Pseudeutropius indigens, Ng, Heok Hee & Vidthayanon, Chavalit, 2011

Ng, Heok Hee & Vidthayanon, Chavalit, 2011, Pseudeutropius indigens, a new species of schilbeid catfish (Teleostei: Siluriformes) from peninsular Thailand, Zootaxa 3037, pp. 45-50 : 46-48

Pseudeutropius indigens , new species

( Fig. 1 )

Pseudeutropius sp. 1— Vidthayanon, 2002: 77.

(?) Pseudeutropius cf. moolenburghae — Lheknim, 2004: 92.

Type material. Holotype: NIFI 3074, 67.1 mm SL; Thailand: Narathiwat Province, Toh Daeng peat swamp, Khlong Pak Pla, 6°11'11"N 102°1'32"E; C. Vidthayanon, 13 February 1998.

Paratypes: NIFI 4416 (13), 29.5–54.4 mm SL; UMMZ 249541 (7), 29.6–35.6 mm SL; data as for holotype.

Diagnosis. The new species is distinguished from P. moolenburghae in having fewer anal-fin rays (37–41 vs. 42–49), fewer rakers on the first gill arch (33–35 vs. 43–45) and a wider head (10.5–11.0% SL vs. 8.5–9.9); and from P. brachypopterus in having more anal-fin rays (37–41 vs. 31–35), and a shorter (23.1–24.3% SL vs. 27.0– 30.6) and narrower (10.5–11.0% SL vs. 11.7–14.0) head. It differs from P. mitchelli in having more anal-fin rays (37–41 vs. 35–37), and longer nasal, maxillary and mandibular barbels (reaching to at least anal-fin origin vs. not reaching beyond pelvic-fin base).

Description. Head depressed anteriorly, slightly compressed posteriorly. Snout acutely rounded in lateral view. Anterior naris located on anterior margin of snout; naris round, directed anteriorly. Posterior naris ovoid, subtended anterolaterally by nasal barbel. Dorsal surface of neurocranium covered with thin skin. Supraoccipital process relatively short, contacting anterior nuchal plate element. Eye ovoid, horizontal axis longest, ventrolaterally directed, located in middle third of head, visible in both dorsal and ventral view. Gill openings wide, extending from posttemporal to beyond isthmus.

Mouth terminal; upper and lower jaws of approximately equal length. Oral teeth small, viliform, in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band rounded, of equal width throughout. Dentary tooth band much narrower than premaxillary tooth band at symphysis, tapering laterally. Palatal (vomerine) teeth in elongate ovoid patch on either side of midline. Gill rakers on first gill arch 9+24=33 (2), 10+24=34* (1), 10+25=35 (1) or 11+24=35 (1). Branchiostegal rays 10 (10).

Barbels in four pairs. Maxillary barbel resting basally in shallow groove in skin, slender, extending to level of base of sixth or seventh anal-fin ray. Nasal barbel slender, extending to level of anal-fin origin. Inner mandibularbarbel origin close to midline; barbel thicker and longer than nasal barbel, extending to level of base of sixth or seventh anal-fin ray. Outer mandibular barbel originating posterolateral of inner mandibular barbel, extending to level of base of sixth or seventh anal-fin ray.

Body elongate, compressed. Dorsal profile almost evenly sloping from tip of snout to base of dorsal spine, with slight concavity at supraoccipital region; sloping gently ventrally from origin of dorsal fin to end of caudal peduncle. Ventral profile of body slightly convex to anal-fin base, then sloping slightly dorsally to end of caudal peduncle. Anterior chamber of swim bladder visible through large, thin-walled tympanic membrane. Skin smooth. Lateral line complete, with short, ventrally-directed accessory branches. Vertebral column with 12+29=41* (3) or 12+30=42 (7) vertebrae and 5–6 ribs.

Dorsal fin with spinelet, spine, and 5 (10) rays. Origin of dorsal fin at about two-fifths of body. Dorsal-fin margin convex, with anterior branch of fin rays longer than other branches. First soft dorsal-fin ray longest. Dorsal-fin spine straight, somewhat compressed, slender, posterior edge smooth in some individuals (including holotype), with 4–7 retrorse serrations in others. Anterior nuchal plate element narrow, elongate, pyriform.

Pectoral fin with slender, somewhat compressed spine, sharply pointed at tip, with 7,i (10) rays. Anterior margin of spine smooth in individuals above ca. 40 mm SL, with a series of asperities in middle third of spine in individuals below ca. 40 mm SL; posterior margin of spine with 7–18 retrorse serrations along entire length. Pectoralfin margin straight anteriorly, slightly convex posteriorly, imparting almost triangular appearance to fin.

Pelvic-fin origin posterior to vertical through posterior end of dorsal-fin base, with i,5 (10) rays and slightly convex margin; tip of adpressed fin slightly overlapping anal-fin origin. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin.

Adipose fin small, oar-like, with deeply-incised posterior portion, located above posterior third of anal-fin base. Adipose-fin base very short, spanning less than one fourteenth of SL.

Anal-fin origin located just anterior to level of middle of SL; anal-fin base long, about half of SL. Anal-fin margin slightly convex anteriorly, nearly straight posteriorly; with ii,35 (1), ii,36 (2), ii,37 (3), ii,38* (3) or ii,39 (1) fin rays, posterior rays shortest. Last ray free from caudal peduncle.

Caudal peduncle moderately deep. Caudal fin deeply forked, lobes pointed, symmetrical; outer principal rays about three-and-a-half times length of middle ray; fin with i,7,8,i (10) principal rays. Procurrent rays extend anterior to fin base.

Coloration. In 70% ethanol: Base color of head and body pale yellow, with melanophores arranged to form three indistinct longitudinal stripes on body running from immediately posterior to head to caudal flexure. First stripe on dorsum and dorsal quarter of body, second thinner, along lateral line; third originating ventral to tympanic membrane, running along base of anal fin. Posterior end of second stripe widening to form faint elongate, ovoid blotch on hypural region. Melanophores denser on dorsal surface of neurocranium, imparting dusky appearance there; scattered melanophores sometimes present on opercular region. Base of dorsal spine with denser aggregation of melanophores forming dark spot. All fins hyaline, devoid of markings.

Color in life. Opaque silvery body with white abdomen, yellowish and pigmented dorsally, dark spot at dorsalspine base, stripe and pigmented pattern same as preserved coloration above, fins hyaline.

Distribution. This species is known from the Toh Daeng peat swamp forest (within the Mae Nam Sungai Kolok drainage) in southern (peninsular) Thailand ( Fig. 2 ). It is also possibly present in river drainages northwards to the Isthmus of Kra as far north as the Tapi River.

Etymology. The specific epithet comes from the Latin meaning to need or want, in allusion to the lower number of anal-fin rays and gill rakers when compared to P. moolenburghae , the congener that it superficially resembles most.

Figures

FIGURE 1. Pseudeutropius indigens, NIFI 3074, holotype, 67.1 mm SL; Thailand: Narathiwat, Toh Daeng peat swamp.

FIGURE 2. Map showing distribution of Southeast Asian Pseudeutropius species. Solid symbols indicate records based on specimens examined, while open symbols indicate records from the literature.