Hemibagrus gracilis Ng & Ng, 1995

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 : 256-257

Hemibagrus gracilis Ng & Ng, 1995

( Fig. 35 )

Hemibagrus gracilis Ng & Ng, 1995: 136 , Figs. 1–3 , 4A (type locality: Sungai Jasin, Endau drainage, Malaysia); Ng & Tan, 1999: 357; Ferraris, 2007: 88; Ng & Lim, 2008: 28, Fig. 22 .

Macrones nemurus (non Valenciennes, in Cuvier & Valenciennes, 1840) - Duncker, 1904: 172.

Mystus planiceps (non Valenciennes, in Cuvier & Valenciennes, 1840) - Hora & Gupta, 1941: 27 (in part); Zakaria-Ismail, 1984: 25; 1987: 408; Kottelat et al., 1993: 66 (in part); Jayaram & Sanyal, 2003: 96.

Mystus aff. nemurus - Lim, Kottelat & Ng, 1990: 316; Lim, Ng & Kottelat, 1990: 44.

Mystus aff. planiceps - Lim et al., 1993: 6; Zakaria Ismail, 1993: 208, Pl. 5f.

Mystus cf. planiceps - Ng & Lim, 1994: 62.

Material examined. — PENINSULAR MALAYSIA: Johor: ZRC 21484, holotype, 247.0 mm SL; ZRC 21482, 21486–21487 ; 3 paratypes, 162.0–214.0 mm SL, Ulu Endau, Sungai Jasin .

PENINSULAR MALAYSIA: Pahang: ZRC 8294–8295 , 2 paratypes, 236.0, 266.0 mm SL ; ZRC 8757–8759 , 3 paratypes, 230.0–277.0 mm SL, Rompin, Sungai Kinchin .; ZRC 8296 , 1 paratype, 198.0 mm SL, Rompin, Sungai Kinchin at confluence of Sungai Selindang ; ZRC 8726–8728 , 3 paratypes, 182.0–264.0 mm SL, Rompin, Sungai Kernam (tributary of Sungai Kinchin) ; ZRC 8752–8753 , 2 paratypes, 295.0–405.0 mm SL, Johor – Pahang border, Sungai Taku (tributary of Sungai Endau); FMNH 62308 , 1 ex., 73.6 mm SL, King George V National Park ; FMNH 62307 , 1 ex., 179.7 mm SL, Sungai Tahan . ZRC 2436 , 1 ex., 140.7 mm SL, Sungai Lumpat ; ZRC 2438 , 1 ex., 113.0 mm SL, Kuala Tahan ; ZRC 3233 , 1 ex., 69.0 mm SL, 0.5 mile up Sungai Tahan ; ZRC 2422 , 1 ex., 113.0 mm SL, Ulu Jelai ; ZRC 42629, 1 ex., 260.5 mm SL, Sungai Kinchin near mouth of Sungai Kernam .

Diagnosis. — Hemibagrus gracilis differs from H. bongan in having a shorter snout (30–35% HL vs. 33–41), and more vertebrae (50–52, mode=52 vs. 48–50, mode=49), from H. divaricatus in having a deeper adipose fin (maximum height 2.9–4.3 times in length of base vs. 1.9–3.2), a more slender caudal peduncle (depth 6.2–7.6% SL vs. 7.3–8.0) and a larger eye (17–21% HL vs. 11–17), and from H. lacustrinus in having a longer dorsal to adipose distance (10.6–16.8% SL vs. 7.6–10.9; adpressed dorsal fin reaching vs. not reaching origin of adipose fin), a more slender caudal peduncle (depth 6.2–7.6% SL vs. 7.3–8.1) and more vertebrae (50–52, mode=52 vs. 49–50, mode=49). It is distinguished from H. planiceps in having more vertebrae (50–52, mode=52 vs. 47–49, mode=47), a more slender caudal peduncle (depth 6.2–7.6% SL vs. 7.1–8.6), a shorter snout (30–35% HL vs. 33–40) and longer maxillary barbels (216–278% HL vs. 148–220), and from H. velox in having a relatively shorter genital papilla in the males (not reaching anal-fin origin, vs. reaching), the genital papilla located further away from the anus (anus separated from genital papilla by a distance of 5.4–7.6% SL vs. 4.3–5.9) and regular (vs. irregular) serrations on the posterior edge of the dorsal spine.

Description. — Biometric and meristic data as in Table 21. General description as for genus. Head depressed and broad, body moderately compressed. Snout length 30–35% HL. Interorbital distance 29–34% HL. Eye diameter 17–21% HL. 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. Body depth at anus 8.4–13.5% SL. Adipose-fin base short, approximately as long as anal-fin base (13.5–17.4% SL); maximum height 2.9–4.3 times in length of base; separated from base of last dorsal-fin ray by distance of 10.6–16.8% SL. Dorsal spine stout, with 0–9 serrations on posterior edge; length 8.6–13.5% SL. Adpressed dorsal fin not reaching adipose-fin origin. Pectoral spine stout, with 12–23 large serrations on posterior edge; length 14.5–17.0% SL. Anal-fin origin slightly posterior to adipose origin. Caudal-peduncle depth 6.2–7.6% SL. Caudal fin forked; upper lobe tapering with principal ray produced into a filament, lower lobe rounded posteriorly. Maxillary-barbel length 216–278% HL. Inner mandibular-barbel length 38–53% HL. Vertebrae 50–52. Branchiostegal rays 10–11. Maximum recorded size 405 mm SL.

Males with elongate genital papilla not reaching to origin of anal fin. Anus separated from genital appendages of both sexes by 5.4–7.6% SL.

Colour. — Dorsal surface of head and body uniform light grey to grey (live or freshly-dead specimens with yellowish hue, fading in preserved specimens); lateral line cream to yellow; ventral surface of head and body dirty white; adipose

fin and fin rays of all fins grey; inter-radial membranes of all fins dirty yellow.

Distribution. — Known from the Endau and Pahang River drainages in eastern Peninsular Malaysia ( Fig. 32 ).

Figures

Fig. 35. Hemibagrus gracilis, ZRC 21484, holotype, 247.0 mm SL, Peninsular Malaysia: Sungai Jasin.

Fig. 1. Method of measurements used in this study: 1, Standard length; 2, Predorsal length; 3, Preanal length; 4, Prepelvic length; 5, Prepectoral length; 6, Dorsal-spine length; 7, Dorsal-fin length; 8, Length of dorsal-fin base; 9, Length of anal-fin base; 10, Pelvic-fin length; 11, Pectoral-fin length; 12, Pectoral-spine length; 13, Caudal-fin length; 14, Length of adipose-fin base; 15, Maximum height of adipose fin; 16, Dorsal to adipose distance; 17, Post-adipose distance; 18, Length of caudal peduncle; 19, Depth of caudal peduncle; 20, Body depth at anus; 21, Head length; 22, Head width; 23, Head depth; 24, Snout length; 25, Interorbital distance; 26, Eye diameter.

Fig.2. Hemibagrus baramensis, ZRC 42742, 150.0 mm SL; Borneo: Sarawak, Mulu.

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

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

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

Fig.32. Map showing collection localities ofHemibagrus planiceps, H. bongan, H. divaricatus, H. gracilis, H. lacustrinus, and H. velox specimens examined in this study.