Nanobagrus stellatus, Ng, 2000

Ng, H. H. Tan H. H., 2000, The cat ® shes (Teleostei: Siluriformes) of central Sumatra, Journal of Natural History 34, pp. 267-303 : 278-280

Nanobagrus stellatus , sp. nov.

(®gure 5a)

HOLOTYPE. MZB 9306 , 23.0 mm SL; Jambi: Sg. Alai (from aquarium collectors); H. H. Tan et al., 14 June 1996.

(a) (b)

PARATYPES. ZRC 42546 (3), 23.2±33.6 mm SL; data as for holotype . CMK 14811 (1), 21.1 mm SL; locality as for holotype ; 1998.

Comparative material. N. armatus: CAS 49371 (2), 19.2, 25.3 mm SL; Borneo: Kalimantan Barat, Kapuas river basin, Sungai Belimbing, large forested stream 46 km SSE of Sintang and 15 km by road WNW of Nangaipinoh. CAS 49372 (3), 18.1±21.2 mm SL; USNM 230278 (4), 16.2 ±19.5 mm SL; Borneo: Kalimantan Barat, Kapuas river basin, Sungai Mandai Ketchil near its conūence with Kapuas mainstream, 18 km WSW of Putussibau. CMK 6915 (3), 20.3±28.6 mm SL; Borneo : Kalimantan Barat, right tributary of Sungai Sibau , about 3 km upstream of Putussibau .

Diagnosis. A species of Nanobagrus with a slender body (body depth at anus 14.1±15.9% SL), short adipose-®n base (length of adipose-®n base 12.8±16.4% SL), large eyes (eye diameter 12.3±16.1% HL) and 34±36 vertebrae; body brown with three rows of cream-coloured spots located (on both sides) above, along and below the lateral line.

Description. Head depressed and broad, body moderately compressed. Dorsal pro®le rising evenly but not steeply from tip of the snout to origin of the dorsal ®n, then sloping gently ventrally from there to the end of the caudal peduncle. Ventral pro®le horizontal to origin of anal, then sloping dorsally to the end of the caudal peduncle. In % SL: head length 24.1±26.3, head width 19.9±24.8, predorsal distance 34.5±38.7, preanal length 61.0±62.5, prepelvic length 46.6±48.3, prepectoral length 19.9±23.9, body depth at anus 14.1±15.9, length of caudal peduncle 17.7±18.5, depth of caudal peduncle 9.8 ±11.2, pectoral-®n length 19.6±23.3, length of dorsal-®n base 12.9±14.7, pelvic-®n length 15.3 ±16.5, length of anal-®n base 17.7±18.8, caudal-®n length 36.6±40.0, length of adipose-®n base 12.8±16.4, dorsal to adipose distance 19.6±24.4; in % HL: snout length 33.3±39.5, interorbital distance 34.4±42.0, eye diameter 12.3±16.1, nasal barbel length 76.7±101.6, maxillary barbel length 118.0± 182.7, inner mandibular barbel length 77.8±93.3, outer mandibular barbel length 96.9±121.7. Branchiostegal rays 5 (3) or 6 (1). Gill rakers 2 +7 (1). Vertebrae 16 +18= 34 (1), 16 +19 = 35 (1) or 17 +19 = 36 (2).

Fin ray counts: dorsal I, 6, i (1), I, 7 (2) or I, 8 (1); pectoral I, 5, i (1) or I, 6 (3); pelvic ii, 4, i (4); anal v, 8, i (1), iii, 9, i (1) or v, 9, i (2); caudal 8/9 (4). Dorsal origin nearer tip of snout than caudal ¯exure. Pectoral spine stout, with 7 (1), 8 (1) or 10 (2) large serrae posteriorly. Anal origin slightly posterior to adipose origin. Depressed dorsal not reaching adipose ®n. Caudal ®n forked.

Colour. Dorsal surface and sides of head and body brown. Belly, chest and ventral surface of the head cream. Dorsal surface of head with cream-coloured spots located posterior to the eyes. Occipital region sometimes cream. A longitudinal row of 10±13 cream-coloured spots located on both sides of the body along the lateral line. A second and third similar row of six to seven cream-coloured spots located on both sides of the body above and below the lateral line, respectively. Dorsal, anal and caudal ®n membranes hyaline with brown ®n rays. Pectoral and pelvic ®ns hyaline. Barbels and pectoral spines brown on dorsal surface and cream on ventral surface.

Etymology. From the Latin stellatus , meaning starred or spotted, in reference to the pattern of cream-coloured spots on the body.

Remarks. Mo (1991) erected the genus Nanobagrus for bagrids with seven pelvic- ®n rays, reduced supraoccipital process and interneural, six to eight gill rakers, ®ve to six pectoral-®n rays, presence of the retractor tentaculi muscle, the ®fth vertebra bearing ribs and seven soft dorsal-®n rays but ®ve free proximal radials. Nanobagrus was previously considered monotypic, with Akysis armatus Vaillant, 1902 , being the only described species.

Nanobagrus stellatus di ers from N. armatus in having a more slender body (body depth at anus 14.1±15.9% SL vs 16.0±21.0), shorter adipose-®n base (length of adipose-®n base 12.8±16.4% SL vs 16.5±21.6), larger eyes (eye diameter 12.3±16.1% HL vs 9.0±12.5) and more vertebrae (34±36 vs 33±34). The colour patterns of the two species also di er: N. armatus has a brown body with a series of cream-coloured spots along the lateral line, another two longitudinal rows of cream-coloured spots are located above and below the lateral lines and two relatively large and irregular cream-coloured patches on the sides of the body while in N. stellatus , the pattern consists of a brown body with a series of cream-coloured spots along the lateral line, another two longitudinal rows of cream-coloured spots are located above and below the lateral lines, respectively (compare ®gures 5a and 5b). The species are geographically separate, with N. armatus known from the Mahakam and Kapuas drainages in Borneo while N. stellatus is known currently from the Batang Hari drainage in Sumatra.