Hemibagrus semotus, Ng & Kottelat, 2013

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 : 215-216

Hemibagrus semotus new species

( Fig. 6 )

Mystus baramensis (non Regan, 1906) – Inger & Chin, 1962: 139, Fig. 70 (in part); Gosse, 1972: 2; Chin, 1996: 305, Fig. 19 .

Holotype. — ZRC 46121, 126.0 mm SL, Borneo: Sabah, Padas River at Tenom, coll. J. Dodson, 28 Apr.1998.

Paratypes. — FMNH 96272 , 1 ex., 192.0 mm SL, Borneo : Sabah, Kota Kinabalu, coll. P. K. Chin, date unknown . ZRC 46122, 9 ex., 128.9–198.8 mm SL, data as for holotype . ZRC 46789, 1 ex., 84.6

mm SL; Borneo: Sabah, Sipitang, Sungai Malamum, tributary of Mengalong River, coll. H. H. Tan et al., 9 Dec.2000.

Diagnosis. — Hemibagrus semotus is distinguished from H. baramensis in having a greater dorsal to adipose distance (8.2–10.2% SL vs. 4.7–8.6), an anal fin with a straight distal margin, imparting a more rhomboidal appearance (vs. with a convex distal margin, imparting a more rounded appearance) and the upper lobe of the caudal fin regularly tapering (vs. rounded posteriorly). It differs from H. sabanus in having a smaller adipose fin located further away from the dorsal fin (length of adipose-fin base 19.3–3.5% SL vs. 8.9–34.3; dorsal to adipose distance 8.2–10.6% SL vs. 1.2–4.4), a deeper caudal peduncle (depth 9.6–11.3% SL vs. 7.2–9.4), and a shorter outer mandibular barbel (81.9–120.1% HL vs. 127.5–162.1).

Description. — Biometric and meristic data as in Table 3. General description as for genus. Head depressed and broad, body moderately compressed. 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. Caudal-peduncle depth 9.6–11.3% SL. Adipose-fin base moderately long, about 2.0–2.5 times anal-fin base (19.3–23.4% SL); distance from origin to base of last dorsal-fin ray 8.2–10.2% SL. Dorsal spine stout, with 4–7 serrations on posterior edge. Adpressed dorsal fin reaching adipose fin; second ray not extended, imparting rounded appearance to fin. Pectoral spine stout, with 10–14 large serrations on posterior edge. Anal-fin origin slightly posterior to adipose origin, with straight distal margin. Caudal fin forked; upper lobe tapering with principal ray produced into filament, lower lobe rounded posteriorly. Outer mandibular-barbel length 81.9–120.1% HL. Maximum recorded size 199 mm 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.

Etymology. — From the Latin adjective meaning pushed aside ( semotus ); in reference to the relatively large distance between the dorsal and adipose fins.

Distribution. — Hemibagrus semotus is known from the Padas River drainage and the shorter coastal rivers draining

the western face of the Crocker Range in northern Borneo ( Fig. 5 ).

Habitat and biology. — Hemibagrus semotus has been collected in slow-flowing streams with turbid water and a substrate of mud and gravel at elevation ( Gosse, 1972). The species feeds primarily on arthropods (Inger & Chin, 1962).

Figures

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

Fig. 19. a, Hemibagrus punctatus, ZSI FF 1223, 193.1 mm SL; India: Hemavathy River; b, Specimen (not preserved) from Cauvery River, Karnataka (approx. 250 mm SL) showing live colouration. (Photograph courtesy of Johnny Jensen; copyright www.jjphoto.

Fig. 5. Map showing collection localities of Hemibagrus sabanus and H. semotus specimens examined in this study.