Devario altus, Sudasinghe & Pethiyagoda & Meegaskumbura, 2025

Sudasinghe, Hiranya, Pethiyagoda, Rohan & Meegaskumbura, Madhava, 2025, Species without borders: the diversification of giant danios in Sri Lanka (Teleostei, Danionidae, Devario), Evolutionary Systematics 9 (2), pp. 229-258 : 229-258

Devario altus sp. nov.

Fig. 13 A – C

Devario monticola Batuwita, de Silva & Udugampala, 2017 (in part).

Type materials.

Holotype. 2025.04.01.NH , 48.7 mm SL, Bopathalawa, Menik Palama Farm, Agra Oya (Mahaweli basin) , 6°48'56"N, 80°42'23"E, 1580 m asl, H. Sudasinghe, 14 June 2019 .

Paratypes. 2025.04.02.NH , 1, 44.2 mm SL (same data as holotype) ; DZ 5260 , 13, 41.9–54.9 mm SL (same data as holotype) .

Diagnosis.

Devario altus sp. nov. is distinguished from its Sri Lankan congeners by the combination of the following characters and character states: anal-fin origin posterior to dorsal-fin origin, beneath 3 rd branched dorsal-fin ray; 1 st infraorbital usually bearing a laterally-directed process; P-stripe continuous, not bifurcated anteriorly; interstripe I + 1 long, extending uninterrupted anterior to vertical through pelvic-fin origin; caudal peduncle long, 19.2–21.4 % SL, shallow, 8.8–10.5 % SL; body shallow, its depth 21.8–26.0 % SL; dorsal-fin height 19.0–23.2 % SL; dorsal-fin base length 15.1–18.2 % SL; anal-fin base length 16.4–20.5 % SL; pelvic fin height 12.9–16.6 % SL; pectoral-fin height 20.3–23.4 % SL; head depth 17.3–19.6 % SL; scales between lateral line and dorsal-fin origin 6–7 ½; circumpeduncular scales, 13–14; branched dorsal-fin rays 8 ½ - 10 ½.

Specifically, D. altus sp. nov. differs from D. malabaricus by possessing (in 73 percent of specimens) a process on the 1 st infraorbital vs lacking (in 95 percent of D. malabaricus ); having the P-stripe continuous, not bifurcated anteriorly (vs P-stripe usually bifurcated anteriorly); interstripe I + 1 long, extending uninterrupted anterior to vertical through pelvic-fin origin (vs short, not extending uninterrupted anterior to a vertical through the pelvic-fin origin in D. malabaricus ); a caudal peduncle length of 19.2–21.4 % SL (vs 12.3–19.4 % SL); a body depth of 21.8–26.0 % SL (26.1–35.4 % SL); and scale rows between lateral line and dorsal-fin origin 6–7 ½ (vs 7 ½ - 9).

The new species is distinguished from D. memorialis by having the anal-fin origin beneath the 3 rd branched dorsal-fin ray, distinctly posterior to dorsal-fin origin (vs on vertical through dorsal-fin in D. memorialis ); the anal-fin base length 16.4–20.5 % SL (vs 20.0–23.4 % SL); a head depth of 17.3–19.6 % SL (vs 14.1–15.8 % SL); and 13 or 14 (vs 15–18) circumpeduncular scales.

Devario altus sp. nov. differs from D. micronema by having the I + 1 interstripe long, extending uninterrupted anterior to a vertical through the pelvic-fin origin (vs short, not extending uninterrupted anterior to a vertical through the pelvic-fin origin in D. micronema ); having the P-stripe continuous, uninterrupted anteriorly (vs P-stripe usually interrupted anterior to pelvic-fin origin with bars or blotches); having a longer caudal peduncle, 19.2–21.4 % SL (13.2–20.0 % SL); having a body depth of 21.8–26.0 % SL (vs 23.5–36.6 % SL); and having 6–7 ½ (7 ½ - 9 ½) scale rows between lateral line and dorsal-fin origin.

It is distinguished from Devario pathirana by a shallower body (21.8–26.0 % SL, vs 32.4–36.9 % SL in D. pathirana ); a shallower caudal peduncle depth of 8.8–10.5 % SL (vs 11.3–13.1 % SL); a shorter dorsal-fin base (15.1–18.2 % SL, vs 19.0–23.8 % SL); a shorter anal-fin base (16.4–20.5 % SL, vs 20.7–22.8 % SL); a shorter pelvic fin (12.9–16.6 % SL, vs 16.1–18.8 % SL); a shorter pectoral fin (pectoral-fin height 20.3–23.4 % SL, vs 23.8–27.9 % SL); 6–7 ½ (vs 8–8 ½) scale rows between lateral line and dorsal-fin origin; and 8 ½ - 10 ½ (vs 11 ½) branched dorsal-fin rays.

Devario altus sp. nov. is genetically distinct from D. malabaricus , its closest congener, by 1.2–1.7 % in the cox 1 DNA barcoding marker and genetically distinct from the remaining species of Sri Lankan Devario by more than 3.6 %. Some populations of Devario in the central hills (‘ D. cf. malabaricus (highland phenotype) ’) possess a color pattern resembling that of D. altus sp. nov.: however, some of the individuals sequenced from these populations contain the mitochondrial haplotype for D. altus sp. nov., while most others contain the D. malabaricus mitochondrial haplotype. Sexual dimorphism is apparent in D. altus sp. nov., with males possessing (and females lacking) tubercles on the branched rays of the pectoral fin.

Description.

For general appearance, see Fig. 13 A – C ; morphometric data are provided in Suppl. material 2. Head and body laterally compressed, elongate. Body depth greatest at pelvic-fin origin. Snout length subequal to eye diameter. Medial margins of dentaries straight, parallel, with an indentation (‘ danionine notch’) anteriorly. Well-developed dermal grooves present along supraorbital shelves. Small, rounded, symphysial knob present, fitting into shallow groove on inner margin of upper jaw. Lower jaw slightly longer than upper. First infraorbital with a process (n = 11) or smooth (n = 4). Tubercles on lower jaw rounded, arranged in a mediodorsal band of 2–3 rows, tapering to a single row posteriorly and towards symphysis, present in both sexes. Single row of rounded tubercles on upper margin of upper jaw. Pectoral-fin tubercles present in males. Both maxillary and rostral barbels present. Rostral barbel longer than maxillary barbel, not reaching anterior margin of orbit; maxillary barbel short, not reaching anterior margin of orbit. Lateral line complete, declining steeply for first 7 scales, then curving parallel to ventral body outline, running low on caudal peduncle, terminating on caudal-fin base, with 36 (2), 37 (6), 38 (3), 39 (1), 40 (2), or 41 (1) pored scales on body, plus 1–2 on caudal-fin base. Median predorsal scales 15 (3), 16 (10), 17 (1), or 18 (1). Lateral scale rows between origins of dorsal and pelvic fins 6 + 1 + 1 (2), ½ 6 + 1 + 1 (6), 7 + 1 + 1 (2), or ½ 7 + 1 + 1 (5). Circumpeduncular scales 13 (7) or 14 (8). Dorsal fin with 2–3 unbranched rays, 8 ½ (1), 9 ½ (10), or 10 ½ (4) branched rays, origin anterior to vertical through anal-fin origin, distal margin straight. Anal fin with 3 unbranched rays, 12 ½ (5), 13 ½ (7), 14 ½ (2), or 15 ½ (1) branched rays, distal margin slightly concave. Pectoral-fin with 1 unbranched and 9 (5), 10 (8) or 11 (2) branched rays, adpressed fin just reaching or surpassing pelvic-fin origin; axial lobe well developed. Pelvic fin with 1 unbranched and 6 (6), or 7 (9) branched rays, origin midway between anal-fin origin and pectoral-fin origin; tip of adpressed pelvic fin not reaching anal-fin origin. Pelvic ‘ axillary’ scale present. Caudal fin with 9 + 8 (15) branched rays, forked, lobes subequal, rounded distally.

Color pattern.

For condition in life, see Fig. 13 A ; in preservative, see Fig. 13 B, C . In preservative, mid-dorsal stripe narrow, extending from occiput to caudal peduncle. Cleithral spot vertically elongate, covering part of first lateral-line scale and scale above it. P-stripe broad, two scale-widths wide anteriorly, 1 scale-width wide posteriorly, continuing to end of medial caudal-fin rays; anteriorly uninterrupted above pectoral and pelvic fins, bordered dorsally and ventrally by narrow I + 1 and I, respectively. Interstripe I narrow, of uniform width, about ¼ - ⅓ width of P-stripe, slightly narrow to P- 1, slightly narrower than I + 1. Interstripe I + 1 narrower anteriorly, about ½ - ⅓ width of P-stripe, wider posteriorly, subequal to P-stripe, uninterrupted anterior to pelvic-fin origin. P + 1 originating above middle of pectoral fin, narrower than P, subequal I + 1 anteriorly, tapering to caudal peduncle, not reaching caudal-fin base. Interstripe I + 2 absent. P + 2 absent. P- 1 narrower than P, faint, with scattered melanophores, tapering to caudal peduncle, not reaching caudal-fin base; I- 1, P- 2 absent. Anterior bars indistinct or absent. Dorsal and anal fins hyaline, with light scattering of small melanophores along interradial membranes. Caudal-fin rays pigmented anteriorly; both rays and interradial membranes pigmented posteriorly. Pectoral and pelvic fins hyaline.

Habitat and distribution.

Among the localities sampled in the central hills, the only one in which the mitochondrial genotype consists solely of D. altus is Bopathalawa, at 1580 m asl, the highest elevation at which any species of Devario has been recorded in Sri Lanka. Here, the 1–2 m-wide stream traverses Manik Palama, a dairy farm. The only other fish recorded here was the exotic Poecilia reticulata Peters, 1859 .

Etymology.

The species-name altus is Latin for ‘ high’, an allusion to this species being restricted to the Sri Lankan highlands. Applied as a noun in apposition. Suggested vernacular name in English: Sri Lanka Montane Danio .

Figures

Figure 13. Coloration of Devario altus sp. nov., A. In aquarium (~ 50 mm SL); B. In preservative, holotype, 2025.04. 01. NH, 48.7 mm SL; C. Paratype, DZ 5260 C, 52.1 mm SL. Bopathalawa, Menik Palama Farm, Agra Oya (Mahaweli basin), Sri Lanka. Holotype of D. Danio micronema Bleeker, 1863 a, RMNH. PISC. 2746 A, 60.0 mm SL, Ceylon; and syntype of E. Danio lineolatus Bleeker, 1863 a, RMNH. PISC. 2746 B, 59.2 mm SL, Ceylon.