Hemibagrus capitulum ( Popta, 1904 )

Ng, Heok Hee & Kottelat, Maurice, 2013, Revision Of The Asian Catfish Genus Hemibagrus Bleeker, 1862 (Teleostei: Siluriformes: Bagridae), Raffles Bulletin of Zoology 61 (1), pp. 205-291 : 234-237

Hemibagrus capitulum ( Popta, 1904)

( Fig. 23 )

Macrones fortis var. capitulum Popta, 1904: 186 (type locality: Bo River, central Borneo); 1906: 48, Pl. 3 Fig. 9 .

Bagrus nemurus (non Valenciennes, in Cuvier & Valenciennes, 1840) - Bleeker, 1851d: 416, 420; 1852a: 413; 1852b: 445; 1853a: 718, 722; 1853b: 181; 1854a: 428, 429, 432; 1854b: 65; 1855d: 393, 394; 1856a: 417, 419; 1856b: 4, 9; 1857a: 25; 1858d: 266; 1858e: 150 (in part); 1858f: 7; 1858g: 4; 1859d: 434; 1859e: 370; 1859g: 134 (in part); 1860a: 46; 1860b: 18.

Hemibagrus nemurus (non Valenciennes, in Cuvier & Valenciennes, 1840) - Bleeker, 1862: 55, Pl. 69 (in part); 1863a: 73; Hubrecht, 1887: 11; Fowler, 1905: 469; Mo, 1991: 132; Kottelat & Lim, 1995: 238; Ng & Tan, 1999: 357; Parenti & Downing Meisner, 2003: 45; Parenti & Lim, 2005: 189; Atack, 2006: 64; Ferraris, 2007: 90 (in part); Rahim et al., 2009: 11; Shah et al., 2009: 64; Ambak et al., 2010: 78; Jimmy et al., 2010: 56; Kamaruddin et al., 2011: 92; Hashim & Shah et al., 2012: 28; Rainboth et al., 2012: Plate 45, Fig. 944.

Macrones nemurus (non Valenciennes, in Cuvier & Valenciennes, 1840) - Günther, 1864: 80 (in part); Vinciguerra, 1880: 169; Boulenger, 1890: 38; Weber, 1894: 420 (in part); Vaillant, 1902: 54 (in part); Volz, 1904: 468; 1907: 166; Weber & de Beaufort, 1912: 536; 1913: 341 (in part); Rendahl, 1922: 201; Vinciguerra, 1926: 608; Hardenberg, 1931: 117; 1934: 306; 1935: 234; 1936: 234; Tweedie, 1936: 19.

Macrones (Hemibagrus) nemurus (non Valenciennes, in Cuvier & Valenciennes, 1840) - Steindachner, 1901: 446.

Macrones bleekeri Volz, 1903: 556 (type locality: Banjuasin, Palembang, Sumatra); 1904: 468 [primary junior homonym of Macrones bleekeri Day, 1877 ]; 1907:167.

Macrones planiceps (non Valenciennes in Cuvier & Valenciennes, 1840) - Tweedie, 1936: 19.

Macrones baramensis (non Regan, 1906) - Hardenberg, 1936: 234.

Mystus nemurus (non Valenciennes, in Cuvier & Valenciennes, 1840) - Herre & Myers, 1937: 69; Hora & Gupta, 1941: 26; Suvatti, 1950: 297 (in part); Inger, 1955: 65; Alfred, 1961: 36; Inger & Chin, 1962: 138, Fig. 69; Mohsin et al., 1977: 76; Mizuno & Furtado, 1982: 323; Mohsin & Ambak, 1982: 104, Fig. 4 ; 1983: 129, Fig. 95; Watson & Balon, 1984: 933 (in part); Zakaria-Ismail, 1984: 25; 1987: 408; 1993: 207, Pl. 5d; Roberts, 1989: 121; 1993a: 28, Fig. 63; Christensen, 1992: 600; Kottelat et al., 1992: 10; 1993: 66 (in part), Pl. 31; Ng et al., 1992: 18, Fig. 61; 1994: 209; Lim et al., 1993: 6; Kottelat, 1994: 412; Zakaria-Ismail & Lim, 1995: 322, Pl. 4b; Jayaram & Sanyal, 2003: 85, Fig. 17 ; Nyanti et al., 2006: 105; Shah et al., 2006: 56.

Mystus baramensis (non Regan, 1906) - Herre & Myers, 1937: 68; Suvatti, 1950: 295; 1981: 90; Mohsin et al., 1977: 76; Mohsin & Ambak, 1982: 106, Fig. 6 ; 1983: 130, Fig. 97; Jayaram & Sanyal, 2003: 39, Fig. 3 .

Aoria nemurus (non Valenciennes, in Cuvier & Valenciennes, 1840) - de Beaufort, 1939: 190.

Mystus johorensis Herre, 1940: 13 , Pls. 7–8 (type locality: Sungai Kayu , 16 miles north of Kota Tinggi, Johor, Peninsular Malaysia).

Mystus pahangensis Herre, 1940: 14 , Pl. 9 (type locality: Sungai Garam near Karak, Pahang, Peninsular Malaysia).

Macrones wycki (non Bleeker, 1858) - Tweedie, 1940: 70.

Mystus planiceps (non Valenciennes in Cuvier & Valenciennes, 1840) - Hora & Gupta, 1941: 27 (in part); Nyanti et al., 2006: 105.

Mystus (Mystus) johorensis - Jayaram, 1966: 446.

Mystus (Mystus) nemurus - Jayaram, 1966: 446 (in part).

Mystus (Mystus) pahangensis - Jayaram, 1966: 446.

Mystus sp. - Imaki et al., 1981: 41, Fig. 82.

Mystus cf. planiceps - Cramphorn, 1983: 19.

Hemibagrus chrysops Ng & Dodson, 1999: 48 (type locality: Serian

market, from Sadong River, Sarawak, Borneo); Parenti & Lim,

2005: 189; Ferraris, 2007: 87; Ng & Lim, 2008: 27, Fig. 21 . Hemibagrus aff. nemurus - Tan & Ng, 2000: 271. Hemibagrus cf. nemurus - Kottelat & Widjanarti, 2005: 159;

Rachmatika et al., 2005: 27. Hemibagrus fortis - Ferraris, 2007: 88 (in part). Hemibagrus johorensis - Ferraris, 2007: 89. Hemibagrus baramensis (non Regan, 1906) - Rahim et al., 2009:

11. Hemibagrus planiceps (non Valenciennes in Cuvier & Valenciennes,

1840) - Ambak et al., 2010: 78.

Material examined. — SUMATRA: Sumatera Utara: ZMA 121.626 , 2 ex., 146.2–191.3 mm SL ; ZMA 121.817 , 1 ex., 168.1 mm SL, Medan .

SUMATRA: Riau: ZRC 39032, 7 ex., 122.6–227 mm SL, Sungai Bengkwan, tributary of Indragiri (Batang Kuantan), 4 hrs downstream from Rengat ;

SUMATRA: Jambi: CMK 11221, 2 ex., 89.6–113.8 mm SL; ZRC 38663, 1 ex., 113.9 mm SL, Batang Hari near Tanjung Johor; ZMA 121.810 , 10 ex., 130.0–296.0 mm SL, Batang Hari at Jambi; ZRC 29516–29531 , 16 ex., 204.0– 380 mm , Jambi; ZRC 38975, 4 ex., 136.6–206.0 mm SL; ZRC 40534, 3 ex., 230.8–247.9 mm SL; ZRC 42554, 17 ex., 33.5–70.0 mm SL, Pasar Angso Duo (fish market) , Jambi; ZRC 39073, 2 ex., 62.4–71.3 mm SL; ZRC 39151, 1 ex., 115.2 mm SL, Berbak Nature Reserve, Sungai Air Hitam Dalam; ZRC 39181, 1 ex., 132.4 mm SL, Sungai Alai at 19.5 km Muara Bungo – Muara Tebo road; ZRC 42261, 10 ex., 71.7–123.2 mm SL, approx. 15 min after Kampung Rantau Panjang along Batang Hari confluence .

SUMATRA: Sumatera Selatan: NMBE 1020756 , 1 ex., 129.1 mm SL, brackish water at Banjuasin [holotype of Macrones bleekeri Volz ] ; UMMZ 155720 , 1 ex., 276.9 mm SL ; ZMA 121.816 , 2 ex., 147.4–156.8 mm SL, Palembang ; FMNH 15749 , 1 ex., 210.5 mm SL, Ogan River ; NRM 24986, 1 ex., 319.7 mm SL, Pladju fish market, 5 km downstream from Palembang ;; ZMA 121.815 , 1 ex., 74.6 mm SL, Biliton Island ;

MALAY PENINSULA: CAS 130991 , 1 ex., 100.7 mm SL, Thailand: Songkhla ; CAS 66346, 1 ex., 179.1 mm SL, Kelantan: Sungai Semukat, a tributary of Sungai Galas ; CMK 8198 , 1 ex., 84.6 mm SL, Terengganu: tributary of Sungai Terengganu immediately downriver of Sekayu Waterfall Park , 4°57'50.6"N 102°57'45.5"E ; CAS 130997 , 2 ex., 97.6–141.4 mm SL, Perak: Bukit Merah ; FMNH 47045 , 1 ex., 92.9 mm SL , FMNH 47320 , 1 ex., 107.6 mm SL, Perak: Krian, Bukit Merah ; CAS 132717 , 2 ex., 215.1–228.3 mm SL, Perak: Chenderoh Dam ; CAS 130999 , 2 ex., 76.1–85.1 mm SL, Perak: Telok Intan ; ZRC 41150, 9 ex., 159.6–269.5 mm SL, Perak: Sungai Perak at Kampung Kenderong, 3 km from Gerik , 5°24'52.5"N 101°9'5.1"E ; CAS 132716 , 3 ex., 82.9–144.6 mm SL, Kuala Lumpur ; ZRC 14899, 1 ex., 153.7 mm SL, Selangor: North Selangor Peat Swamp Forest , irrigation canal on W boundary ; ZRC 21483, 1 ex., 167.0 mm SL, Pahang: Rompin, Sungai Kinchin ; CAS 133025 , 1 ex., 192.2 mm SL, Pahang: Sungai Garam near Karak [holotype of H. pahangensis ] ; CAS 130990 , 2 ex., 51.9–58.4 mm SL , CAS 130996 , 2 ex., 66.6–95.1 mm SL, Malacca: Tasik Chin Chin ; USNM 101259 , 1 ex., 56.5 mm SL, Malacca: Jasin, outlet of Tasek Chin Chin ; CAS 133026 , 1 ex., 213.1 mm SL, Johor: Sungai Kayu, 26 km north of Kota Tinggi [holotype of H. johorensis ] ; CAS 130989 , 1 ex., 106.2 mm SL , CAS 131000 , 1 ex., 112.5 mm SL, Johor: Ayer Hitam ; CAS 131001 , 1 ex., 144.8 mm SL, Singapore ; CAS 132718 , 1 ex., 140.5 mm SL, Johor , 8 km N of Kota Tinggi ; CAS 132721 , 1 ex., 199.7 mm SL, Johor: Sungai Kayu ; FMNH 62314 , 4 ex., 35.6–56.4 mm SL, Johor: small stream along road from Kota Tinggi to Mawai ; USNM 229267 , 2 ex., 29.0– 30.4 mm SL, Johor: small tributaries of Sungai Sedili Besar, 10–23 km N of Kota Tinggi (on road to Mersing ) ; ZRC 2439 , 1 ex., 107.0 mm SL, Pahang: Kuala Tahan ; ZRC 3053 , 1 ex., 139.0 mm SL, Pahang: Tasek Bera ; ZRC 9555 , 1 ex., 128.7 mm SL, Johor: Mawai district ; ZRC 11642, 1 ex., 190.0 mm SL, Johor, near Layang-Layang .

BORNEO: Brunei: USNM 323366 , 1 ex., 46.6 mm SL, Labi, Wasah Rampayoh, off Labi road; USNM 328061 , 25 ex., 34.8–111.0 mm SL, Sungai Pang , tributary of Sungai Belait , downstream from Kampung Sukang; USNM 328089 , 17 ex., 16.8–99.0 mm SL, Saungai Arang, tributary stream of Ulu Belait , downstream from Sungai Tempine and Sungai Jagit; USNM 328114 , 2 ex., 123.8–147.2 mm SL, Sungai Buru, tributary stream of Sungai Belait , upstream from Kampung Melilas; USNM 328118 , 3 ex., 149.1–158.5 mm SL, Kuala Topi, confluence of Ulu Topi and Ulu Belait ; USNM 331812 , 1 ex., 176.6 mm SL, Ulu Ingei , upstream from base camp ; ZRC 40482, 11 ex., 67.8–245.3 mm SL, Sungai Merimbun, outlet from Tasek Merimbun into Sungai Tutong .

BORNEO: Sarawak: ANSP 152378 , 1 ex., 237.7 mm SL, Baram ; BMNH 1978.9 .5.49, 1 ex., 112.6 mm SL, Sungai Melinau ; BMNH 1983.6.20.19–20, 3 ex., 139.7–169.3, Batang Ai ; CAS 79353, 10 ex., 36.3–109.2 mm SL , USNM 325408 , 18 ex., 31.4–124.3 mm SL, Baleh River , creek entering southern bank approximately 20 km E of Sut River ; CAS 79354, 10 ex., 46.6–175.2 mm SL , USNM 325324 , 52 ex., 32.4–176.6 mm SL, Batang Balui , tributary stream, Long Saan ; CAS 79564, 67 ex., 26.5–230.7 mm SL, Fourth division, Baram drainage, Sungai Liam about 500 m above stream mouth, 3°19'26"N 114°45'19"E ; FMNH 63009 , 9 ex., 71.8–97.6 mm SL, Fourth division, Niah, Niah River at Pk. Lobang ; FMNH 68058 , 9 ex., 15.6–173.3 mm SL, Third division, Baleh River, Sungai Putai camp ; FMNH 68081 , 8 ex., 44.6–102.1 mm SL, Third division, tributary of Baleh River between Sungai Entunau and Sungai Putai ; FMNH 68566 , 1 ex., 105.2 mm SL, Fourth division, lower Niah ; FMNH 103620 , 10 ex., 54.0– 157.7 mm SL, Batang Balui , tributary stream, Long Ulu ; MCZ 100891 , 29 ex., 74.9–157.4 mm SL, Fourth division, Baram River drainage, Sungai Liting, about 4100 m above stream mouth ; NRM 27316, 40 ex., 20.1–224.9 mm SL, Fourth division, Baram River drainage, Sungai Kaha about 200 m from mouth, 3°23'N 114°34'E ; USNM 35730 , 4 ex., 132.2–188.3 mm SL ; USNM 35731 , 1 ex., 253.0 mm SL, Sadong ; ZRC 38753, 4 ex., 131.2–196.5 mm SL, Balai Ringin , stalls by roadside next to bridge over Sungai Kerang ; ZMA 114.396 , 3 ex., 133.7–201.6 mm SL ; ZRC 40498, 7 ex., 153.0– 232.5 mm SL, Miri , Kampung Bakung from Sungai Bakung turnoff after km 62 to Batu Niah ; ZRC 42653, 209.7 mm SL [holotype of Hemibagrus chrysops ] ; ZRC 40489 1 ex., 156.0 mm SL, Serian wet market, from Sadong River [paratype of Hemibagrus chrysops ] ,; ZRC 23008–23014 , 7 ex., 172.0– 210.7 mm SL, Rajang River at Sibu [paratypes of Hemibagrus chrysops ] ; ZRC 39518, 18 ex., 93.2–171.0 mm SL, Serian , market near Sungai Gadong [paratypes of Hemibagrus chrysops ] ; ZRC 39526, 5 ex., 198.2–219.8 mm SL ; ZRC 39747, 2 ex., 135.4–146.0 mm SL ; ZRC 40488, 7 ex., 131.4–212.7 mm SL, Serian market, from Sungai Kerang ; ZRC 39527, 3 ex., 210.3–220.8 mm SL ; ZRC 41860, 3 ex., 97.4–162.0 mm SL, Balai Ringin , stalls by roadside next to bridge over Sungai Kerang .

BORNEO: Kalimantan Barat: CAS 49378, 1 ex., 20.0 mm SL, Kapuas drainage, Sungai Engkayas , where it flows into right side of Kapuas mainstream about 2 km upstream from Sanggau ; CAS 49379, 2 ex., 149.0–167.0 mm SL, Kapuas drainage, Sungai Tekam, small forest stream where it enters right side of Kapuas main stream approx. 5–6 km upstream from Sanggau ; CAS 49380, 5 ex., 36.7–56.0 mm SL, Kapuas drainage, Sungai Tamang , small forested stream with rocky bottom flowing into Sungai Pinoh opposite mouth of Sungai Kelawai ; FMNH 94391 , 1 ex., 85.6 mm SL, several small forest streams where they flow into Kapuas mainstream within 10 km upstream from Sanggau ; CMK 10157, 1 ex., 140.6 mm SL, Kapuas River drainage, Sungai Sebadin, 0°50'22"N 111°57'12"E ; CMK 10444, 1 ex., 119.9 mm SL, Kapuas River at Nanga Piasa, 0°39'18"N 112°13'46"E ; CMK 10577, 3 ex., 63.5–137.4 mm SL, Kapuas River drainage: Sungai Melawi drainage, Sungai Kelawai between Nanga Pintas and about 3 km upstream, 0°36'49"N 111°47'22"E ; CMK 11755, 1 ex., 81.2 mm SL, Kapuas River drainage, Sungai Pala at Pala Hulu ( Kecamatan Siberuang , Kabupaten Renyai Hulu ) km 101 on road from Sintang to Putussibau ; MNHN 1982-704 , 4 ex., 84.0– 184.2 mm SL, Kapuas drainage, Sungai Tebelian, small forest stream 3–4 m wide and 50 cm deep where it flows into Sungai Pinoh , 19 km S of Nangapinoh ; USNM 232082 , 4 ex., 44.1–84.7 mm SL, rocky channel in mainstream of Sungai Pinoh , 37 km S of Nangapinoh ; ZMA 114.420 , 1 ex., 165.9 mm SL, Kapuas River at Bunut ; ZMA 114.419 , 1 ex., 196.9 mm SL, Kapuas River at Putussibau ; BMNH 1982.3.29.156–158, 2 ex., 129.6–190.0 mm SL, Sungai Paklehung, a low-lying forested hill stream to Sungai Mempawah, 48 km NNW from Pontianak , 9 km NE of Andjongan and 1–3 km upstream from Toho ; CMK 6691 , 1 ex., 92.6 mm SL, Sungai Mandor at Mandor (0°19'N 109°20'E) .

BORNEO: Kalimantan Tengah: ZRC 38859, 1 ex., 73.3 mm SL, Barito River between Mongkohol and Molosan ; ZRC 40042, 1 ex., 224.6 mm SL, Barito River drainage, Muara Teweh , Pasar Pendopo ; ZRC 40531, 1 ex., 98.4 mm SL, market in Purukcahu ;

BORNEO: Kalimantan Timur: RMNH 7552, 1 ex., 197.0 mm SL, Bo [holotype of Macrones fortis capitulum ]; ZRC 45519, 1 ex., 217.6 mm SL, Kayan drainage, Bahau, Lobok, a cut-off section of Bahau River near Kuala En’ggeng B’io, 2°52'16.8"N 115°49'28.8"E; ZRC 45525, 10 ex., 61.9–137.5 mm SL, Kayan drainage, Kayan River at mouth of Sungai Pingai; ZRC 45606, 1 ex., 186.4 mm SL, Kayan drainage, Bahau River; ZRC 45621, 2 ex., 49.1–68.2 mm SL, Kayan drainage, Bahau, Sungai Batu Bayak approx. 50 m upstream of Kuala En’ggeng B’io, 2°52'21.6"N 115°49'31.2"E; ZRC 45569, 1 ex., 122.0 mm SL, ZRC 45614, 2 ex., 161.4–177.6 mm SL, Mahakam drainage, main river upstream of Kota Bangun, 0°14'20.4"N 116°35'9.6"E; CAS 93909, 3 ex., 55.8–145.2 mm SL, Sungai Belayan, approx. 8–9 km upriver from Tabang; CAS 94726, 3 ex., 43.5–140.8 mm SL, Separi River on road from Samarinda to Sebulu (32 km from Air Putih crossroads); CAS 95051, 7 ex., 121.9–165.2 mm SL, small river on road 12.2 km from Sebulu crossroads); ZRC 40533, 10 ex., 281.4–375.0 mm SL, Samarinda; CMK 7633, 2 ex., 89.8–125.5 mm SL, Mahakam River drainage, stream connecting Mahakam River to Danau Semajang, 0°14’S 116°33’E; CMK 7687, 1 ex., 126.5 mm SL, Mahakam River drainage, swift stream entering Mahakam River downstream at Melak, 0°14'S 115°51'E; CMK 7704, 4 ex., 110.0– 133.8 mm SL, Mahakam River drainage, sandbank near Benanga, 0°7'S 115°46'E; CMK 7705, 2 ex., 76.8–90.2 mm SL, Mahakam River at Mujub, 0°2'S 115°43'E; CMK 7752, 1 ex., 97.1 mm SL, Mahakam River drainage, unnamed left-side blackwater tributary of Mahakam River about 2 km upriver of Mujub, 0°1'S 115°43'E; CMK 7798, 2 ex., 89.0–101.0 mm SL, Mahakam River drainage, swift black water stream entering Mahakam River downriver of Muarapahu at 0°14'S 116°7'E.

BORNEO: Kalimantan Selatan: ZRC 40022, 1 ex., 192.2 mm SL, Barito River drainage, Banjarmasin, Pasar Lima Beton ; ZRC 40070, 1 ex., 228.3 mm SL, Barito River drainage, Banjarmasin, Pasar Kuin ; ZRC 40084, 4 ex., 158.8–181.4 mm SL, Barito River drainage, market at Negara ; ZRC 40553, 7 ex., 270.0– 303.6 mm SL, Banjarmasin .

Diagnosis. — Hemibagrus capitulum differs from H. filamentus in having a relatively shorter and wider head (head width 59–70% HL vs. 56–60). It is distinguished from H. fortis in having the anteriormost branch of dorsal-fin rays longer than other branches (vs. branches of the dorsal-fin rays of almost equal length) giving the dorsal fin a jagged (vs. rounded) distal margin ( Fig. 20 ), from H. hoevenii in having the premaxillary tooth band not (vs. partially) exposed when the mouth is closed, rounded (vs. tapering) caudal-fin lobes, absence (vs. presence) of a broad and conspicuous dark margin around the caudal fin, a rounded (vs. triangular) anal fin, broader membranes of the dorsal fin which give it a rounded (vs. triangular) appearance, and filamentous extensions on the dorsal fin, when present, not reaching beyond middle of adipose-fin base (vs. very long filamentous extensions of the first two dorsal-fin rays, when present, that reach beyond the posterior base of the adipose fin), from H. nemurus in having a larger eye in specimens greater than approx. 150 mm SL (11–19% HL vs. 9–11), the adpressed dorsal fin (excluding the filamentous extensions of the fin rays if present) reaching to or beyond (vs. not reaching) the adipose-fin origin and longer maxillary barbels (reaching beyond caudal-fin base but frequently to vertical through base of last anal-fin ray vs. to origin of anal fin; 193–390% HL vs. 168–221), and from H. spilopterus in having a flat (vs. gently convex) interorbital space and the adpressed dorsal fin (excluding the filamentous extensions of the fin rays) reaching to or beyond (vs. not reaching) the adipose-fin origin.

Description. — Biometric and meristic data as in Table 12. General description as for genus. Head depressed and broad, body moderately compressed; head width 59–70% HL. Interorbital space flat. Eye diameter 11–19% HL. Premaxillary tooth band not exposed when mouth is closed. Dorsal profile rising evenly but not steeply from tip of snout to origin of dorsal fin, then sloping gently ventrally from there to end of caudal peduncle. Ventral profile horizontal to origin of anal fin, then sloping dorsally to end of caudal peduncle. Adipose-fin base short, approximately as long as anal-fin base; maximum height 4.3–6.5% SL (2.1–4.2 times in length of adipose-fin base). Adipose-fin origin separated from base of last dorsal-fin ray by distance of 7.0–14.6% SL. Dorsal spine stout, with 2–9 serrations on posterior edge. Anteriormost branch of each dorsal-fin ray longer than other branches, imparting jagged distal margin to fin; membranes broad, imparting rounded appearance. Adpressed dorsal fin (excluding filamentous extensions of rays) reaching to or slightly beyond adipose-fin origin; filamentous extensions, when present, not reaching beyond middle of adipose-fin base. Pectoral spine stout, with 6–15 large serrations on posterior edge. Anal fin rounded, origin slightly posterior to adipose origin. Caudal fin forked; upper and lower lobes rounded. Maxillary barbels reaching at least vertical through base of last anal-fin ray, sometimes beyond caudal-fin base (193–390% HL). Maximum recorded size 272 mm SL.

Colour. — Dorsal surface of head and body uniform brownish-grey (live or freshly-dead specimens sometimes with yellow hue, fading on preservation); ventral surface of head and body dirty white; adipose fin brownish-grey, sometimes with diffuse black spot; fin-rays and interradial membranes of all fins grey; dorsal surface of barbels brownish-grey, ventral surface dirty white.

Distribution. — Hemibagrus capitulum is known from river drainages in Borneo, the Malay Peninsula northwards to at least Narathiwat and Trang, and Sumatra ( Fig. 22 ). This species is absent from the upper reaches of river drainages in Borneo, where H. fortis is found instead. This species has been introduced to Singapore, where it is not native (reported as H. nemurus by Ng & Tan, 2010).

Habitat and biology. — Hemibagrus capitulum is found in a wide variety of lotic and lentic habitats. It is a predatory

species, with youngfish feeding preferentially on invertebrates (especially Crustacea), and older fish being more piscivorous ( Khan et al., 1988). It breeds during the rainy seasons ( Khan et al., 1990).

Remarks. — The oldest available name for this species is Macrones bleekeri Volz, 1903 , which is a primary junior homonym of Macrones bleekeri Day, 1877 (now Mystus bleekeri ). The next available name is Macrones capitulum Popta, 1904 .

We consider H. chrysops to be a junior synonym of H. capitulum , as the differences reported in Ng & Dodson (1999) are no longer as clear-cut once a larger series of material from throughout Sundaic Southeast Asia has been examined. There is a lack of a discernible pattern in the variation of the diagnostic characters reported by Ng & Dodson (1999), i.e. head width, length of adipose-fin base, dorsal to adipose distance and body colour. Despite evidence from a molecular analysis of a 300 bp fragment of the cyt b gene that indicates otherwise, we have chosen to synonymize H. chrysops with H. capitulum following overwhelming morphological evidence that indicates the two are conspecific. The cause(s) of the incongruence between the morphological and molecular data are not clear, but this is not the first instance that this phenomenon has been reported for freshwater fishes as a similar incongruence is observed in Mesoamerican cichlids ( Hulsey et al., 2004; Peréz et al., 2007).

Figures

Fig.23. Hemibagrus capitulum, ZRC 40482, 139.4 mm SL, Borneo: Brunei Darussalam, Sungai Merimbun.

Fig. 9. Hemibagrus macropterus, ZRC 53403, 117.5 mm SL; China: Suikou.

Fig. 4. Hemibagrus sabanus, ZRC 40493, 104.9 mm SL, Borneo: Sabah, Segama River.

Fig. 17. Map showing collection localities of Hemibagrus caveatus and H. peguensis specimens examined in this study

Fig. 6. Hemibagrus semotus, ZRC 46121, holotype, 126.0 mm SL, Borneo: Sabah, Padas River.

Fig.3. Map showing collection localities ofHemibagrus baramensis specimens examined in this study.

Fig. 21. Hemibagrus nemurus, ZRC 42564, 238.6 mm SL, Java: Sungai Sokan.

Fig. 20. Schematic illustrations of fully extended dorsal fins of members of the H. nemurus species group: a, H. fortis, ZRC 40522, 126.9 mm SL; b, other members of the H. nemurus species group (H. nemurus, ZRC 39181, 132.4 mm SL, illustrated). Scale bar = 10 mm.

Fig.22. Map showing collection localities of Hemibagrus nemurus, H. capitulum and H. filamentus specimens examined in this study.