Danio aesculapii, Kullander, Sven O. & Fang, Fang, 2009

Kullander, Sven O. & Fang, Fang, 2009, Danio aesculapii, a new species of danio from south-western Myanmar (Teleostei: Cyprinidae), Zootaxa 2164, pp. 41-48 : 42-44

Danio aesculapii , new species

( Fig. 2 )

Holotype. NRM 44490, 22.5 mm SL; Myanmar: Rakhine State: Thandwe: Kananmae Chaung, near Leldee village, by foot 45 min from Gwechaung village at km 18 on road Thandwe–Taunggok, 18°35'39''N 94°22'45''E; 20 Mar 1998, S. O. Kullander & R. Britz (SOK-98-007).

Paratypes. All from Myanmar, Rakhine State. NRM 40826, 31, 14.7–22.3 mm SL; same data as holotype. — NRM 40804, 38, 17.1–23.7 mm SL; Thandwe: Kamyit Chaung near Paukdu village, 18°15'57''N 94°30'03''E; 19 Mar 1998, S. O. Kullander & R. Britz (SOK-98-005). — NRM 40812, 78, 15.7–21.3 mm SL; NRM 41269, 5, 17.7–24.4 mm SL; NRM 44907, 19, 19.0– 21.1 mm SL; NRM 45662, 1, 22.1 mm SL; Thandwe: Thandwe River drainage: Nan Chaung, a stream at 3 km on road from Thandwe (market) to Ngapali, 18°27'08''N 94°20'55''E; 20 Mar 1998, S. O. Kullander & R. Britz (SOK-98-006). — NRM 40851, 3, 18.6–21.7 mm SL; Thade River drainage: Taunggok, Yan Khaw Chaung, ca 4 km on logging road from Gwetauk village, 23 km on road Taunggok–Pyay, 18°47'48"N 94°21'46"E; 21 Mar 1998, S. O.Kullander & R. Britz (SOK-98-010). — BMNH 2009.5.5.19. 1, 22.7 mm SL; Kaladan River delta: Chaung Gyi bridge in Myay Pon township, 20°08'05''N 93°27'06''E; 1 Apr 2007, R. Britz & J. Maclaine. — BMNH 2009.5.5.1–18, 18, 23.4–28.6 mm SL; Kyeintali River drainage: Kyeintali Chaung; Mar 2006, U Tin Win et al.

Non-types. NRM 52338, 1, 29.6 mm SL; NRM 52341, 25.9 mm SL; Aquarium import; 16 Aug 2005, M. Håkansson. — NRM 52539, 1, 26.0 mm SL; NRM 52542, 24.4 mm SL; Aquarium import; 9 Nov 2005.

Diagnosis. Different from all other species of Danio by colour pattern comprising 6–7 brown vertical bars anteriorly on side and two horizontal rows of small brown spots posteriorly, absence of D stripe, and absence of dark stripes on caudal fin; similar to D. kerri and D. erythromicron in possession of 12 circumpeduncular scale rows vs. 14 in D. dangila and 10 in other species of Danio ; by possession of 6 branched dorsal fin rays, vs. 7–8 in other species of Danio .

Description. Measurements and counts were taken from ten specimens, 20.0– 22.5 mm SL (Table 1), supplemented by counts from additional X-radiographed specimens. The holotype is well preserved but most other specimens have lost scales. General body features and pigmentation are illustrated in Figs. 1–2 . External sexual dimorphism restricted to slightly rounder abdomen and slightly less developed tubercle field on lower jaw in females,.

Body compressed, elongate. Head compressed, slightly deeper than wide. Snout short, rounded, shorter than eye diameter. Mouth terminal, obliquely directed upwards. Small bony knob at dentary symphysis. Maxilla reaching to below anterior margin of orbit; premaxillary ascending processes not reaching to vertical from anterior margin of orbit. Lower jaw projecting slightly beyond upper jaw, ending anteriorly at horizontal through middle of eye. Lower jaw with anterior fleshy lateral lobe beset with small conical tubercles; anteriorly on lower jaw several conical tubercles; a row of conical tubercles along lateral margin of dentary posterior to lateral lobe. Tuberculation variably developed, stronger in males. Maxillary barbels about double length of rostral barbels, ending at insertion of pectoral-fin base, except in 24.4 mm specimen (NRM 41269) in which extending posterior to pectoral-fin base. Rostral barbels reaching to posterior margin of orbit.

Squamation incomplete in many specimens due to abrasion. Lateral line short, with 4 (1), 5 (7) scales; scales in lateral row 28 (4), 29 (3), counting scale pockets and remaining scales. Median predorsal scales 15 (2), 16 (4), 17 (1). Lateral scale rows passing between dorsal and pelvic fins 7 (8). Circumpeduncular scale rows 12 (8). A row of scales along anal-fin base.

D. ii.6 ½ (19); A. iii.10 ½ (1), iii.11 ½ (11), iii.12 ½ (6); P. i.10 (2), i.11 (8); V. i.7 (10). Dorsal fin inserted at highest point of dorsum, at about 3/5 distance from head to caudal-fin base, slightly anterior to vertical from anal-fin origin. Pectoral-fin insertion at about vertical through posterior margin of osseous opercle. Pectoralfin rays long, extending to pelvic-fin origin. Pectoral-fin axial lobe well developed. Pelvic-fin origin situated at about middle of body, anterior to dorsal-fin origin; pelvic fin reaching to anal-fin origin. Pelvic axillary scale present. Caudal fin forked, lobes of about equal length.

Vertebrae 15+17=32 (6), 15+18=33 (4), 16+17=33 (4), 17+17=34 (1).

Colouration in preservative. Whitish ground colour. Dorsal scales sparsely pigmented, slightly darker at rim; except dark brown predorsal midline, and dark brown dorsal midline of caudal peduncle. Horizontal stripes absent. A series of 6–7 (usually 6) short light brown vertical bars along middle of side anterior to vertical from anal-fin base, continued posteriorly by two parallel rows of alternating small blotches of the same colour, lower row comprising 5–7 (usually 6) blotches and running along midline, upper row coalescing with dorsal pigmentation. Lightly pigmented above anal-fin base and along caudal peduncle below narrow unpigmented line separating row of blotches. Pigment absent from interspaces between blotches and bars, but bars and dorsal blotches grading dorsally into diffuse dorsal pigmentation. Dorsal fin hyaline without dark markings, except that margins of rays may be dark. Caudal fin hyaline, without markings. Pectoral and pelvic fins hyaline with scattered pigment. Anal fin hyaline, with distinct dark A stripe across middle and less densely pigmented broad dark band distally on fin.

Molecular data. Nucleotide sequences of the mitochondrial cytochrome b gene and a fragment of the nuclear rhodopsin gene were obtained from a specimen from the aquarium trade (NRM 52542) and reported by Fang et al. (2009), with GenBank accession numbers EU241365 and EU241430 (as Danio sp. “snakeskin”).

Etymology. Genitive of Aesculapius (Latin form of Asklepios, Ἀσκληπɩός), Ancient Greek god of medicine, equipped with a staff with one or two snakes wrapped around it; a reference to the snakeskin pattern attributed to this species.

Geographical distribution and habitat. Known only from small steams on the western slope of the Rakhine Yoma, near Thandwe ( Fig. 3 ), Kyeintali and Sittwe. The type locality ( Fig. 4 ) was a small stream flowing out of the forest into cultivations, at most 3 m wide, and about 30 cm deep. The water was clear with only slight current and, at the collecting site, concentrated in four pools. There was no aquatic vegetation and the bottom consisted of pebbles, rock, and gravel. Associated fauna included Anguilla sp. ( Anguillidae ), Aplocheilus panchax (Hamilton) (Aplocheilidae) , Batasio elongatus Ng and Olyra burmanica Day (Bagridae) , Schistura sp. ( Nemacheilidae ), Channa sp. ( Channidae ), Lepidocephalichthys berdmorei (Blyth) and Pangio pangia (Hamilton) (Cobitidae) , Danio sp. aff. dangila , Devario sp., Garra flavatra Kullander & Fang , G. vittatula Kullander & Fang , Puntius binduchitra (Hora) , two species of Puntius Hamilton , Rasbora daniconius (Hamilton) , R. rasbora (Hamilton) (Cyprinidae) , Eugnathogobius siamensis (Fowler) and Sicyopterus fasciatus (Day) (Gobiidae) , Mastacembelus armatus (La Cepède) (Mastacembelidae) , and Pterocryptis berdmorei (Blyth) (Siluridae) . Other localities near Thandwe included one stagnant pool, remnant of a small river, Nan Chaung, at low water level, with leaf litter and sand for bottom substrate, the other localities being small forest streams with rocky bottoms. The associated fauna varied slightly, but was essentially dominated by Rasbora , except in Yan Khaw Chaung where an undescribed large species of Devario was the most abundant species.

Figures

FIGURE 1. Danio aesculapii, drawing from Hora (1937: fig. 2), based on a 33 mm TL specimen from Thandwe.

FIGURE 2. Danio aesculapii, holotype, NRM 44490, male, 22.5 mm SL; Myanmar: Rakhine State: Thandwe: Kananmae Chaung, near Leldee village.

FIGURE 3. Danio aesculapii. Collecting sites. The Kyeintali locality at the extreme south is approximate.

FIGURE 4. Danio aesculapii. Type locality. Myanmar: Rakhine State: Thandwe: Kananmae Chaung, near Leldee village. 20 March 1998.