Rasbora pycnopeza, Wilkinson & Hui, 2018

Wilkinson, Clare L. & Hui, Tan Heok, 2018, Fishes of the Brantian drainage, Sabah, Malaysia, with description of a new Rasbora species (Teleostei: Cyprinidae), Raffles Bulletin of Zoology 66, pp. 595-609 : 605-607

Rasbora pycnopeza , new species

( Figs. 3–5 )

Rasbora sumatrana (non-Bleeker) – Brittan, 1954: 56 (part), fig. 7; Inger & Chin, 1962: 56, fig. 23; Kottelat et al., 1993: 65 (part); Martin-Smith & Tan, 1998: 584; Chin, 2002: S-12, fig. S7.

Rasbora cf. sumatrana – Tan, 2013: no. 9.

Material examined. Holotype. ZRC 56719, 87.8 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan , 120 m stream ( SAFE project experimental area); Wilkinson CL, July 2015.

Paratypes. ZRC 56720, 1 ex., 74.2 mm SL; same locality data as holotype . – ZRC 56722, 2 ex., 90.0– 104.1 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan , 30 m buffer stream ( SAFE project experimental area); Wilkinson CL, 21 June 2016 . – ZRC 56721, 3 ex., 70.3–80.4 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan , 30 m stream ( SAFE project experimental area); Wilkinson CL, 23 April 2016 . – ZRC 56730, 3 ex., 74.2–88.1 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan , 30 m buffer stream ( SAFE project experimental area); Wilkinson CL et al., 23 April 2017 . – ZRC 56723, 1 ex., 78.3 mm SL, Malaysia: Sabah: Brantian drainage near Kalabakan, Virgin Jungle Reserve stream ( SAFE project experimental area); Wilkinson CL et al., 23 June 2016 . – ZRC 56724, 3 ex., 80.7–100.4 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan , 0 m buffer stream ( SAFE project experimental area); Wilkinson CL, July 2015 . – ZRC 56725, 2 ex., 88.3–102.7 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan , 0 m buffer stream ( SAFE project experimental area); Wilkinson CL, July 2015 . – ZRC 56728, 6 ex., 63.0– 75.5 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan, Logged Forest Edge stream ( SAFE project experimental area); Wilkinson CL, 4 May 2015 . – ZRC 56731, 1 ex., 77.8 mm SL ; ZRC 56730, 3 ex., 74.2–88.1 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan, Logged Forest Edge stream ( SAFE project experimental area); Wilkinson CL et al., 24 April 2017 . – ZRC 56729, 2 ex., 64.8–71.0 mm SL; Malaysia: Sabah: Brantian drainage near Kalabakan, Virgin Forest Reserve stream ( SAFE project experimental area); Wilkinson CL, 7 May 2015 . – ZRC 56726, 1 ex., 73.3 mm SL; Malaysia: Sabah: Segama drainage near Danum Valley field centre, West Stream ; Wilkinson CL, 1 March 2016 . – ZRC 56727, 2 ex., 65.5–65.8 mm SL; Malaysia: Sabah: Segama drainage near Danum Valley field centre, Tembaling Stream; Wilkinson CL, 10 March 2016 .

Diagnosis. Rasbora pycnopeza is distinguished from its congeners in Southeast Asia by the following combination of characters: size up to at least 104mm (SL) and its distinctive caudal-fin colour pattern consisting of a thick distal black margin, covering ⅓ to ½ of upper and lower fin lobes; a distinct thin black lateral stripe starting 5–6 scales posterior to opercle edge to base of caudal-fin; and a black stripe at supraanal region covering entire anal-fin base. When live or freshly preserved, dorsal fin is orange, pectoral, pelvic and anal fins are yellow, and the caudal fin is faintly yellow with a distinct black margin, the upper and lower caudal-fin lobes with up to a third or half black.

Description. General appearance in Figs. 3 , 4 and 5 ; morphometric data of holotype and 20 paratypes in Table s3. Streamlined, slender body, deepest at dorsal-fin origin, tapering towards the caudal peduncle. Snout pointed, symphysal knob present. Dorsal fin with 1 simple and 7½ branched rays; origin above lateral line scale 10–13. Pectoral fin slightly falcate, with 15 rays, not reaching pelvic-fin origin. Pelvic fin slightly pointed, with 9 rays, reaching about anus; axillary scale present. Anal fin with 1 simple and 5½ branched rays. Caudal peduncle 1.6–2.0 times longer than deep, and caudal fin length appears large (TL – SL) is 210.1–279.5 % caudal peduncle depth, with 8–9 + 10 principle rays, 7–8 + 9 branched; deeply forked. Lateral line complete, perforating 28–33 + 1 scales (29 + 1 modally) along lateral line, 10–12 predorsal scales (12 modally), ½4/1/1½ scales in transverse, ½3/1/1½ scales in transverse on caudal peduncle, 1 scale between lateral line and pelvic-fin origin. Vertebral count consist of 15–16 abdominal + 16–17 caudal, total of 31–33 (mode 33, n = 21).

Colouration. See figure of preserved specimen ( Fig. 5 ). Body dark brown on the dorsum, fading to yellowish brown on the lateral and cream on the ventrum. Dorsum has a fine reticulated pattern due to diffused melanophores along posterior edge of body scales, darker and more defined dorsally and paler ventrally only extending below midlateral stripe anteriorly. A black midlateral stripe originating 5–6 lateral scales posterior to opercle edge to caudal-fin base. Black lateral stripe most defined in central to posterior half (up to half a scale deep), and ends in a widened but faint elongated triangular blotch at caudal-fin base, not continuing on median caudal rays. A conspicuous black, elongated supra-anal streak, extending the length of the anal-fin base wider anterior of anal fin. Rest of fins hyaline, without black margins; except the caudal fin, which has a distinct black posterior margin covering ⅓ to ½ of the fin.

In life ( Figs. 3 , 4 ; Martin-Smith & Tan, 1998: 584): Body silvery, lateral line dark blue; supra-anal streak black, conspicuous; orange dorsal fin; yellow pectoral, pelvic and anal fins; yellow caudal fin with a distinct black posterior margin covering ⅓ to ½ of the fin.

Distribution. Rasbora pycnopeza is currently recorded from Kinabatangan (plus the Kuamut sub-basin draining from Danum Valley), Segama, Tawau Hills, and Kalabakan basins in western Sabah. Inger & Chin (1962: 57) also lists the following locations (but material from these locations have not been examined except marked with *): Jesselton District – Menggatal; Kinbatangan District – Sungei Gaja, Sungei Kretam Kechil, Deramakot; Sandakan District – Sungei Gum Gum, Sungei Kabili*, Sandakan, Sungei Sapagaya, Sepilok Forest Reserve*; Semporna District – Sungei Mapat; Tawau District – Selimpopon River, Sungei Tawau*, Sungei Balung, Sungei Kinabutan, Sungei Tawan, Sungei Magam, Sungei Brantian; Tuaran District – Kiulu. Chin (2002: SC-12) includes Ranau District – Ranau, Sungei Liwagu*. It is expected to occur in the majority of these drainages in Sabah, as well as in the northernmost part of Kalimantan Timur (for example in Sembakung drainage, which originates in Sabah).

Etymology. From the conjugation of the Greek pyknos, meaning thick, dense; and Greek peza, meaning border, edge; in allusion to the thick black border of the caudal fin. Used as a noun in apposition.

Remarks. Rasbora pycnopeza belongs to the Rasbora sumatrana-elegans complex described by Brittan (1954: 53), which then included the following valid species on Borneo: R. sumatrana , R. volzii , and R. elegans . Brittan diagnosed this complex by a combination of the following: 12 rows of scales around the caudal peduncle, a complete lateral line, the dorsal-fin origin above or behind the posterior extremity of the pelvic-fin base, the presence of a poorly contrasted mid-lateral stripe (sometimes missing), the axial streak ending in a precaudal spot in some species, or with a conspicuous dark blotch in the middle of the side in some species. These complexes were constructed by Brittan based on the similarity of general appearance, but are now outdated by the description of numerous additional species since 1954 and species being re-described. These complexes are nevertheless a convenient tool to ease comparison of species.

Among the species originally included in the R. sumatranaelegans complex, the status of R. sumatrana has been discussed by Tan & Kottelat (2009) and Kottelat (2005). As recognised by Brittan (1954), R. sumatrana was distinguished by having a black midlateral stripe ending in a diamond shaped blotch at the base of the caudal fin. Rasbora sumatrana sensu stricto is restricted to the highlands of western Sumatra (Tan & Kottelat, 2009). Its whole geographic range is not yet known precisely; there is also a likelihood that several species are presently confused under that name. The fishes earlier identified as R. sumatrana from Borneo by Brittan (1954) are now re-identified as R. hosii and R. calliura (fide Tan & Kottelat, 2009). In Borneo, there are several described taxa which we feel maybe confused with R. pycnopeza . These are R. atranus , R. cryptica , R. hubbsi , R. tornieri , and R. rheophila .

Rasbora pycnopeza is distinguished from R. rheophila by snout shape (pointed vs. rounded); snout length (28.3–34.2 % HL, vs. 26.3 %); shortened and conspicuous lateral stripe starting midway between pectoral and pelvic fins (vs. continuous stripe); fewer circumpeduncular scales (12 vs. 14); fewer lateral scales (28–33 +1 vs. 31 + 2); more anterior placement of dorsal-fin origin (position in relation to lateral scales 10–13 vs. 15); wider extent of pigments along the posterior margin of the caudal-fin lobes (⅓ to ½ of the fin covered, vs. extreme outer margin of upper caudal-fin lobe); and longer head length (22.5–26.7 % SL, vs. 22.9). Tan & Kottelat (2009) concluded that R. hosii is the valid name of the Sarawak R. ‘ sumatrana ’ from the type locality in the Baram River. Rasbora pycnopeza differs from R. hosii by a larger size (total length up to 104 mm, vs. 61–73); shorter predorsal length (49.6–54.6 % SL, vs. 55.4–57.3); less body depth at dorsal-fin origin (22.1–25.9 % SL, vs. 26.4–27.9) giving R. pycnopeza a slimmer appearance; more distinct black streak along whole anal-fin base (vs. a diffused appearance); midlateral black stripe is distinct and sharply contrasted (vs. indistinct and gradually narrowing on the caudal peduncle); extent of pigments along the posterior margin of the caudal-fin lobes (⅓ to ½ of the fin covered, vs. extreme outer margin).

Rasbora pycnopeza is distinguished from R. atranus by a longer body (trunk length 74.1–78.8 % SL, vs. 68.5–74.9); shorter head length (22.5–26.7 % SL, vs. 27.1–30.3); shape of the supraanal stripe (a longitudinal streak along whole anal-fin base, vs. an elliptical to triangular blotch); presence of a conspicuous blackish posterior margin on the caudal-fin lobes (vs. absence); midlateral black stripe clearly marked and gradually narrowing (vs. less sharply contrasted or indistinct and markedly narrowing on the caudal peduncle).

Several other species of Rasbora are present in hill stream habitats in Borneo and these include R. cryptica , R. hubbsi , R. tornieri , R. vaillanti , and R. volzii . These taxa are also compared with R. pycnopeza .

Rasbora pycnopeza is distinguished from R. cryptica by a longer body (trunk length 74.1–78.8 % SL, vs. 72.0–75.1); shorter predorsal length (49.6–54.6 % SL, vs. 54.0–56.2); different caudal fin pattern (thick black margin, covering ⅓ to ½ of caudal-fin lobes, vs. none); a distinct thin black lateral stripe 3-5 scales posterior to opercle edge till base of caudalfin, vs. a thin diffused stripe with a mid-body black blotch and an elongate triangular black blotch at caudal peduncle.

Rasbora pycnopeza lives sympatrically with R. hubbsi in the Kalabakan and Segama drainages. R. pycnopeza is distinguished from R. hubbsi by reaching a greater size (maximum standard length up to 104 mm vs. 41.4–43.9); less body depth at dorsal-fin origin (22.1–25.9 % SL, vs. 26.8–9.2), longer median caudal length (16.3–20.9 % SL, vs. 13.3–16.4), having 12 vs. 14 circumpeduncular scales rows, 1 vs. 2 scale rows between the lateral line and the origin of the pelvic fin, and an distinct midlateral black stripe with an equal intensity along whole length (vs. thick stripe, more intense posteriorly, with an abrupt transition to the much diffused anterior portion).

Rasbora pycnopeza differs from R. tornieri by having fewer circumpeduncular scales rows (12 vs. 14); a different lateral head profile (slightly concave vs. straight); caudal-fin pattern consisting of a thick black margin, covering ⅓ to ½ of caudal-fin lobes (vs. a black margin ¼ to 1/5 of caudal fin); distinct thin black lateral stripe starting 5–6 scales posterior to opercle edge to base of caudal-fin (vs. presence of a broad, dark, sharply defined midlateral stripe, extending from opercle to caudal-fin base and separated from the dark dorsum by a highly contrasting cream longitudinal area); and a distinct black stripe at supraanal region covering entire anal-fin base (vs. none or a faint black streak at supraanl region).

Rasbora pycnopeza differs from R. vaillanti in having a shorter predorsal length (49.6–54.6 % SL, vs. 55.2–58.8); less body depth at dorsal-fin origin (22.1–25.9 % SL, vs. 27.4–32.7), body depth at anus (18.2–22.3 % SL, vs. 21.8– 24.2), and caudal peduncular depth (11.9–13.7 % SL, vs. 13.0–13.8); a conspicuous black streak along anal-fin base, thicker at the anterior end (vs. a less distinct and thinner streak, not extending along the whole length of the anal fin base); and caudal fin with thicker black margin (⅓ to ½ of caudal-fin lobes vs. extreme outer margin).

Rasbora pycnopeza is distinguished from R. volzii by the shape of the black mark above the anal-fin origin (a conspicuous thickened black streak, vs. thin black streak along whole anal-fin base); pointed snout (vs. rounded); the colour of the fins in life (orange/yellow, vs. hyaline); presence of a black distal margin on caudal-fin lobes (vs. absence).

Rasbora pycnopeza can be distinguished from R. calliura by shape of the black mark above the anal-fin origin (a conspicuous thickened black streak, vs. thin and diffused black streak along whole anal-fin base); longer snout (vs. shorter); distinct mid-lateral stripe (vs. indistinct, present on posterior half of body); the colour of the fins in life (orange/ yellow, vs. reddish-orange); caudal fin with black margin (black margin thickened on ⅓ to ½ of caudal-fin lobes, vs. ¼ of caudal fin lobes).

Comparative material. Rasbora atranus : ZRC-51186, 5 ex., 65.3–80.8 mm SL; Borneo : Kalimantan , Mahakam drainage: Barito Utara. – Rasbora calliura: ZRC 56406, 5 ex., 46.7–76.3 mm SL; Borneo : Sarawak: Upper Sarawak basin, Kiri River , Kan River . – Rasbora cryptica : ZRC- 52463, 1 ex., ZRC-52462, 4 ex., 44.3–70.8 mm SL; Borneo : Sarawark : Penrissen foothills near Serian. – Rasbora hosii: ZRC 42725, 5, 61.1–77.3 mm SL; Borneo : Brunei. – Rasbora hubbsi: ZRC , 2 ex., 41.4–43.9 mm SL; Borneo : Sabah: Brantian drainage. – Rasbora rheophila: ZRC 47505, 1 ex., paratype, 68.1 mm SL; Borneo: Sabah: Kota Marudu. – Rasbora sumatrana: ZRC 42289, 5 ex., 42.1–59.5 mm SL; Indonesia: Sumatra: Danau Lingkat. – Rasbora tornieri: ZRC 46077, 2 ex., ZRC 42726, 3 ex., 84.8–111.7 mm SL; Borneo: Sarawak: Miri, & Brunei. – Rasbora vaillanti: ZRC , 5 ex., 54.6–62.4 mm SL; Borneo: Kalimantan: Mahakam drainage: Kota Bungan. – Rasbora volzii: ZRC 47024, 5 ex., ZRC 45627, 1 ex., 59.9–109.8 mm SL; Borneo: Kalimantan: Kayan drainage .

Figures

Fig. 3. Rasbora pycnopeza, new species, live specimen from Tawau, not preserved (photographed by second author in 2008).

Fig. 4. Rasbora pycnopeza, new species, freshly dead specimen from Kalabakan Forest Reserve (photographed by second author in 2011).

Fig. 5. Rasbora pycnopeza, new species, ZRC56719, holotype, 87.8 mm SL (top with black background, bottom with white background), from SAFE 120m stream in Kalabakan Forest Reserve.