Psilorhynchus khopai, Solo, Beihrosa & Lalronunga, Samuel, 2014

Solo, Beihrosa & Lalronunga, Samuel, 2014, Psilorhynchus khopai, a new fish species (Teleostei: Psilorhynchidae) from Mizoram, northeastern India, Zootaxa 3793 (2), pp. 265-272 : 266-270

Psilorhynchus khopai , new species

( Figs. 1 –2)

Type material. Holotype: PUCMF 13013, 63.2 mm SL; India: Mizoram: Tuisi River, a tributary of Kaladan River in the vicinity of Khopai village, Saiha District, 22°10'38"N, 93°02'45"E; Beihrosa Solo & Samuel Lalronunga, 16 November 2012.

Paratypes: PUCMF 13014 (6), 57.4–83.7 mm SL; PUCMF 13014/CS (2), 63.8–70.2 mm SL (cleared and stained); same data as holotype.

Diagnosis. Psilorhynchus khopai belongs to P. homaloptera species group and differs from its congeners in having the following combination of characters: mid-lateral body with 9–12 indistinct small dark brown round markings arranged in a longitudinal row, giving appearance of a faint brown lateral stripe; 7–9 unbranched pectoral fin rays; 3 unbranched dorsal and anal fin rays; 9 + 9 principal caudal fin rays; forked caudal fin; 14–17 predorsal scale rows; 39–41 lateral-line scale rows; adpressed anal fin tip not reaching caudal fin base; and, in life, a faint gold stripe along dorsal midline with 4–5 black spots between dorsal fin and caudal fin base.

Description. Biometric data are given in Table 1 . Head depressed; body small, compressed and elongate. Dorsal profile gently rising from tip of snout to origin of dorsal fin then sloping steeply towards caudal peduncle, body depth greatest at dorsal fin base. Ventral surface flattened from lower jaw to caudal fin base. Head wider than deep, eye ovoid, moderately large, not visible from ventral view, located middle of head length. Mouth inferior, snout rounded without transverse groove, ventral surface bordered by a longitudinal groove on each side. Tubercles minute, conical with pointed tips over entire surface of snout rostral cap, skin fold lateral to mouth, lateral and dorsal surface of head, along dorsal surface of unbranched and anteriormost branched pectoral fin rays, more prominent in males. Rostral cap and upper lip fused, separated by deep groove. Lower lip soft, not continuous with upper lip around corner of mouth. Lower jaw covered by thick squarish soft tissue layers (cushioned), papillated, continuous with skin of isthmus and connected with rostral cap by narrow strip of skin around corner of mouth.

Pre-epiphysial fontanelle moderate, rod-shaped, extending posteriorly middle of orbit. Post-epiphysial fontanelle similar in size and shape to pre-epiphyseal fontanelle, almost reaching posterior margin of orbit anteriorly. Five infraorbital bones (IO1-5); IO1-3 plate-like; IO1 biggest; IO4-5 greatly reduced in width. Gill membranes joined to isthmus. Fifth ceratobranchial with 4 rod or needle-like pharyngeal teeth, arranged in single row. Branchiostegal rays 3, all long and slender. Swim bladder coated by thick peritoneal membrane. Anterior chamber large, partially enclosed in bony cavity anteriorly by lateral process of the 2nd vertebral centrum and laterally by outer arm of os suspensorium; posterior chamber greatly reduced.

Dorsal fin with iii, 8 (9) rays. Anal fin with iii, 6 (9) rays. Principal caudal fin rays 9 + 9 (9), dorsal procurrent rays 6 (2), ventral procurrent rays 5 (2). Pelvic fin rays ii, 7 (9); pectoral fin rays vii, 9 (2) or viii, 9 (6) or ix, 9 (1). Pectoral fin horizontally placed, adpressed fin tip reaching two-third between pectoral fin origin and pelvic fin origin. Pelvic fin origin vertical through, or slightly posterior to, dorsal fin origin. Anus positioned between pelvic fins. Anal fin long, adpressed fin tip not reaching caudal fin base. Caudal fin forked, upper lobe slightly longer than lower lobe.

Scales cycloid and large, radii directed posteriorly. Lateral-line scale rows 39 (2) or 40 (5) or 41 (2), plus 1–2 on base of caudal-fin; transverse scale rows from dorsal fin origin to pelvic fin origin 3.5/1/2 (7) or 2.5 (2); scale rows around caudal peduncle 10 (9), arranged irregularly; pre-dorsal scale rows 14 (1), 15 (3), 16 (4) or 17 (1); scales between anus and anal fin origin 11(2) or 12 (7). Scales absent on mid-ventral region between pectoral fins. Belly region between pelvic and pectoral fin without scales. Vertebrae 40 (1) or 41 (1), consisting of 27 (1) or 28 (1) abdominal and 13 (2) caudal.

FIGURE. 2. Live individual of Psilorhynchus khopai . PUCMF 13014, 80.2 mm SL; India: Mizoram, Tuisi River.

Coloration. In 70% alcohol, body light brownish dorsally and light creamish ventrally. Brown stripe along dorsal midline from occiput to caudal fin base, most prominent from dorsal fin origin to caudal base. No dark spot on dorsal midline between occiput and dorsal fin origin. Mid-lateral body with 9–12 indistinct dark brown and round markings arranged in a longitudinal row and giving appearance of a faint brown lateral stripe; markings most prominent along posterior half of the body. Ventral surface of body without pigment. Anteriormost pectoral and pelvic fin rays with weak scattering of light brown melanophores along interradial membranes of unbranched rays. Dorsal fin without obvious pigmentation, but with a weak scattering of dark brown melanophores along interradial membranes. Anal fin with a faint interrupted bar across anterior half of fin, formed by a dense scattering of melanophores around last unbranched and three anteriormost branched rays. Caudal fin hyaline, formed by a dense scattering of melanophores along the surface of the principal rays; pigmentation most prominent along lower lobe. In life, body background colour light brown to grayish, a faint gold stripe along dorsal midline with 4–5 black spots between dorsal fin insertion and caudal fin base, Blotches along lateral body obscure, usually black in colour. Fin pigmentation most prominent in pectoral, pelvic, anal fin and along lower lobe of caudal fin. Dorsal fin hyaline.

Distribution and habitat. Known from the type locality, Tuisi River, a tributary of Kaladan River drainage ( Fig. 3 ). It is found in moderate- to fast-flowing portions of the river with sparse vegetation and a substrate of pebble, sand, gravel and small boulder ( Fig 4 ). Associated species captured with Psilorhynchus khopai include Glyptothorax spp., Garra spp., Schistura spp. and Batasio convexirostrum .

Etymology. Named after Khopai , a small village near the type locality. A noun in apposition.

Figures

FIGURE 1. Psilorhynchus khopai; a) holotype, PUCMF 13013, 63.2 mm SL; dorsal, lateral and ventral views; (b) paratype, PUCMF 13014, 68.7 mm SL, lateral view.

FIGURE 3. Map showing the collection locality of Psilorhynchus khopai (circle); n. b., a circle indicates more than a single locality.

FIGURE 4. Type locality of Psilorhynchus khopai (Tuisi River, Mizoram, India).

Tables

TABLE 1. Biometric data for Psilorhynchus khopai (n = 9). Ranges include values of holotype.

	holotype	range	mean	SD
Standard length	63.2	(57.4–83.7)
In % SL
Body depth	17.1	13.2–17.1	15.2	1.1
Head length	20.7	18.8–20.8	19.9	0.7
Pre-dorsal length	50.9	43.9–50.9	46.3	2.0
Pre-pectoral length	17.6	16.5–18.6	17.5	0.7
Pre-pelvic length	49.8	43.3–50.6	47.9	2.0
Pre-anal length	77.7	77.7–82.6	79.9	1.5
Distance from snout to anus	56.7	55.8–60.3	58.1	1.4
Distance from anus to anal fin	17.6	17.6–22.3	20.6	1.5
Caudal peduncle length	13.4	12.6–14.5	13.2	0.6
Caudal peduncle depth	8.4	6.8–8.6	7.7	0.6
Caudal peduncle width	4.0	3.3–4.7	3.9	0.5
Pectoral fin length	29.1	24.7–29.1	26.5	1.3
Pelvic fin length	20.9	19.2–22.3	20.9	0.9
Length of last unbranched anal ray	14.3	13.0–17.9	15.3	1.3
Length of last unbranched dorsal ray	23.7	20.1–24.4	22.8	1.4
In % HL
Head width	73.9	70.5–75.8	73.4	2.2
Head depth	42.0	39.8–43.4	41.6	1.3
Eye diameter	19.6	17.4–20.9	19.4	1.2
Snout length	55.1	52.7–55.3	54.3	1.1
Inter-orbital width	46.4	43.5–46.4	44.9	0.9
Mouth width	33.3	32.6–35.4	33.9	1.3