Clarias olivaceus ( Fowler, 1904 )

Ng, H. H. Tan H. H., 2000, The cat ® shes (Teleostei: Siluriformes) of central Sumatra, Journal of Natural History 34, pp. 267-303 : 292-294

Clarias olivaceus ( Fowler, 1904)

(®gure 9)

Chlarias olivaceus Fowler, 1904: 499 (type locality: Padang , Sumatra).

? Clarias fuscus (non La Ce ÂpeÁde, 1803): Bleeker, 1854: 65; 1858a: 25 1860a: 49; 1862: 105.? Clarias melanoderm a (non Bleeker, 1846): Vinciguerra, 1879: 386.

? Clarias leiacanthus (non Bleeker, 1851): Weber and de Beaufort, 1912: 533; 1913: 192; Kottelat et al., 1993: 77.

Clarias teysmanni (non Bleeker, 1857): Regan, 1920: 308.

Material examined. BATANG HARI DRAINAGE: ZRC 41697 (8), 116.2±231.7 mm SL. ZRC 42562 (2), 150.5, 177.6 mm SL. ZRC 43236 (3), 150.5±223.8 mm SL.

WEST SUMATRA DRAINAGES: ANSP 27280 (1), holotype, 241.8 mm SL. ANSP 27281 (3), paratypes, 157.5±209.5 mm SL .

Description. Body relatively short, cylindriform; in % SL: body depth at anus 13.4±15.9, predorsal length 32.6±36.5, preanal length 48.3±55.4, prepelvic length 41.3±49.1, prepectoral length 18.4±19.5, dorsal-®n length 63.9±72.3, anal-®n length 47.2±52.5, pelvic-®n length 7.3±9.0, pectoral-®n length 11.2±14.5, length of pectoral spine 7.3±10.3, distance between occipital process and dorsal ® n 8.4 ±11.1, depth of caudal peduncle 6.5±8.2, caudal-®n length 12.5±15.2, head length 23.8 ±26.0, head width 16.0±18.8, head depth 9.2±13.8; in % HL: snout length 26±36, interorbital distance 41±45, length of nasal barbel 58±81, length of maxillary barbel 93±118, length of inner mandibular barbel 55±75, length of outer mandibular barbel 75±100, length of anterior fontanelle 10±17, width of anterior fontanelle 3±6, length of occipital fontanelle 7±9, width of occipital fontanelle 4±5, length of occipital process 10±17, width of occipital process 26±37. Skin smooth. Lateral line median, beginning just after the operculum and ending at the caudal peduncle. Anterior fontanelle short and squat (`sole-shaped’ of Teugels, 1986), the anterior edge reaching an imaginary line connecting the anterior orbital borders. Occipital fontanelle oval, narrower than anterior fontanelle, the posterior edge reaching an imaginary line connecting the base of the pectoral spines. Eye small and subcutaneous, diameter 5±6% HL. Four pairs of barbels present, with thick ¯eshy base, gradually tapering towards tips. Nostril tube long, extending beyond edge of the mouth when directed forwards. Gill rakers 4 +9= 13 (1), 1 +14 = 15 (1), 4 +12 = 16 (1), 3 +14 = 17 (1), 3 +15 = 18 (1) or 4 +16 = 20 (1). Branchiostegal rays 8 (6) or 9 (1). Vertebral formula 21 +39 = 60 (1), 21 +40 = 61 (2), 21 +41 = 62 (2), 22 +40 = 62 (1) or 22 +41= 63 (1).

Fin-ray counts: pectoral I, 9 (3); I, 9, (3) or I, 10, i (1); dorsal 62 (1), 63 (3), 64 (1) or 66 (2); pelvic i, 5 (7); anal 49 (1), 51 (1), 52 (2), 53 (2) or 54 (1); caudal 8/8 (7). Pectoral spine broad, covered by skin, anterior margin with small inward directed serrae (®gure 10a); ®rst dorsal-®n ray shortest, last few rays progressively shorter, posterior part rounded, not joined to caudal ®n; ®rst anal-®n ray shortest, last few rays progressively shorter, posterior part rounded, not joined to caudal ®n; caudal ®n rounded.

Colour. Preserved specimens (in 10% formalin) are a uniform dark grey with small black spots randomly distributed on sides of body, paler on the undersides. Dorsal, caudal and anal ®ns the colour of the body, pelvic and pectoral ®ns opaque white to hyaline. Fin rays dusky.

Remarks. The exact taxonomic status of Clarias olivaceus has not been well understood to date. Examination of the type specimens and fresh material collected from near the type locality have revealed that C. olivaceus is in fact a valid species.

Clarias olivaceus di ers from C. nieuho ®i by its relatively shorter body with 62±66 dorsal-®n rays (vs relatively long body with 87±106 dorsal-®n rays). It can be di erentiated from all other Southeast Asian Clarias by the presence of relatively large and distinct serrations on the anterior edge of the pectoral spine (vs without serrations or with anterior edge of pectoral spine rugose which in extreme cases is manifested as a series of low asperities; ®gure 10) and uniformly dark body coloration without any pale spots on the body (vs with pale spots present). Clarias olivaceus further di ers from C. teijsmanni Bleeker, 1857 (with C. thienemanni Ahl, 1934 as a junior synonym) and C. leiacanthus in having fewer dorsal-®n rays (62±66 vs 68±74). In the original description, Fowler (1904) gives the gill raker counts as 9 (5 +4); this extremely low gill raker count may be due to a typographical error or it could simply mean that the counts were obtained from an aberrant specimen.

The only other species of Southeast Asian Clarias with relatively large and distinct serrations on the anterior edge of the pectoral spine is C. meladerma , but the serrations on C. meladerma are larger (®gure 10) and can be felt through the thick skin covering the pectoral spine, whereas those of C. olivaceus are smaller and cannot be felt. In any case, C. meladerma further di ers from C. olivaceus in having a shorter distance between the tip of the occipital process and the base of the ®rst dorsal-®n ray (2.1±4.7% SL vs 8.4 ±11.1)

Clarias olivaceus is known from the highlands in western Sumatra as far north as Lake Toba (USNM 193033). A partially depigmented individual of this species was found in our series of specimens. This specimen had a variegated body pattern consisting of cream and grey patches (®gure 9).