Zootaxa 3037: 45–50 (2011) www.mapress.com / zootaxa/ Copyright © 2011 · Magnolia Press ISSN 1175-5326 (print edition) Article ZOOTAXA ISSN 1175-5334 (online edition) Pseudeutropius indigens, a new species of schilbeid catfish (Teleostei: Siluriformes) from peninsular Thailand HEOK HEE NG1 & CHAVALIT VIDTHAYANON2 1 Tropical Marine Science Institute, National University of Singapore, 18 Kent Ridge Road, Singapore 119227. E-mail: heokhee@nus.edu.sg 2 Mekong River Commission, 184 Fa Ngum Road, Unit 18 Ban Sithan Neua, Vientiane 01000, Lao PDR. E-mail: chavalit@mrcmekong.org Abstract Pseudeutropius indigens, a new species of schilbeid catfish from peninsular Thailand, is described here. It can be distinguished from congeners in having the following combination of characters: head length 23.1–24.3% SL, head width 10.5– 11.0% SL, length of anal-fin base 45.6–50.4% SL, 37–41 anal-fin rays, isognathous jaws in which the premaxillary teeth are not visible when the mouth is closed, and long nasal, maxillary and mandibular barbels that reach to at least the analfin origin. Key words: Schilbeidae, Narathiwat, Malay Peninsula, Neotropius Introduction The schilbeid catfish genus Pseudeutropius currently consists of two species known from Sumatra and Borneo (P. brachypopterus and P. moolenburghae), and one species known from southern India (P. mitchelli). The genus remains poorly diagnosed, with the South Asian species currently assigned to Neotropius being morphologically very similar to Pseudeutropius species. The possibility thus exists that Pseudeutropius may not form a natural group in the absence of Neotropius (Ferraris, 2007). For some time, a population of Pseudeutropius morphologically similar to P. moolenburghae (a species known so far only from Sumatra) has been reported from peat-swamp habitats in southern (peninsular) Thailand (Vidthayanon, 2002). This population was suspected to belong to an unnamed species, and we present evidence in this study to confirm that this is indeed the case, describing it as Pseudeutropius indigens, new species. Material and methods Measurements were made point to point with dial calipers and data recorded to tenths of a millimeter. Counts and measurements were made on the left side of specimens whenever possible. Subunits of the head are presented as percentage proportions of head length (% HL). Head length and measurements of body parts are given as percentage proportions of standard length (% SL). Measurements follow Ng & Dodson (1999), and institutional abbreviations follow Ferraris (2007). Asterisks following a particular meristic count in the descriptive text refer to the condition in the holotype. Data for N. khavalchor was obtained from Kulkarni (1952), as we were unable to examine material representing this species. Accepted by R. Pethiyagoda: 26 Aug. 2011; published: 21 Sep. 2011 45 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. 46 · Zootaxa 3037 © 2011 Magnolia Press NG & VIDTHAYANON FIGURE 1. Pseudeutropius indigens, NIFI 3074, holotype, 67.1 mm SL; Thailand: Narathiwat, Toh Daeng peat swamp. 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. NEW PSEUDEUTROPIUS Zootaxa 3037 © 2011 Magnolia Press · 47 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. 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. Discussion The monophyly of Pseudeutropius has not yet been tested, and its composition is also subject to some debate. Members of the genus Neotropius, which are known from river drainages throughout the Indian subcontinent and Myanmar, have been assigned to Pseudeutropius by some authors (e.g. Shrestha, 2008) on account of their similar overall morphology. It is likely that both genera as currently understood do not represent natural groups (Ferraris, 2007), but a resolution of this problem requires additional work that is outside the scope of this study. The problem is compounded by the fact that Mo (1991) presented evidence to reassign Neotropius to the Bagridae, a hypothesis that requires rigorous testing. We have followed recent literature (e.g. Ferraris, 2007) in considering the two genera distinct, but highlight the need for attention to the problem here. There are three species of Neotropius currently recognized: N. acutirostris, N. atherinoides, and N. khavalchor. Pseudeutropius indigens differs from all three Neotropius species in having isognathous jaws in which the premaxillary teeth are not visible when the mouth is closed (vs. prognathous jaws in which the premaxillary teeth are visible when the mouth is closed) and longer nasal, maxillary and mandibular barbels (reaching to at least anal-fin origin vs. not reaching beyond pelvic-fin base). It further differs from N. acutirostris in having fewer anal-fin rays 48 · Zootaxa 3037 © 2011 Magnolia Press NG & VIDTHAYANON (37–41 vs. 42–48), from N. atherinoides in having a longer anal-fin base (45.6–50.4% SL vs. 39.3–40.8) and from N. khavalchor in having more anal-fin rays (37–41 vs. 24–36) and longitudinal dark stripes on the sides of the body (vs. stripes absent). Lheknim (2004) recorded Pseudeutropius cf. moolenburghae from the middle Tapi River drainage in southern Thailand (approximately 420 km northwest of the type locality of P. indigens). Although this record seems referable to P. indigens, there are more anal-fin rays reported for the material collected from the Tapi River drainage (40–43) than in P. indigens (37–41). We were unable to examine the material from the Tapi River to confirm its identity, and provisionally consider it as conspecific with P. indigens. TABLE 1. Biometric data for Pseudeutropius indigens (n=10). Holotype NIFI 3074 Range 67.1 29.6–67.1 Predorsal length 32.8 30.2–33.5 32.3±1.44 Preanal length 43.2 38.2–44.5 42.1±2.72 Prepelvic length 39.3 37.5–41.3 39.2±1.58 Prepectoral length 19.4 19.4–23.3 22.0±1.79 Length of dorsal-fin base 7.2 6.6–8.6 7.5±0.84 Length of dorsal spine 15.6 14.2–15.8 15.2±0.71 Length of anal-fin base 47.7 45.6–50.4 48.3±2.10 Pelvic-fin length 10.0 8.6–10.0 9.1±0.62 Pectoral-fin length 16.5 14.8–16.5 15.5±0.87 Pectoral spine length 14.5 12.0–15.0 13.5±1.52 Caudal-fin length 24.1 19.7–24.1 22.5±1.93 Length of adipose-fin base 6.9 6.4–6.9 6.7±0.21 Dorsal to adipose distance 43.8 39.9–43.8 41.5±1.68 Standard length (mm) Mean±SD %SL Post-adipose distance 18.9 17.3–18.9 18.3±0.69 Length of caudal peduncle 11.0 11.0–11.8 11.4±0.33 Depth of caudal peduncle 7.3 7.0–8.3 7.5±0.56 Body depth at anus 19.1 16.3–19.1 17.9±1.16 Head length 23.1 23.1–24.3 23.8±0.55 Head width 10.9 10.5–11.0 10.8±0.22 Head depth 14.0 14.0–14.3 14.2±0.13 %HL Snout length 28.4 28.4–32.2 30.4±1.69 Interorbital distance 34.8 26.4–34.8 30.4±3.58 Eye diameter 24.5 24.5–29.9 27.1±2.23 Nasal barbel length 196.8 140.6–196.8 173.0±23.55 Maxillary barbel length 181.9 181.9–216.1 199.3±17.11 Inner mandibular barbel length 245.8 192.2–245.8 222.1±23.74 Outer mandibular barbel length 235.5 192.2–239.1 225.6±22.33 NEW PSEUDEUTROPIUS Zootaxa 3037 © 2011 Magnolia Press · 49 Comparative material Neotropius acutirostris: ZRC 43482 (4), 68.3–77.6 mm SL; Myanmar: Yangon division, Win Paw Hta River. Additional data from Day (1877). N. atherinoides: ZMB 3013 (holotype), 83 mm SL; India: Tranquebar [=Tharangambadi, Tamil Nadu; photograph examined]. ZRC 49223 (3), 52.5–57.8 mm SL; India: West Bengal, Duttaphulia. Additional data from Hora (1941). Pseudeutropius brachypopterus: ZRC 53119 (62), 38.5–74.2 mm SL; Borneo: Kalimantan Tengah, Kecamatan Sebangau, Bereng Bengkel, access via track at 20 km along Palangkaraya–Banjarmasin road, 2°15'39.9"S 114°1'47.9"E. ZRC 38816 (1), 67.4 mm SL; Borneo: Kalimantan Barat, Kapuas River drainage, Sungai Bekuan near Bekuan. ZRC 38791 (4), 41.9–51.0 mm SL; Borneo: Kalimantan Barat, Kapuas River drainage, Danau Kandung Suli near Kampung Kandung Suli. ZRC 38605 (3), 48.4–51.1 mm SL; Sumatra: Jambi, Danau Rasau. ZRC 38634 (3), 58.9–66.6 mm SL; Sumatra: Jambi, Danau Arang Arang and Sungai Kembang. ZRC 41720 (20), 29.8– 63.9 mm SL; Sumatra: Jambi, Danau Arang Arang. ZRC 42362 (2), 60.0–63.0 mm SL; Sumatra: Jambi, Perlinghat, along main channel of Batang Hari River. P. mitchelli: BMNH 1863.12.18.134-135 (2 syntypes), 66–67 mm SL; India: Madras Presidency [photograph examined]. Additional data from Day (1877). P. moolenburghae: ZRC 41721 (1), 57.0 mm SL; ZRC 42330 (25), 41.5–46.2 mm SL; Sumatra: Jambi, Pijoan, Danau Saut Padang. Additional data from Roberts (1989). Acknowledgments We are grateful to Kelvin Lim (ZRC) for permission to examine material under his care and to an anonymous reviewer for constructively commenting on the manuscript. Literature cited Day, F. (1877) The fishes of India: being a natural history of the fishes known to inhabit the seas and freshwaters of India, Burma and Ceylon. Part iii. William Dawson & Sons, London, 369–552. Ferraris, C.J. (2007) Checklist of catfishes, recent and fossil (Osteichthyes, Siluriformes) and catalogue of siluriform primary types. Zootaxa, 1418, 1–628. Hora, S.L. (1941) Siluroid fishes of India, Burma and Ceylon. XI. Fishes of the schilbeid genera Silonopangasius Hora, Pseudeutropius Bleeker, Proeutropiichthys Hora and Ailia Gray. Records of the Indian Museum, 43, 97–112. Kulkarni, C.V. (1952) A new genus of schilbeid catfishes from the Deccan. Records of the Indian Museum, 49, 231–238. Lheknim, V. (2004) Annotated checklist of the fishes from the Tapi River basin, south Thailand. Natural History Journal of the Chulalongkorn University, 4, 83–98. Mo, T.-P. (1991) Anatomy, relationships and systematics of the Bagridae (Teleostei: Siluroidei) with a hypothesis of siluroid phylogeny. Theses Zoologicae, 17, 1–216. Ng, H.H. & Dodson, J.J. (1999) Morphological and genetic descriptions of a new species of catfish, Hemibagrus chrysops, from Sarawak, East Malaysia, with an assessment of phylogenetic relationships (Teleostei: Bagridae). The Raffles Bulletin of Zoology, 47, 45–57. Roberts, T.R. (1989) The freshwater fishes of western Borneo (Kalimantan Barat, Indonesia). Memoirs of the California Academy of Sciences, 14, 1–210. Shrestha, T.K. (2008) Ichthyology of Nepal. A study of fishes of the Himalayan waters. Himalayan Ecosphere, Kathmandu, 389 pp. Vidthayanon, C. (2002) Peat swamp fishes of Thailand. Office of Environmental Policy and Planning, Bangkok, 136 pp. 50 · Zootaxa 3037 © 2011 Magnolia Press View publication stats NG & VIDTHAYANON