Clarias nigricans, Ng, 2003

Ng, Heok Hee, 2003, Clarias Nigricans, A New Species Of Clariid Catfish (Teleostei: Siluriformes) From Eastern Borneo, Raffles Bulletin of Zoology 51 (2), pp. 393-398 : 393-396

publication ID	https://doi.org/ 10.5281/zenodo.13229237
DOI	https://doi.org/10.5281/zenodo.13229346
persistent identifier	https://treatment.plazi.org/id/56766B4A-333D-FF97-FC33-DB403601F558
treatment provided by	Felipe
scientific name	Clarias nigricans
status	sp. nov.

Treatment

Clarias nigricans View in CoL , new species

( Figs. 1 View Fig , 2 View Fig , 3a View Fig )

Clarias nieuhofi – Weber & de Beaufort, 1913: 189 (in part) (non Valenciennes).

Material examined. – Holotype – MZB 10705, 307.5 mm SL, Borneo: Kalimantan Timur, market in Samarinda, coll. H. H. Tan & D. Wowor, 7 Nov.1999.

Paratypes – 5 ex., 232.4–305.0 mm SL, ZMA 121.631 View Materials , Borneo: Kalimantan Timur, Samarinda, coll. H. J. Lorentz, 20 May.1909 ; 2 ex., 197.4–315.1 mm SL, ZRC 45590 View Materials , data as for holotype .

Diagnosis. – Clarias nigricans can be distinguished from congeners of the C. nieuhofii species group in having a narrow snout (with an egg-shaped head when viewed dorsally), dark violet grey coloration with small white spots on flanks, a narrow head (11.7–12.3% SL), a relatively large distance between the tip of the occipital process and the base of the first dorsal fin ray (8.1–9.8% SL), and few large serrations on the anterior edge of the pectoral spine.

Description. – Head depressed; dorsal profile slightly convex and ventral profile almost straight. Bony elements of dorsal surface of head covered with thick skin; bones not readily visible, but sutures sometimes evident. Front fontanel short and squat (“sole-shaped” of Teugels, 1986); anterior tip reaching just posterior to line through posterior orbital margins. Occipital process acutely rounded. Eye ovoid, horizontal axis longest, subcutaneous; located dorsolaterally on head. Gill openings narrow, extending from dorsalmost point of pectoral-fin base to isthmus. Gill membranes free from but united to each other across isthmus, with 9 (n=7) or 10 (n=1) branchiostegal rays. First branchial arch with 3+15 (n=2) gill rakers.

Mouth subterminal, with fleshy, plicate lips. Oral teeth small and in irregular rows on all tooth-bearing surfaces. Premaxillary tooth band rectangular, with median notch on posterior edge. Dentary tooth band much narrower than premaxillary tooth band at symphysis, tapering laterally. Vomerine tooth band unpaired, continuous across midline; crescentic and smoothly arched along anterior margin, posterior margin with a median posteriorly-directed process. Premaxillary and dentary teeth viliform, vomerine teeth subgranular.

Barbels in four pairs; long and slender with thick fleshy bases. Maxillary barbel extending nearly to base of first dorsal-fin ray. Nasal barbel, extending nearly to tip of occipital process. Inner mandibular-barbel origin close to midline; barbel thicker and longer than nasal barbel and extending to base of pectoral spine. Outer mandibular barbel originates posterolateral of inner mandibular barbel, extending to tip of pectoral fin.

Body cylindrical, becoming compressed towards caudal peduncle. Dorsal profile rising gently from tip of snout to origin of dorsal fin and thereafter almost horizontal to end of caudal peduncle. Ventral profile slightly convex to middle of head and thereafter almost horizontal to end of caudal peduncle.

Skin smooth. Lateral line complete and midlateral in position. Vertebrae 21+55=76 (n=1), 21+57=78 (n=1), 22+56=78 (n=1), 22+58=80 (n=1), 24+57=81 (n=1), 23+59=82 (n=1), 24+58=82 (n=1) or 23+60=83 (n=1).

Dorsal fin with long base, spanning posterior three-quarters of body; with 92 (n=1), 93 (n=1), 94 (n=3), 95 (n=1) or 97 (n=2) rays covered by thick layer of skin and without spine. Dorsal-fin margin straight, parallel to dorsal edge of body. Dorsal fin confluent with caudal fin along most of posteriormost dorsal-fin ray.

Pectoral fin with small spine, sharply pointed at tip, and 7,i (n=8) rays. Proximal three-quarters of anterior spine margin with large serrations; distal quarter of anterior spine margin and posterior spine margin smooth. Pectoral-fin margin straight anteriorly, convex posteriorly.

Pelvic-fin origin at anterior third of body, with i,5 (n=8) rays and convex margin; tip of adpressed fin reaching base of first few anal-fin rays. Anus and urogenital openings located at vertical through middle of adpressed pelvic fin.

Anal fin with long base and 80 (n=2), 82 (n=2), 84 (n=3) or 86 (n=1) rays covered by thick layer of skin; margin straight and parallel to ventral edge of body. Anal fin confluent with caudal fin along most of posteriormost anal-fin ray.

Caudal peduncle short. Caudal fin rounded, with i,5,5,i (n=3), i,6,5,i (n=4) or i,6,6,i (n=1) principal rays.

Morphometric data as in Table 1.

Colour. – Dorsal and lateral surfaces of head and body dark violet grey, fading to pale grey on ventral surfaces. Thirteen to fourteen vertical rows of two to five minute white spots present, subtended ventrally with an irregular row of minute white spots running just below lateral line. Dorsal and caudal fins dark violet grey with very thin hyaline distal margin. Anal fin light grey, with thin hyaline distal margin. Pectoral-fin rays dark violet grey, with hyaline interradial membranes. Pelvic fins hyaline. Barbels and pectoral spines dark violet grey dorsally and light grey ventrally.

Etymology. – The Latin adjective nigricans, meaning blackish. In reference to the relatively dark colour of this species.

Distribution. – Known only from the Mahakam drainage in eastern Borneo.