Dario tigris, Britz & Kullander & Rüber, 2022

Britz, Ralf, Kullander, Sven & Rüber, Lukas, 2022, Dario tigris and Dario melanogrammus, two new species of miniature chameleon fishes from northern Myanmar (Teleostei: Badidae), Zootaxa 5138 (1), pp. 1-16 : 2-5

Dario tigris , new species

( Figures 1–2 )

Holotype. BMNH 2019.10 .16.100, male, 16.7 mm SL. Myanmar, Kachin State, unnamed mountain stream south of Mogaung ; unknown collector, 2 Feb 2013.

Paratypes. BMNH 2019.10.16.101–130, 29, 11.7–15.5 mm SL; same data as holotype . BMNH 2019.10.16.131– 168, 38, 12.2–18.0 mm SL; same data as holotype . MTD F-40101, 7, 12.4–15.5 mm SL same data as holotype . MTD F-40102, 2, c&s, 12.5–15.2 mm SL; same data as holotype . NRM 44001, 1 , 21.2 mm SL, stream about 1.5 km on road Myitzon-Myitkina , 25º 42´57″N 97º 29´45″E, F. Fang et al., 3 Apr 1997 , NRM 44002, 1 , 18.3 mm SL; ditch marginal to fish ponds about 40 km N of Myitkina, on road to Myitzon 25º 29´00″N 97º 24´51″E; S.O. Kullander & R. Britz , 24 Mar 1998 .

Diagnosis. A small badid species, barely exceeding 20 mm SL, distinguished from all other species of Dario by its unique colour pattern, which consists of a series of eight straight bars, of which in males the first two are ash-grey and the subsequent six are orange-red in life, combined with a series of contrasted small black spots arranged in irregular rows dorsolaterally on the head and nape (vs different colour pattern). It can be further distinguished from the southern Indian species of Dario by fewer vertebrae (24, rarely 25 vs 26–29 in D. urops , D. huli and D. neela ). In addition to its colour pattern, it differs further from its close relative D. hysginon , with which it is recorded to occur syntopically, by fewer dorsal-fin spines (modally 14 vs modally 15) and fewer vertebrae (modally 12+12=24 vs modally 12+13= 25). It differs further from the only other barred Dario species in Myanmar, D. melanogrammus by fewer vertebrae (modally 24 vs modally 26) and dorsal-fin spines (12–13 vs 14–16).

Description. For general appearance see Figs 1–2 ; morphometric data are provided in Table 2 and meristic data in Tables 4–5 . Body elongate, moderately laterally compressed. Predorsal and prepelvic lateral profile convex. Eye situated in anterior half of head, snout short. Mouth supraterminal, directed slightly obliquely upwards with lower jaw projecting. Corner of gape situated in front of anterior margin of eye. Angle of jaws situated at vertical through anterior third of eye. Dorsal profile of body convex, ventral profile straight. Caudal peduncle profile parallel, only slightly attenuated posteriorly. Intraoral teeth present in a marginal row anteriorly on vomer and in a circular posterior patch on parasphenoid, but absent from palatine, basihyal and hypobranchial 3. Teeth also developed on pharyngobranchials 2 and 3 and upper pharyngeal toothplate 4, as well as on ceratobranchial 5. Pharyngobranchial 1 absent. Branchiostegal rays six. Two slender supraneurals in front of first dorsal-fin pterygiophore; first situated between occiput and first neural spine, second between first and second neural spine.

Lateral-line canal pores present only on head, absent from body. Head canal pores comprise: preopercular pores (p1–p6), nasal pores (n1–n2), supraorbital pores (f1–f4), extrascapular pores (ex1–ex3), posttemporal pores (po1– po2), coronalis pore (cor), lachrymal pores (l1, l3); dentary, anguloarticular, and infraorbital pores absent. Scales ctenoid on sides, cycloid on top of head. Tubed lateral-line scales absent. Scales in longitudinal row 23. Scales in transverse row 8. Circumpeduncular scales 16.

Dorsal-fin lappets in males only slightly extending beyond distal tip of fin spines; soft dorsal fin rounded, extending to caudal-fin base in females and beyond in males. Soft anal fin rounded, barely reaching to caudal-fin base in females, slightly beyond caudal-fin base in males. Caudal fin subtruncate. Pectoral fin rounded, with 13 rays, extending to level of third dark bar. Pelvic fin pointed, medial branch of first fin ray and lateral branch of second fin ray extended and forming tip. Pelvic fin sexually dimorphic: stopping short of anterior anal-fin base in females, but extending to first anal-fin spine in males.

Vertebrae 12+12=24 (32), 12+13=25 (5). Dorsal-fin spines XIII+7 (2), XIII+8 (1), XIV+5 (1), XIV+6 (10), XIV +7 (19), XV+5 (2), or XV+6 (2). Anal-fin spines III+7 (22) or III+8 (15). Caudal-fin with 14 principal and 2–3 dorsal and 1–3 ventral procurrent rays: 2+7+7+1 (3), 2+7+7+2 (9), 3+7+7+2 (18), 3+7+7+3 (7).

Colouration in preservative. Background colour on head and body beige. Preorbital, supraorbital and postorbital stripes well developed. A number of distinct, black spots on head and nape between eye and second bar, arranged in several, usually three to four, irregular longitudinal rows. Cheek and opercular area dusky from dense peppering with melanophores. Series of six dark brown double-bar saddles across side, fainter in female, originating from base of dorsal fin and extending ventrally to ventral midline, a sixth bar on anterior caudal peduncle extending between posterior bases of dorsal and anal fins, and a seventh bar on caudal-fin base. Dorsal fin with dark anterior blotch covering fin membranes between dorsal-fin spines 1–3. Rest of dorsal fin, anal and pelvic fins, and base of caudal fin with dusky interradial membranes. Spinous dorsal fin, and leading edges of pelvic and anal fins with white rim. Pectoral fin translucent.

Coloration in life. Pattern of colour markings in living individuals similar to those of preserved specimens ( Fig. 2 ). Distal rim of spinous dorsal fin, spinous anal fin and leading margin of pelvic fin white. Dark markings on displaying males highly contrasted against light beige background colour. First two bars ash grey to black, subsequent six bars bright orange red. Membranes of dorsal fin between spines one and two and two and three jet black, subsequent membranes bright orange-red. Anal-fin membranes and caudal-fin membranes also bright orange red. Pelvic-fin membranes ash grey to blackish with leading edge of pelvic-fin spine and first ray iridescent whitish blue. Iridescent scales on cheek and opercular region and on side of body. Females with less contrasted bars, but also several iridescent scales on opercle and sides of body.

Distribution. Dario tigris is currently known from the type locality ( Fig. 5 ), an unnamed stream south of Mogaung and two localities between Mogaung and Myitzon (NRM 44001, NRM 44002). It has been reported to co-occur in at least one locality with Dario hysginon ( Kullander & Britz 2002) .

Etymology. The specific name tigris was inspired by the vertical stripes of this species. It is a noun in apposition representing the Greek word τίγρις, and the Latin word tigris ( Plinius 1538, Book 8, Chapter 18), both referring to the tiger, Panthera tigris (Linnaeus, 1758) sensu lato.

Remarks. Dario tigris was illustrated and discussed by Kullander & Britz (2002: pp. 363–364, Fig. 36c) who considered the two barred specimens available to them as a ‘color phase’ of Dario hysginon and ‘less likely that’ it ‘would represent another undescribed species.’

Figures

FIGURE 1. Dario tigris, (A) BMNH 2019.10.16.100, holotype, male, 16.7 mm SL:(B) BMNH 2019.10.16.101-130, paratype, female, 15.1 mm SL; Myanmar, Kachin State, unnamed mountain stream south of Mogaung.

FIGURE 2. Dario tigris, not preserved, (A) displaying male in courtship colouration and (B) female in neutral colouration. Images provided by Heng Wah Choy (A) and Frank Schäfer (B).

FIGURE 5. Comparison of melanophore pattern in bars of Dario tigris, BMNH 2019.10.16.100, holotype, male, 16.7 mm SL, and D. melanogrammus, BMNH 2019.10.16.2, male, 20.4 mm SL. Note light, almost melanophore-free area at base of scales in D. melanogrammus resulting in zigzag pattern.