Hemibagrus lacustrinus, 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 : 257-258

Hemibagrus lacustrinus new species

( Fig. 36 )

Macrones planiceps (non Valenciennes, in Cuvier & Valenciennes, 1840) - Weber and de Beaufort 1913: 342–343 (in part).

Hemibagrus velox (non Tan & Ng, 2000) - Tan & Ng, 2000: 272 (in part).

Holotype. — MZB 17183, 135.3 mm SL, Sumatra: Sumatera Barat, Hulu Batang Ombilin, coll. D. Roesma, 2007.

Paratypes. — CMK 4625 , 3 ex., 78.1–143.0 mm SL, Sumatra: Sumatera Barat, market at Solok , coll. P. G. Bianco & M. Kottelat, 4 Dec.1984 ; UMMZ 243355 , 1 ex., 122.8 mm SL, Sumatra: Sumatera Barat, market at Solok , 0°48'S 100°39'E, coll. H.H. Ng et al., 16 Dec.2003 ; UMMZ 155684 , 2 ex., 183.7, 194.8 mm SL, Sumatra: Sumatera Barat, Danau Singkarak , coll. A. Thienemann, 23 Feb.1929 ; ZMA 121.812 , 2 ex., 179.8–223.2 mm SL, Sumatra: Sumatera Barat, Danau Singkarak ; ZRC 51974, 1 ex., 155.5 mm SL; data as for holotype .

Diagnosis. — Hemibagrus lacustrinus differs from all members of the H. planiceps species group in having a shorter dorsal to adipose distance (7.6–10.9% SL vs. 10.6–17.6; adpressed dorsal fin reaching vs. not reaching the origin of the adipose fin) and (except for H. bongan and H. planiceps ) a longer adipose-fin base (18.8–20.4% SL vs. 11.1–17.9). It is further distinguished from H. bongan in having a deeper body (depth at anus 12.2–13.6% SL vs. 9.5–12.9), and from H. divaricatus in having a deeper adipose fin (maximum height 4.1–6.0 times in length of base vs. 1.9–3.2) and larger eye (17–19% HL vs. 11–17). Hemibagrus lacustrinus further differs from H. gracilis in having a deeper caudal peduncle (7.3–8.1% SL vs. 6.2–7.6) and slightly fewer vertebrae (49–50, mode=49 vs. 50–52, mode=52) and H. planiceps in having a smaller interorbital distance (30–32% HL vs. 32–37) and slightly more vertebrae (49–50, mode=49 vs. 47–49, mode=47).

Description. — Biometric and meristic data as in Table 22. General description as for genus. Head depressed and broad, body moderately compressed. Snout length 33–38% HL. Interorbital distance 30–32% HL. Eye diameter 17–19% 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 12.2–13.6% SL. Adipose-fin base short, approximately as long as anal-fin base (18.8–20.4% SL); maximum height 4.1–6.0 times in length of base; separated from base of last dorsal-fin ray by distance of 7.6–10.9% SL. Dorsal spine stout, with 2–3 serrations on posterior edge; length 10.7–12.6% SL. Adpressed dorsal fin not reaching adipose-fin origin. Pectoral spine stout, with 8–13 large serrations on posterior edge; length 15.0–16.7% SL. Anal-fin origin slightly posterior to adipose origin. Caudalpeduncle depth 7.3–8.1% SL. Caudal fin forked; upper lobe tapering with principal ray produced into a filament, lower lobe rounded posteriorly. Maxillary-barbel length 141–247% HL. Inner mandibular-barbel length 42–52% HL. Vertebrae 49–50. Branchiostegal rays 10. Maximum recorded size 223 mm SL.

Males with elongate genital papilla reaching to origin of anal fin. Anus separated from genital appendages of both sexes by 4.1–7.9% SL.

Colour. — Dorsal surface of head and body uniform grey or dark grey (becoming dark brownish on preservation); lateral line paler; 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 lacustrinus , meaning of a lake, in reference to the primary habitat of this species (a tectonic lake).

Distribution. — Known only from Danau Singkarak, a lake in central west Sumatra; this species is also found in the upper Ombilin River, which is a natural outflow of the lake ( Fig. 32 ).

Habitat. — Danau Singkarak is a relatively deep (maximum depth 286 m) tectonic lake with a surface area of 107.8 square kilometres located on the Barisan range in western Sumatra ( Verstappen, 1961; Zen, 1971). The microhabitats in the lake that the catfish occupies are not known, but it is believed that this species inhabits the inshore areas of the lake. The upper Ombilin River where this catfish occurs is relatively swift flowing, with a substrate of gravel and rock.

Remarks. — Hemibagrus lacustrinus is found sympatrically with H. velox : nearly all the paratypes of H. lacustrinus (except for ZRC 51974) have been misidentified by Tan & Ng (2000) as H. velox . As given in the diagnosis, H. lacustrinus differs from H. velox in having a shorter dorsal to adipose distance (7.6–10.9% SL vs. 13.2–17.5; adpressed dorsal fin reaching vs. not reaching the origin of the adipose fin) and a longer adipose-fin base (18.8–20.4% SL vs. 13.0–17.9). It is also distinguished from H. velox by the darker colouration of the head and body. However, given the paucity of material of this species, it is premature to conclude that this is a useful diagnostic character, since in our experience, the colour of Hemibagrus may vary greatly depending on water conditions and type of substrate.

Figures

Fig. 36. Hemibagrus lacustrinus, MZB 17183, holotype, 135.3 mm SL, Sumatra: Hulu Batang Ombilin.

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