunic and partially enclosed in bony capsule formed anteriorly by lateral process of 2nd vertebral centrum and laterally by outer arm of os suspensorium. Posterior swimbladder chamber greatly reduced in size.

Paired fins large, horizontally placed. Pectoral fin with v.10 rays ( Fig. 4 ), reaching vertical through dorsal-fin origin, reaching to 1–2 scale rows anterior to pelvic-fin origin when adpressed. Pelvic fin with ii.7 rays, located behind dorsal-fin origin, opposite to 3rd branched dorsal-fin ray. Skin on ventral surface of unbranched paired-fin rays thickened, covered with layer of unculi, forming adhesive pads. Dorsal fin with iii.9 rays, high, tip rounded, posterior edge concave. Anal fin with ii.6 rays, long, posterior edge concave, reaching caudal-fin base when adpressed. Caudal fin with 10+9 principal rays, 4(3) or 5(3) dorsal and 3(4) or 4(2) ventral procurrent rays, emarginated; upper lobe slightly longer than the lower.

Anus located 3 scale rows behind pelvic-fin origin. Scales large, 30 (2) or 31 (4) along lateral line, 2(3) or 3(3) on caudal-fin base. 3.5/1/2.5 (5) or 4/1/3 (1) transverse scale rows from dorsal- to pelvic-fin origin, 18 (4)–19 (2) circumferential scales, 10 around caudal peduncle, 10(1) or 11(5) predorsal scales, 6 (1) or 7 (5) scales between anus and anal-fin origin. Scales absent from ventral regions between pectoral fins. Total number of vertebrae 33, comprising 22 (1) or 23 (1) abdominal and 10 (1) or 11 (1) caudal vertebrae.

Coloration. In 10% formalin body background light cream. Occiput and dorsal surface of snout dark brown. Scales on flanks and dorsal surface edged with dark pigment. Scales bases with small melanophores, posterior edges hyaline. Dorsal surface between occiput and dorsal fin with two faint brown saddles. Four brown saddles along dorsal surface between dorsal-fin origin and caudal-fin base. First saddle between insertions of branched dorsal-fin rays 3–9, second saddle between dorsal- and anal-fin origin, above posterior end of pelvic fin, third saddle directly above anal-fin origin and fourth saddle situated anterior to caudal-fin base.

Flank with seven indistinct round to elongated dark brown blotches arranged in a longitudinal row. First extending from behind opercle to lateral-line scales 6–7, second on lateral-line scales 10–13, in region between occiput and middle of dorsal fin, third and fourth below first and second saddles, fifth below region between second and third saddles, sixth below third saddle and seventh below posterior-most saddle. Rows of black spots on fin rays. Dorsal-fin rays speckled with black melanophores basally and interrupted black band medially on branched rays. Anal fin immaculate. Caudal fin with a roughly Y-shaped black band, one oblique complete bar in middle extending from upper to lower margin, and a shorter incomplete bar on upper half, confluent with oblique bar in middle of fin. Peritoneal lining silvery, speckled with dark melanophores. In live, pigmented regions dark brown on light yellowish background.

Distribution and habitat. Psilorhynchus chakpiensis is known from the Chakpi River, Chindwin basin in Manipur, India ( Figs. 5 & 6 ). The type locality, Chakpi River, is cool, shaded and swiftly flowing with a gravel bottom, rocky bed substrate and numerous riffles. The species usually inhabits sandy substrate with pectoral fins spread horizontally while feeding at the bottom and adhering to rocks while at rest. Other species collected from the type locality includes species of Balitora , Channa, Garra, Glyptothorax, Mastacembelus, Neolissochilus, Schistura, and Tor .

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

Figures

FIGURE 1. Psilorhynchus chakpiensis, n. sp.: holotype. MUMF 12071, 53.1 mm SL; India: Manipur: Chindwin basin. a. lateral view; b. dorsal view; c. ventral view.

FIGURE 2. Mouth of: a. Psilorhynchus chakpiensis, MUMF 12071, 53.1 mm SL; b. P. amplicephalus MSUMNH 8, 48.2 mm SL; c. P. balitora MUMF 5058, 56.0 mm SL; d. P. nudithoracicus, MUMF 7045 66.0 mm SL; e. P. homaloptera MUMF 1001 / 1, 78.0 mm SL; f. P. microphthalmus MUMF 101, 48.7 mm SL. Scale bar = 1 mm.

FIGURE 3. Ventral view of hyoid bar and branchiostegal rays of Psilorhynchus chakpiensis paratype, MUMF 12073, 45.7 mm SL, anterior to left. Abbreviations: ACh, anterior ceratohyal; BR, branchiostegal rays; DHh, dorsal hypohyal; Ih, interhyal; PCh, posterior ceratohyal; VHh, ventral hypohyal. Scale bar = 1 mm.

FIGURE 4. Pectoral fin (ventral view) of Psilorhynchus chakpiensis, holotype, MUMF 12071, 53.1 mm SL.

FIGURE 5. Map showing collection locality of Psilorhynchus chakpiensis (Chakpi River).

FIGURE 6. Chakpi River, type locality and habitat of Psilorhynchus chakpiensis.

Tables

TABLE 1. Biometric data of holotype and paratypes of Psilorhynchus chakpiensis (n = 6).

Standard length (mm)	Holotype MUMF 12071 53.1	Range 45.7–53.1	Mean±SD
% of SL Body depth Head length	25.2 24.4	19.0–25.2 21.4–24.4	21.0±2.2 22.4±1.1
Pre-dorsal length Pre-pectoral length Pre-pelvic length	52.5 20.7 52.5	46.9–52.5 18.5–20.7 49.3–52.5	48.8±2.0 19.7±0.9 49.8±2.0
Pre-anal length Snout to anus length Anus to anal-fin length	83.2 116.0 19.3	77.1–83.8 96.0–116 16.0–20.8	80.0±2.9 102.3±7.4 18.5±1.6
Caudal-peduncle length Caudal-peduncle depth Pectoral-fin length	20.3 10.1 25.8	17.8–20.5 08.7–10.1 24.5–25.8	19.5±1.2 9.1±0.5 25.2±0.5
Pelvic-fin length Length of last unbranched anal-fin ray Length of last unbranched dorsal-fin ray	20.7 17.5 17.5	17.7–22.1 17.0–18.3 17.0–18.9	19.9±1.6 17.9±0.6 17.9±0.6
% of HL Head width Eye diameter	83.0 27.7	74.0–83.0 24.5–29.2	77.3±4.3 27.8±2.0
Snout length Interorbital width Mouth width	79.2 49.2 30.0	75.9–81.9 37.7–49.2 28.3–31.4	78.5±1.9 42.6±4.7 30.2±1.6