Pseudolaguvia virgulata, Ng, Heok Hee, 2010

Ng, Heok Hee, 2010, Pseudolaguvia virgulata, a new sisorid catfish (Teleostei: Sisoridae) from Mizoram, northeastern India, Zootaxa 2518, pp. 60-68 : 61-65

Pseudolaguvia virgulata sp. nov.

( Fig. 1 )

Type material. Holotype: PUCMF 1026, 24.2 mm SL; India: Mizoram, Sihthiang River, a tributary of the Teirei River in the vicinity of Sihthiang, 24°4'12.0"N 92°27'25.2"E; Lalramliana, 2 February 2010.

Paratypes: PUCMF 1027 (1), 28.8 mm SL; India: Mizoram, Bawrai River, a tributary of Langkaih River in the vicinity of Zawlnuam, 24°7'37.2"N 92°20'42.0"E; Lalramliana, 7 January 2010. PUCMF 1028 (1), 23.3 mm SL; India: Mizoram, Tlawng River at Sairang, 23°48'36.0"N 92°39'14.4"E; Lalramliana, 26 January 2010. PUCMF 1029 (2), 21.3–22.1 mm SL; UMMZ 248854 (2), 19.9–24.1 mm SL; India: Mizoram, Langkaih River in the vicinity of Zawlnuam, 24°10'19.2"N 92°20'42.0"E; Lalramliana, 8 January 2010.

Diagnosis. Pseudolaguvia virgulata differs from congeners in having a series of two to three pale, narrow longitudinal stripes running along the sides of a brown body; these lines extend from the middle of the dorsalfin base to the middle of the caudal peduncle (vs. absence of any longitudinal markings). The presence of a pale, Y-shaped marking on the dorsal surface of the head is also unique to this species. The presence of brown submarginal stripes running along the entire length of the caudal fin lobes (vs. transverse brown bands near the tips in other congeners) is otherwise only shared with P. inornata . Additional characters useful for diagnosing this species are outlined in the discussion.

Description. Biometric data as in Table 1 . Head depressed, body moderately compressed. Dorsal profile rising evenly from tip of snout to origin of dorsal fin, then sloping gently ventrally to end of caudal peduncle. Ventral profile flat to anal-fin base, then sloping gently dorsally to end of caudal peduncle. Supraoccipital spine not reaching nuchal shield. Weberian lamina well developed, approximately same length as supraoccipital spine, extending parallel to either side of spine. Eye ovoid, horizontal axis longest; located entirely in dorsal half of head. Orbit with free margin. Gill openings narrow, extending from posttemporal to isthmus. Branchiostegal membranes united at isthmus. Caudal peduncle of moderate length and depth. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin. Skin prominently tuberculate, with conical tubercles particularly prominent on dorsal third of head and body. Lateral line complete, midlateral. Vertebrae 10+19=29* (1), 10+20=30 (1), 11+19=30 (4), or 12+18=30 (1). Thoracic region with adhesive apparatus consisting of longitudinal, unculiferous ridges arranged in elliptical field and with prominent central median depression ( Fig. 2 ). Adhesive apparatus extending to two-thirds of distance between base of last pectoral-fin ray and pelvic-fin origin.

Mouth small, inferior, with papillate lips; upper jaw projecting beyond lower jaw. Oral teeth small, in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band consisting of single broad lunate patch across midline; with conical teeth, not exposed with mouth closed. Dentary tooth band narrow, with conical teeth.

Barbels in four pairs. Nasal barbel very short, broad, extending to one-third distance between its base and anterior orbital margin. Maxillary barbel slender, with broad skin flap at base, extending to two-thirds of distance between its base and base of pectoral-fin spine. Outer mandibular barbel with broad skin flap on dorsal margin, extending to base of pectoral-fin spine; inner mandibular barbel broad, shorter, reaching to vertical through posterior orbital margin.

Dorsal fin located about two-fifths along body, with 4,i (5) or 5* (2) rays, its margin straight. Dorsal-fin spine flattened, straight, robust; spine extending to line through middle of pelvic fin. Anterior margin of spine with 9–17 small, distinct serrations; posterior margin with 3–5 larger, indistinct serrations.

Pectoral fin with stout, blade-like spine, sharply pointed at tip, with 5,i (3) or 6,i* (4) rays. Anterior spine margin with 11–17 small, distinct serrations. Posterior spine margin with 6–8 large, very distinct serrae. Anterior and posterior pectoral-fin margin straight. Coracoid with moderately long posterior process, extending along proximal two-thirds of pectoral spine. Pelvic-fin origin at vertical through middle of dorsalfin base. Pelvic fin with i,5 (7) rays, its margin straight; tip of adpressed fin not reaching anal-fin origin. Adipose fin short, posterior end deeply incised, located above anal-fin base. Anal fin with iii,6 (1), iv,6,i (4) or iv,7* (2) rays, its anterior and posterior margins straight. Caudal peduncle moderately deep. Caudal fin deeply forked, with i,7,7,i (7) principal rays; upper and lower lobes pointed; both lobes of equal length, lower lobe slightly broader than upper. Procurrent rays symmetrical, extending only slightly anterior to fin base.

Coloration. In 70% alcohol: dorsal and lateral surfaces of head and body medium brown, fading to light brown on ventral surfaces of head and body. Two short, pale (light brown) lines on dorsal surface of neurocranium running from tip of snout to above orbits (through lateral ethmoids and anterior half of frontals), coalescing at posterior end of frontals, extending throughout supraoccipital to tip of process and continuing along nuchal shield to form a Y-shaped marking. Flanks with two or three pale (light brown), narrow longitudinal stripes, extending from vertical through middle of dorsal-fn base to middle of caudal peduncle. Dorsal fin brown, with irregular hyaline margin distally. Pectoral fin with irregular brown stripe running along its entire length. Pelvic fin with brown spot at base and smaller brown spots in middle of fin. Anal fin hyaline, with brown along base and irregular brown markings on fin. Caudal fin hyaline, with subdistal brown stripe running along length of each lobe. Nasal and maxillary barbels brown dorsally, light brown ventrally; all mandibular barbels light brown. Some specimens, when freshly preserved, with strong yellow tint ( Fig. 3 ).

Distribution and habitat. Known from the Barak River drainage in Mizoram, India ( Fig. 4 ). The Barak River forms the headwaters of the Surma-Meghna River system (one of the three river systems that combine to form the Ganges Delta). Pseudolaguvia virgulata has been collected from clear, shallow, moderately fastflowing streams with a predominantly sandy bottom.

Etymology. The specific epithet comes from the Latin adjective virgulatus, meaning striped, in reference to the narrow, pale longitudinal stripes on the flanks, which is diagnostic for this species.

Figures

FIGURE 1. Pseudolaguvia virgulata, PUCMF 1026, holotype, 24.2 mm SL; dorsal, lateral and ventral views.

FIGURE 2. Pseudolaguvia virgulata, PUCMF 1027, paratype, 28.8 mm SL. Ventral view showing details of thoracic adhesive apparatus.

FIGURE 3. Pseudolaguvia virgulata, PUCMF 1027, paratype, 28.8 mm SL, showing yellowish tinge in some freshly preserved specimens.

FIGURE 4. Map showing collection localities of Pseudolaguvia virgulata. Each circle may represent more than one locality.

Tables

TABLE 1. Biometric data for Pseudolaguvia virgulata (n = 7)

	Holotype	Range	Mean±SD
%SL
Predorsal length	42.1	39.6–42.9	41.1±1.42
Preanal length	64.5	64.5–66.7	65.8±0.98
Prepelvic length	47.9	47.9–50.6	49.9±1.31
Prepectoral length	23.6	21.9–24.9	23.7±1.33
Length of dorsal-fin base	19.8	17.2–19.8	18.1±1.15
Dorsal-fin spine length	22.3	21.5–24.0	22.8±1.08
Length of anal-fin base	16.5	14.6–16.5	15.3±0.83
Pelvic-fin length	14.9	14.6–16.2	15.4±0.77
Pectoral-fin length	28.5	28.1–28.8	28.5±0.29
Pectoral-fin spine length	24.4	23.6–26.2	25.0±1.19
Caudal-fin length	29.3	28.8–30.0	29.3±0.53
Length of adipose-fin base	13.6	12.9–15.0	13.7±0.93
Dorsal to adipose distance	16.1	14.5–17.0	15.9±1.03
Post-adipose distance	18.2	17.6–18.7	18.2±0.45
Caudal peduncle length	18.2	18.2–20.2	19.3±0.88
Caudal peduncle depth	8.7	7.8–9.7	8.6±0.82
Body depth at anus	14.5	14.5–17.4	15.5±1.37
Head length	29.3	28.8–32.2	30.3±1.53
Head width	24.4	21.2–24.4	22.7±1.33
Head depth	18.2	16.6–19.4	18.4±1.30
%HL
Snout length	54.9	48.0–54.9	51.5±3.07
Interorbital distance	35.2	29.3–35.2	33.6±2.89
Eye diameter	12.7	12.0–14.9	12.9±1.37
Nasal barbel length	18.3	10.8–18.3	13.6±3.30
Maxillary barbel length	74.6	60.0–74.6	66.8±5.99
Inner mandibular barbel length	38.0	32.0–38.6	36.6±3.09
Outer mandibular barbel length	62.0	47.7–67.5	60.2±8.63