Rasbora tornieri Ahl, 1922

Ng, Heok Hee & Kottelat, Maurice, 2013, The identity of the cyprinid fishes Rasbora dusonensis and R. tornieri (Teleostei: Cyprinidae), Zootaxa 3635 (1) : -

Rasbora tornieri Ahl, 1922

( Figs. 1 b, 2b)

Rasbora tornieri Ahl, 1922: 32 (type locality: Central Sumatra); Kottelat et al., 1993: pl. 20.

Rasbora dusonensis (non Bleeker)—Brittan, 1954: 122, Fig. 26; Rainboth, 1996: 77, Pl. V Fig. 34.

Material examined. ZMB 20542 (lectotype), 54.5 mm SL; Sumatra: Central Sumatra [Siak/Rokan river drainage].—UMMZ 232649 (4), 51.3–58.4 mm SL; Cambodia: Kandal, Prek Lo Prampi just upstream from Phum Khleang, at fishing lots 6 and 7, 11°10'N 105°9'E.—CMK 20593 (28), 27.2–74.1 mm SL; ZRC 53469 (26), 40.1–73.8 mm SL; Sumatra: Sumatera Selatan, Sungai Gelam, ca. 1 hour downriver from Kenten Laut (Palembang), 2°50'14.6"S 104°47'49.1"E.—CMK 7323 (15), 26.2–59.8 mm SL; Sumatra: Riau: Sungei Siak Kecil, small blackwater canal entering mainstream, 1°09'N 102°02'E.—ZRC 42726 (5), 43.9–89.2 mm SL; Brunei: Belait District, base camp at Sungei Ingei, 4°9'42.6"N 114°42'59.5"E.—ZRC 49994 (25), 11.0– 80.3 mm SL; Borneo: Kalimantan Barat, Kabupaten Sambas, Sungai Sambas, 1°21'46.2"N 109° 18'28.8"E.

Diagnosis. Rasbora tornieri and R. dusonensis are distinguished from congeners in having a broad, darkbrown sharply-defined midlateral stripe on body extending from opercle to caudal-fin base and separated from dark brown supralateral stripe and dorsum by highly contrasting light longitudinal area. The following characters (none unique) also help in identifying them: 12-14 predorsal scales; dorsohypural distance equal to or slightly less than distance between dorsal-fin origin and posterior orbital margin; 14 circumpeduncular scales; brightly coloured caudal fin in life. Rasbora tornieri differs from R. dusonensis in having a carmine red caudal fin without or with a very narrow black posterior margin (vs. bright yellow with a broad black posterior margin), and a deeper caudal peduncle (7.9–8.8 times in SL vs. 8.5–9.6; 11.4–12.7% SL vs. 10.4–11.7).

Description. Morphometric data are given in Table 1 , meristic data in Table 2 . Body slender, elongate, laterally compressed, its greatest depth between pelvic-fin insertion and dorsal-fin origin. Dorsal profile of head sloping evenly from margin of upper lip to supraoccipital. Snout acutely rounded. Dorsal profile of body slightly convex from supraoccipital to dorsal-fin origin, thereafter slightly concave to caudal-fin base. Ventral profile gently convex from margin of lower lip to pelvic-fin origin, with slight concavity at isthmus; almost horizontal between pelvic- and anal-fin origins and gently concave at caudal peduncle. Mouth oblique, superior. Symphyseal knob on dentary strongly developed, fitting into corresponding indentation between premaxillae.

Scales cycloid. Lateral line complete (all scales perforated; 27–30+2) its anterior portion curving ventrally. Dorsal fin pointed at tip, with slightly convex posterior margin. Dorsal-fin origin posterior to vertical through base of last pelvic-fin ray. Dorsohypural distance equal to or slightly less than distance between dorsal-fin origin and posterior orbital margin. Pectoral-fin subtriangular, with subrectangular axillary lobe dorsal to base of first unbranched ray. Tip of adpressed pectoral fin just reaching vertical through pelvic-fin insertion. Pelvic-fin profile triangular, with lanceolate axillary scale located dorsal to pelvic-fin base. Tip of adpressed pelvic fin reaching to anus. Anal fin with falcate posterior margin. Caudal fin deeply forked, with acutely pointed asymmetrical lobes, lower lobe longer.

Coloration. In 70% ethanol: Dorsal and dorsolateral surfaces of head and body brown; ventrolateral and ventral surfaces unpigmented. Opercle pale brown dorsally, with distinct brown midopercular stripe. Middorsal stripe one-fourth scale wide, extending from nape to dorsal part of caudal peduncle. Pigments on posterior edge of scales distinct and present on up to three longitudinal scale rows on dorsolateral portion of body. Subopercle and pectoral axillary lobe with concentration of melanophores imparting brown appearance. Patch of pigments on scale pocket restricted to pore-bearing scales of laterosensory canal system between pectoral- and anal-fin origins, and in a few specimens on row immediately above it. Pigmentation most intense along anterior portion of lateral line, decreasing gradually in intensity posteriorly. In some specimens, additional pigments on scales of lateral line row forming a faint stripe. Brown midlateral stripe prominent, slightly more intense posteriorly, of approximately oneand-a-half scales width throughout its length, with very discrete and darker upper and lower edges. Stripe extending from behind pectoral girdle to tip of hypural plate. Dorsolateral stripe conspicuous and dark brown or blackish anteriorly, becoming less distinct and paler posteriorly; lower edge of stripe and of dorsal background pigmentation very discrete. Light area between midlateral and supralateral stripes almost totally devoid of pigments, of approximately half-scale width. Posterior extremity of axial streak overlapping midlateral stripe; extending forward along its upper edge until under dorsal-fin base and then for 3–4 scales in light area. Supraanal pigmentation originating slightly anterior to anal-fin origin, terminating at base of posteriormost anal-fin ray. Subpeduncular pigmentation present. Pectoral, dorsal, pelvic and anal fins hyaline, with scattered melanophores on rays. Caudal fin hyaline, with a diffuse brownish patch of pigments on proximal part of 4-5 outermost principal rays of each lobe; a very narrow black margin along posterior edge present in some individuals.

Coloration in life similar, with dark gray to black replacing brown coloration on dorsal and dorsolateral surfaces of head and body, reflective yellowish or greenish coloration on light longitudinal area; diffuse pigmentation along fin rays of pectoral, dorsal, pelvic and anal fins more prominent. Caudal fin carmine red, with very thin gray or black posterior margin ( Fig. 2 b).

Distribution. Rasbora tornieri is known from the Mekong River drainage in Cambodia, as well as river drainages in the Malay Peninsula (from the Perak River drainage, according to Brittan, 1954), Sumatra (from the Siak River drainage southwards to the Musi River drainage) and Borneo (recorded from the Belait River drainage southwards and westwards to the Sambas River drainage; it possibly occurs in other drainages eastwards).

Remarks. The R. tornieri figured by Rainboth (1996: pl. 6) is R. aurotaenia .

Discussion

Bleeker (1850: 14) described R. dusonensis from Banjarmasin on the basis of a single specimen 115 mm TL. He described it as having, among others, a green caudal fin with a blackish posterior margin. This is clearly illustrated in the Atlas (Bleeker, 1863–64: pl. 120), but this figure does not show the holotype. Figures in Bleeker's Atlas are natural size and this specimen is 130 mm SL, which is too large to be the holotype. We have examined material from Banjarmasin (ZRC 40028) and the Barito River drainage (ZRC 38866, ZRC 53468) in agreement with Bleeker's figure and description in both coloration and morphometry (and in disagreement with Brittan's (1954: 122) description of R. dusonensis ). The holotype of R. dusonensis could not be borrowed for direct comparison.

Rasbora tornieri was described from an unspecified location in “Central Sumatra” by Ahl (1922). The collector, Max Moszkowski, travelled in the upper and middle parts of the Rokan Kanan, Rokan Kiri and Siak drainages ("Sultanate of Siak" [=the modern day regency (kabupaten) of Siak in Riau Province, Sumatra] and the "Rokan states"; Moszkowski, 1909a–b: maps). The type locality can thus be restricted to the Rokan and Siak drainages.

Brittan (1954) misidentified material referable to R. tornieri as R. dusonensis (see Kottelat, 1991), at the same time considering R. tornieri a junior synonym of R. cephalotaenia . After examining the syntypes of R. tornieri , he (1972: unnumbered page between pp. 192–193, in the addendum of the reprint of the original 1954 edition) concluded that they are “examples of R. dusonensis , almost perfectly resembling fig. 26, p. 123 [of Brittan, 1954]”. The confusion was exacerbated by Alfred (1963: 130), who examined the holotype of R. dusonensis and concluded that it was conspecific with R. myersi . The fact that the holotype of R. dusonensis is in poor condition and that “[o]nly a weak reticulate colouration is visible” may have prompted Alfred to synonymize R. myersi with R. dusonensis . This led to Kottelat's (1991) usage of R. dusonensis for the large plain gray species then known as R. myersi . However, we note that R. myersi is a distinctly different species with the dorsohypural distance equal to or slightly less than the distance between the dorsal-fin origin and the posterior orbital margin (vs. equal to the distance between the dorsal-fin origin to the middle of the orbit), fewer scale rows between the lateral line and the midventral row in front of the pelvic fins (2 vs. 3) and with a much less distinct and contrasting dark lateral stripe (compare Figs. 1 and 3 ). Although we were unable to examine the holotype of R. dusonensis , we note that the diagnostic characters of R. myersi by (e.g.) Brittan (1954) (absence of a distinct dark lateral stripe and caudal fin without black margin, or with only a blackish edge) are explicitly contradicted by the original description of R. dusonensis , thus ruling out the possibility of their conspecificity.

Kottelat (1991) examined the type series of R. tornieri , and designated and illustrated the lectotype (ZMB 20542). It has all the characters that we consider here as diagnostic for the species.

Both R. dusonensis and R. tornieri belong to the R. argyrotaenia group (sensu Brittan, 1954), which is unlikely to be monophyletic (Liao et al., 2009), but is used here for easier comparison among congeners. Members of this group are characterized by 14 circumpeduncular scale rows, the dorsohypural distance equal to or slightly less than the distance between the dorsal-fin origin and the posterior orbital margin, 1 or 1½ scale rows between the lateral line and the origin of the pelvic fin, and a continuous dark midlateral stripe from the opercle to the base of the caudal fin (Kottelat, 2012). Species in the R. argyrotaenia group include: R. argyrotaenia , R. aurotaenia , R. borneensis , R. everetti , R. laticlavia , R. leptosoma , R. myersi , R. philippina , R. rheophila , R. septentrionalis , and R. vaillantii . Both R. dusonensis and R. tornieri can be distinguished from congeners in the R. argyrotaenia group by the color pattern on the caudal fin in life (see diagnoses), except R. aurotaenia ; additional distinguishing characters are highlighted below.

Among the species of the R. argyrotaenia group, R. aurotaenia is the only other species with a brightly coloured caudal fin. Like R. dusonensis , the caudal fin is bright yellow with a conspicuous black poterior margin in life. Rasbora dusonensis is distinguished fom R. aurotaenia by having a subpeduncular stripe (vs. absent), the midlateral and supralateral stripes with discrete edges and sharply contrasted, and the light area between them almost totally devoid of pigments (vs. stripes with indistinct edges and light area partly covered by pigments), a shorter pelvic axillary scale (about one-fifth of length of fin vs. one-third), and a more slender body (depth 4.0–4.8 times in SL vs. 3.7–4.0).

The identity of R. argyrotaenia awaits further clarification (Kottelat, 2012); it was originally described from Java. Besides the striking colour differences mentioned above, both R. dusonensis and R. tornieri differ from Javanese populations identified as R. argyrotaenia in having the pectoral fin reaching (vs. not reaching) the pelvicfin origin. Both R. dusonensis and R. tornieri are further distinguished from R. borneensis in having a longer head (3.4–4.0 times in SL vs. 4.2–4.5) and fewer predorsal scales (13–14 vs. 15–16), from R. everetti in having the dorsohypural distance equal to or slightly less than the distance between the dorsal-fin origin and the posterior orbital margin (vs. equal to distance between the dorsal-fin origin and a point between the nostril and the anterior orbital margin) and fewer vertebrae (32–34 vs. 36–38), and from R. laticlavia in having more predorsal scales (13–14 vs. 11–12). Rasbora dusonensis and R. tornieri further differ from R. leptosoma in having a longer head (3.4–4.0 times in SL vs. 4.5–4.6), from R. myersi in having the dorsohypural distance equal to or slightly less than the distance between the dorsal-fin origin and the posterior orbital margin (vs. equal to the distance between the dorsal-fin origin to the middle of the orbit), fewer scale rows between the lateral line and the midventral row in front of the pelvic fins (2 vs. 3) and a much less distinct and contrasting dark lateral stripe (compare Figs. 1 and 3 ), and from R. philippina in having the dorsohypural distance equal to or slightly less than the distance between the dorsal-fin origin and the posterior orbital margin (vs. equal to distance between the dorsal-fin origin and a point slightly posterior to the nostril) and a more slender body (depth 3.8–4.5 times in SL vs. 3.1–3.8). Both R. dusonensis and R. tornieri are further distinguished from R. rheophila in having the dorsohypural distance equal to or slightly less than the distance between the dorsal-fin origin and the posterior orbital margin (vs. equal to the distance between the dorsal-fin origin and a point anterior to the nostril), fewer lateral-line scales (27–31+2–3 vs. 31–34+2–3) and vertebrae (32–34 vs. 36–38), from R. septentrionalis in lacking (vs. having) a distinct dark spot at the base of the median caudal-fin rays, and from R. vaillantii in having the dorsohypural distance equal to or slightly less than the distance between the dorsal-fin origin and the posterior orbital margin (vs. equal to the distance between the dorsal-fin origin to the middle of the orbit).

Although both R. dusonensis and R. tornieri were collected syntopically, we have not been able to observe whether they form mixed schools. Even though the two species can be found syntopically, we note that R. dusonensis is more frequently seen in large rivers with murky water and R. tornieri in black water.

Figures

FIGURE 2. Live coloration of: a. Rasbora dusonensis, ZRC 53470, 84.4 mm SL; b. Rasbora tornieri, ZRC ZRC 53469, 73.8 mm SL; both from Sumatra: Sungai Gelam. Figures not to scale.

FIGURE 3. Rasbora myersi, CMK 6960, 58.6 mm SL: Borneo: Danau Temuan, a shallow blackwater lake near Nanga Embaluh.

FIGURE 1. a. Rasbora dusonensis, ZRC 53470, 70.0 mm SL; b. Rasbora tornieri, ZRC 53469, 73.8 mm SL; both from Sumatra: Sungai Gelam. Figures not to scale.