Betta dennisyongi, Hui, 2013

Hui, Tan Heok, 2013, The Identity Of Betta Rubra (Teleostei: Osphronemidae) Revisited, With Description Of A New Species From Sumatra, Indonesia, Raffles Bulletin of Zoology 61 (1), pp. 323-330 : 326-329

Betta dennisyongi , new species

( Figs. 1E,F , 7A,B , 8A,B )

Betta rubra (non-Perugia) – Tan & Ng, 2005b: 119, Figs. 1a,b (part); Tan, 2008: 6 (part); Schindler & van der Voort, 2012: 23.

Material examined. — ( all from Aceh Province) – Holotype: MZB 17207, 27.4 mm SL male; Sumatra: Aceh: Kabupaten Nagan Raya: Lamie, Alue Rayeuk , stream along road Meulaboh-Blangpidie ; brown water stream at rubber estate (57 m asl, pH 6.1); T. Sim et al., 16 Apr.2009.

Paratypes – MZB 17208, 4 ex., 22.0– 23.5 mm SL ; ZRC 53990, 19 ex., 10.1–28.0 mm SL; same locality as holotype . ZRC 53991, 25 ex., 13.2–33.0 mm SL; Sumatra: Aceh: Kabupaten Aceh Barat Daya: Alue Labi, stream through oil palm estate along road Meulaboh-Blangpidie ; T. Sim et al., 16 Apr.2009 . ZRC 53995, 7 ex., 19.0– 33.5 mm SL; CMK 23281, 4 ex., 27.9–31.4 mm SL; Sumatra: Aceh, Aceh Barat , stream flowing through padi fields at Cot Mane, Kreung Babah Rot drainage; H. H. Ng et al., 2 Jun.2010 .

m asl, pH 7.0); T. Sim et al., 18 Apr.2009. ZRC 50871, 2 ex. ,

25.6–29.5 mm SL; Aceh Selatan area; H. Ishizu, Feb.2007. MZB 4784 , 3 ex., 23.4–35.0 mm SL ; ZRC 42497, 2 ex., 33.4–35.4 mm SL; Sumatra: Aceh Barat, Alur Sungai Iamueselatan; H. B. Munaf & M. Toha, 13 Dec.1982 . ZRC 51378, 7 ex., 24.1–28.3 mm SL; Sumatra: southern Aceh, trade material; Ishizu, Feb.2008 .

Diagnosis. — Betta dennisyongi can be distinguished from B. rubra by the following suite of characters: a continuous black postorbital stripe extending up to opercle edge (vs. Non-type material examined. — (all from Aceh Province) – ZRC 53992, 2 ex., 19.2–29.4 mm SL; Sumatra: Aceh: Kabupaten Aceh Singkil: Trumon , hill stream along road Subulussalam-Singkil (11

interrupted stripe); broad suborbital stripe below eye forming a triangular black mark (4–5 scale rows wide, vs. 2–3); less intense body colouration with wider interspaces between the black body bars; fewer anal-fin rays (mode 25, vs. 27); a greater number of subdorsal scales (6–7, vs. 5–5 ½); a greater number of lateral scales (mode 31, vs. 30); a greater number of vertebrae (mode 30, vs. 29); longer dorsal-fin base length (13.0–18.4, vs. 11.0–13.4% SL); and smaller maximum size (35.4 vs. 42.1 mm SL).

Description. — General appearance as illustrated in Figs. 7A,B , 8A,B ; meristic and morphometric data of B. dennisyongi are listed in Table 1. Body relatively slender (body depth 23.1–28.5% SL), head relatively short (head length 29.9–37.1% SL). Dorsal and anal fins pointed, caudal fin rounded with extended median rays and interradial membrane; dorsal fin placed relatively far back (predorsal length 64.0–69.2% SL); anal-fin base length about half of standard length (47.2–58.4% SL); pelvic fin falcate with first ray long and filamentous (28.0–40.6% SL); pectoral fin rounded. Vertebral count: 9–11 + 19–20 = 29–30 (mode = 30, n = 20). Maximum size: 35.4 mm SL.

Preserved colouration. — See Fig. 7A,B for general appearance. Dorsum of body dark brown, lateral cream with reddish patches, ventrum cream. Dorsum of head brown with black spots. Mouth with lower lip black. Distinct pre- and postorbital black stripes on head, a continuous postorbital black stripe from posterior of eye to opercle edge, posterior half of stripe deeper. Black chin-bar/suborbital stripe present, forming a triangular dark brown to black mark below eye; as wide as or wider than eye diameter. Opercular region brown to cream. Male body with 5–8 irregularly spaced blackish vertical bars, restricted to midsection and lower half of body; bars prominent on anterior three-quarters of body. Female – body with dark brown stripe nearly continuous to caudal fin base, interrupted by caudal peduncle black spot. Caudal peduncle spot faint. Fins light reddish-brown. Dorsal, caudal and anal fins without transverse bars on interradial membrane, with hyaline edge. Pectoral fin hyaline, base blackish. Pelvic fin reddish.

Live colouration. — See Fig. 8A,B for general appearance. Basal body colour reddish to brownish. Dorsum darker than ventrum. Dorsum of head with dark brown to black spots. Mouth with lower lip black. Lower half of iris of eye bright bluish. Head and opercle pattern as above; posterior half of opercle reddish or yellowish-brown with gold and bluish iridescence; opercle edge brighter red. Body with irregularly spaced blackish vertical 5–8 bars, restricted to lower half of body. Fins reddish. Dorsal caudal and anal fins with bright bluish-green edge; base of anal fin with bluish iridescence. Pectoral fin base with an iridescent bluish-green spot/crescent. Pelvic fin reddish with bluish flush and blue tip.

Field notes. — It appears that Betta dennisyongi occupies lowland hillstream and acid water swamp habitats. It occurs in clear to brown-water habitats, from secondary forest to plantation and farmland environments. A typical acid-water habitat is illustrated in Fig. 9 , in which remnant swamp forest vegetation still persisted (in the form of the aroid Lasia with the larger upward-pointing arrow- shaped leaves). Syntopic fish species included: Osteochilus jeruk , Rasbora jacobsoni , R. kluetensis (Cyprinidae) ; Nemacheilus tuberigum (Nemacheilidae) ; Mystus punctifer (Bagridae) ; and Ompok brevirictus , Kryptopterus piperatus (Siluridae) .

Distribution. — Betta dennisyongi is currently known only from west coast of central Aceh, from Meulaboh to lowland hill streams before Singkil ( Fig. 6 ).

Etymology. — This species is named for Dennis Yong Ghong Chong, a distinguished and knowledgeable naturalist well experienced in many facets of tropical Southeast Asian fauna and flora with an avid interest in labyrinth fishes. He has accompanied the author on many trips and shared many interesting stories, tips and gastronomic delights.

Remarks. — Since the rediscovery of Betta rubra in 2007–2008, this species had been sporadically available in the ornamental fish trade. Breeding reports of this species were available showing it to be a paternal oral brooder. A casual image search through the world wide web has revealed many websites with photographs of ‘ B. rubra ’, either on breeding reports or sales. Many of these images posted as B. rubra actually show B. dennisyongi , judging from the opercular pattern; although some do illustrate true B. rubra . A series of B. rubra specimens from the trade was received in 2008 by kind donation through Ishizu (ZRC 51378, ZRC 54000), which based upon present information, turn out to be a mix of both species. It appears that this mix could be a result of: i) mixing of specimens obtained from different locations either by the collectors themselves or at the middle-man level; ii) possible syntopic populations in probably human-disturbed habitats.

There are two lots of specimens (ZRC 53989 and ZRC 53992) obtained from Aceh Singkil region; but each lot belonging to a different species. The two habitats are very different and could reflect habitat segregation or a natural boundary/extent of distribution of the two taxa. The series ZRC 53989 identified as B. rubra was obtained from peat swamp habitat (presently extirpated due to habitat modification for oil palm plantations), with deep peat deposits and typical black water (pH 5.5). The series ZRC 53992 identified as B. dennisyongi was obtained from a relatively fast flowing clear water (pH 7.0) lowland hill stream, with a sandy bottom and steep clay banks. The fish specimens were obtained from submerged leaf litter and found not to be abundant. In comparison, the main type series ZRC 53990 ( B. dennisyongi ) was obtained from submerged leaf litter and bank vegetation from a brownwater habitat (pH 6.0) which had slow flowing water over a mud-clay substratum.

Figures

Fig. 1. Comparison of lateral head and opercle pattern, left side with photograph, right side with schematic drawing. A, B, Betta rubra, MSNG 13019, lectotype, 28.6 mm SL; C, D, Betta rubra, ZRC 53989, 34.0 mm SL male; E, F, Betta dennisyongi, MZB 17207, holotype, 27.4 mm SL male.

Fig. 7. Betta dennisyongi: A, MZB 17207, holotype, 27.4 mm SL, male; B, ZRC 53990, paratype, 30.0 mm SL female; central Aceh.

Fig. 8. Betta dennisyongi: A, ZRC 50871, 29.5 mm SL male, colouration in life; B, same specimen, acclimatised colouration.

Fig. 9. Type locality of Betta dennisyongi, remnant swamp-forest habitat in central Aceh (2009).

Fig. 6. Map of Sumatra showing distribution of Betta rubra (round symbols) and B. dennisyongi (square symbols).