Dario neela, Britz & Anoop & Dahanukar, 2018

Britz, Ralf, Anoop, V. K. & Dahanukar, Neelesh, 2018, Dario neela, a new species of badid fish from the Western Ghats of India (Teleostei: Percomorpha: Badidae), Zootaxa 4429 (1), pp. 141-148 : 142-146

Dario neela , new species

Figures 1–2

Holotype. BNHS FWF 612 , 31.2 mm SL; India: Kerala: from a small unnamed stream between Periya and Boys Town, a tributary of the Kabini river , 11°49’27"N 75°51’45"E, 738 m asl; V.K. Anoop and Liju Thomas, 20 June 2016.

Paratypes. BNHS FWF 613–623, 11, 16.6–28.5 mm SL, same data as holotype . BNHS 624–625, 2, 21.5–21.7 mm SL, same data as holotype, but preserved in ethanol . BNHS FWF 626–627, 2, 16.7– 7.8 mm SL, c&s, same data as holotype .

Diagnosis. Dario neela differs from all other species of the genus Dario by the male colour pattern, which shows wide rims of iridescent blue in all median fins and the pelvic fin. It is further distinguished from all Dario spp. except D. urops by the number of abdominal vertebrae (14 vs. 11–13), and from all species of Dario except D. urops and D. huli by the presence of a conspicuous black blotch on the caudal-fin base. It is distinguished from D. urops by lacking the horizontal suborbital stripe (vs. having the suborbital stripe), and possessing a series of up to 8 black bars on the body (vs. 2–3 black bars restricted to the caudal peduncle). It differs from D. huli by having more vertebrae (14+13–14=27–28 vs 13+13=26), 27 scales in a lateral row (vs. 25), absence of tubed lateral-line scales (vs. 3–5 tubed lateral-line scales) and by absence of teeth on hypobranchial 3 (vs. presence of teeth).

Description. For general appearance see Figs. 1–2 ; morphometric data are provided in Table 1.

Body elongate, moderately laterally compressed in males, nearly round in cross section in females. Predorsal contour convex, giving head a rounded appearance. Eye situated in anterior half of head. Snout short. Mouth terminal. Rictus situated at vertical through anterior third of eye. Dorsal contour of body almost straight; prepelvic contour slightly convex, continuing almost straight up to pelvic-fin origin, slightly concave in males between pelvic fin and anal fin, but straight to slightly convex in females; dorsal and ventral contours converging towards caudal peduncle. Caudal peduncle with parallel sides, tapering slightly posteriorly.

Lateral-line canal pores on head: dentary pores 3 (d2–d4), anguloarticular pores 2 (aa1–aa2), preopercular pores 5 (p1, p3–p5, p7), nasal pores 2 (n1–n2), supraorbital pores 3 (f1–f4), extrascapular pores 3 (ex1–ex3), posttemporal pores 2 (po1–po2), coronalis pore 1 (cor), lachrymal pores 2 (l1, l3); no infraorbital pores.

Scales ctenoid on sides, cycloid on top of head. Predorsal scales 4–5 anterior to coronalis pore, 9–10 posteriorly. Three to four rows of scales on cheek. Circumpeduncular scales 16. Tubed lateral-line scales entirely absent; instead lateral line represented by superficial neuromasts located in shallow central depression on 16–21 scales; however, one large male with a single tubed scale in second scale row behind posterior posttemporal canal opening (po2). Scales in lateral row 27. Scales in transverse row 1–2 small scales at anal-fin base plus 8 large scales on sides plus 2 small scales at dorsal-fin base.

Dorsal-fin rays XIII+8 (1), XIII+9 (2), XIV+8 (7), XIV+9 (2) or XIV+10(2). Anal-fin rays III+7 (3) or III+8 (11). Pectoral-fin rays 12 (10) or 13 (4). Pelvic-fin rays I+5. Principal caudal-fin rays 7+7 (14), 4 dorsal and 5 ventral procurrent rays (2). Vertebrae: 14+13=27 (1) or 14+14=28 (1). Caudal-fin skeleton consisting of one epural and two hypural plates, suggesting fusion of hypurals 1+2 and 3+4+5. Three slender supraneurals in front of dorsal-fin pterygiophores. Teeth present on vomer and palatine, on circular patch on posterior parasphenoid and on upper and lower pharyngeal jaws, but absent from hypobranchial 3 and basihyal. Seven elongate and pointed gill rakers on lateral face of lower limb of first branchial arch. Jaws with multiple rows of minute conical slightly recurved teeth.

Interradial fin membranes of spinous dorsal fin projecting as short fin lappets, which in males extend beyond tips of spines. Soft dorsal and anal fins with rounded (females) or slightly pointed tips (males), extending beyond base of caudal fin in males. Pectoral fin reaching to vertical through base of seventh dorsal-fin spine. Pelvic fin not reaching anus in juveniles and females, but reaching posteriorly to anus (in male holotype and 28.5 mm SL male paratype with apparently damaged fin tips) or beyond anterior base of anal fin (25.8 mm SL male paratype with undamaged fin). Caudal fin rounded to truncate. One female paratype (21.0 mm SL) with about 20 large ripe eggs in ovaries.

Colouration in alcohol. Colour pattern sexually dimorphic. Overall colouration in males dusky greyish black with up to seven black bars in posterior third of body starting at about vertical through anal-fin base ( Fig. 1 ). Preorbital stripe faint. Horizontal suborbital stripe absent. Dorsal part of head, black, much more darkly pigmented than cheeks. Opercular bones also with denser covering of melanophores appearing darker. All fin rays and fin membranes densely covered with melanophores appearing dusky greyish to blackish, including pectoral fin. Caudal-fin base with black blotch. Caudal fin with indistinct caudal fin band separated from caudal fin blotch by lighter area in front of it. Preorbital stripe present but faint; horizontal suborbital stripe absent. Dorsal part of head with dense aggregations of melanophores between eyes appearing darker than rest.

In females, background colour light beige. Body peppered with numerous scattered melanophores. Three to four darkly pigmented scales above pectoral fin separated from each other by lightly pigmented scale appearing as short midlateral bars or blotches. Posterior third of body with up to eight narrow bars expressed as zig-zagging black lines. Caudal-fin base blotch distinct and separated from posteriormost zigzagging bar by crescentic light area forming an anterior halo around caudal-fin blotch. All fin rays and membranes with peppering of melanophores, but pectoral fin only with rows of melanophores following margins of fin rays otherwise transparent.

Coloration in life. Males upon capture with blackish blue body and intensely light blue iridescent fins, faded when photographed in photo tank to greyish blue body colour and light bluish grey but still iridescent dorsal, anal, pelvic and caudal fins ( Fig. 2A ). Females with an overall light beige colour on body and transparent fins, with no striking markings compared to preserved specimens ( Fig. 2B ).

Geographical distribution. Dario neela has been collected so far only from a small tributary of the headwaters of the Kabini River (part of the larger Cauvery river system) in northern Kerala ( Fig. 3 ). At the time of capture, the unnamed stream from which Dario neela was collected was a small, clear-water stream, up to 1.5 m wide and 0.5 m deep, with a sandy bottom ( Fig. 4 ). The fish were collected along the edges of the stream from algal mats, in between stems and roots of Colocasia (Arecaceae) and from among bamboo branches hanging into the water. Associated species comprised: Schistura semiarmata , S. denisoni , and Devario malabaricus .

Etymology. The species name neela is derived from the Malayalam word mnoe, ‘Nīla’, for blue and alludes to the striking iridescent blue colour of males. A noun in apposition.

Molecular data. In the mitochondrial CO1 gene, the uncorrected p-distance between Dario neela and its Western Ghats congeners D. urops and D. huli was 5.9% and 13.1%, respectively ( Table 2), and 19.6% between D. neela and the Gangetic congener D. dario .

Figures

FIGURE 1. Dario neela; India: Kerala; A BNHS FWF 612, holotype, male, 31.2 mm SL; B BNHS FWF 613–623, paratype, female, 21.0 mm SL; C BNHS FWF 613–623, paratype, male, 25.8 mm SL; D BNHS FWF 613–623, paratype, female, 16.6 mm SL. Note pelvic-fin rays damaged and not reaching vent in A, but extending beyond anal-fin base in C; and series of dark brown midlateral scale markings in B–D.

FIGURE 2. Dario neela; India: Kerala; A BNHS FWF 612, holotype, male, 31.2 mm SL,slightly oblique lateral view; B BNHS FWF 613–623, paratype, female, 20.6 mm SL, lateral view. Note differences in live colouration between male (A) and female (B) and eggs visible through body cavity in (B).

FIGURE 3. Map showing type localities of Dario neela, D. huli and D. urops.

FIGURE 4. Habitat of Dario neela near type locality in Wayanad, Western Ghats, India.