Badis rhabdotus, Kullander & Norén & Rahman & Mollah, 2019

Kullander, Sven, Norén, Michael, Rahman, Md. Mizanur & Mollah, Abdur Rob, 2019, Chameleonfishes in Bangladesh: hipshot taxonomy, sibling species, elusive species, and limits of species delimitation (Teleostei: Badidae), Zootaxa 4586 (2), pp. 301-337 : 322-325

Badis rhabdotus , new species

( Fig. 11 )

Holotype. DU 9035 , male, 46.9 mm SL; Bangladesh, Sylhet Division: Sylhet District: Meghna River drainage, Pyain River at Jaflong , 25°11′4″N 92°0′59″E. M.M Rahman et al., 24 March, 2016.

Paratypes. DU 9036 , 1 , 34.6 mm SL ; DU 9037 [ex NRM 69035 (11525], 1, 27.5 mm SL; NRM 68599, 4 , 37.2 .– 39.6 mm SL; NRM 69034, 1 , 39.7 mm SL; collected with the holotype. NRM 51432, 1 , 51.2 mm SL; NRM 70335, 2 , 37.5 – 38.4 mm SL; India: Meghalaya: Wanapha River at Ummulong; H. Bleher, Sep 2009.

Diagnosis. Similar to B. badis , B. chittagongis , B. ferrarisi , B. kanabos , B. khwae , B. pallidus , B. ruber , B. siamensis , B. soraya , tuivaiei , and different from all other species of Badis in the presence of a dark blotch on the exposed cleithrum. Distinguished from B. khwae , B. ruber , and B. siamensis , in the absence of dark blotch dorsolaterally on the caudal peduncle. Distinguished from B. ferrarisi by the absence of short black bars along the middle of the side, and absence of a dark blotch on the gill cover. Distinguished from B. tuivaiei in the absence of a black blotch anteriorly on the dorsal fin, curved vs. straight vertical bars, and lower meristic values (28–29 vertebrae vs. 30–31; lateral scale row 27–29 vs. 26–32, modally 30; dorsal-fin rays XVI.8½ or XVII.7½–8½ vs. XVI.9-10, XVII.8, XVIII.8 and modally XVIII.9); from B. kanabos by the absence of black spot anteriorly on the dorsal fin, and from B. Badis by narrower interorbital space (4.8–5.5% SL vs. 6.5–8.3%, and more slender body (25.7–32.0% SL vs. 30.7–38.9%; not corrected for allometry). Similar only to Badis soraya in the presence of intense black narrow vertical bars on the sides in males, vs. indistinct or absent vertical bars on the sides, or vertical bars present but wide, not contrasting; vertical bars narrow, unpaired in both sexes, distinguishing from juvenile bar pattern in Badis , which consists of pairs of narrow bars. Distinguished from B. chittagongis and B. pallidus , particularly by the colour pattern of prominent narrow vertical stripes, vs. wide vertical bars or uniform sides. Distinguished from B. soraya by meristic values (vertebrae 28–29 vs. 27; lateral scales 28–29, exceptionally 27 vs. 25–27; dorsal-fin rays XVII.9–10, exceptionally XVI.9, vs. XIV.9–XVI.11,modally XV.10), and proportional measurements (narrower interorbital width, 4.8–5.5% SL vs. 6.3–8.8% SL; averaging lesser body depth, 25.7– 32.0%SL vs. 29.6–35.5%; not corrected for allometry).

Description. Based on Bangladeshi specimens. Proportional measurements are given in Table 5 ; selected meristics in Tables 6–7). Moderately elongate, strongly compressed laterally. Predorsal contour straight or slightly curved, sloping at same angle as slightly curved prepelvic contour, or steeper. Orbit situated in anterior half of head and level of midaxis of body. Jaws about equal anteriorly, lower jaw only slightly projecting before upper; maxilla reaching slightly posterior of vertical through anterior margin of orbit. Lower jaw articulation below middle of orbit. Well-developed tooth-patches on parasphenoid, basibranchial 3, basihyal, palatine and vomer. Dentary pores 3; anguloarticular pores 2; preopercular pores 7; nasal pores 2; supraorbital pores 3; extrascapular pores 2; supracleithral pores 2; posttemporal pores 2; coronalis pore; lachrymal pores 3; a row of free neuromasts across gap between lachrymal and anteriormost infraorbital; infraorbital pores 4.

Scales in lateral row 27 (1), 28 (5). Lateral-line scales 19/4, 21/5, 22/6, 23/6, 24/5, 25/5 (one of each). Predorsal scales 11 (2), 12 (3), 14 (1). Circumpeduncular scale rows 18 (6). Scales between first dorsal fin-spine and upper lateral line 3, posteriorly 1½ scales between dorsal-fin base and upper lateral line; full-size scales between first anal-fin spine and upper lateral line 6 (1), (7 (5). Scale rows on cheek 4, on opercle 5, on subopercle 1 (8 scales), on preopercle 1 (4 scales), on interopercle 1 (6 scales). From about fifth dorsal-fin spine, dense layer of small rounded scales, 3 on each interradial space, covering spinous dorsal-fin base up to at most middle of fin height; on base of soft dorsal fin, scales smaller, up to 7 scales in an interradial space. Anal fin from behind third spine to anterior soft rays with narrow layer of small, rounded scales, one to five in each interradial space. Caudalfin base densely scaled, up to about 10 scales on middle rays.

Dorsal-fin rays XVI.8.5 (1), XVII.7½ (1), XVII.8½ (6), XVII.9½ (1). Soft anal-fin rays 6½ (3), 7½ (5). Soft dorsal and anal fins with rounded or subacuminate tip, reaching to or slightly beyond base of caudal fin; dorsal fin slightly longer in largest male, not quite reaching to middle of caudal fin. Caudal fin rounded; principal caudal-fin rays 14 (6). Pectoral-fin rays (11 (1), 12 (2), 13 (5). Pectoral fin rounded, not reaching posteriorly to tip of pelvic fin. Pelvic fin with point formed by second soft ray, reaching more than halfway to vent.

Ceratobranchial gill-rakers 6 (6). Supraneurals 3 (6), vertebrae 15+13=28 (2), 15+14=29 (4).

Colouration in preservative. Ground colour pale beige or brown. Three scales in oblique row posterodorsally from orbit at about 1400h position black in preserved specimens, iridescent dark green in living specimens. Suborbital and preorbital stripes dark grey or brown. Tip of maxilla pale grey or white. Top of head and occipital region medially dark brown. Spot covering exposed part of cleithrum black in preserved specimens, iridescent dark green in living specimens. Cheek pale brown, gill cover dorsoposteriorly darker brown than cheek. Seven or eight distinct narrow, deep black vertical bars from about level of tip of pectoral fin to middle of caudal peduncle, each bar 1–2 scales in width, formed by dark scale margins. Posterior bars distinctly curved, concave caudad. Posteriormost bar encircling caudal peduncle; three bars anterior to that extending between dorsal vertical fin bases, remaining bars reaching to dorsal-fin base but ventrally only to level of pectoral fin base. Anteriorly on side, scattered scales with dark margins not forming bars, or only partial bars. Bars more intensely pigmented and distinctly undulating in males. Dorsal fin basally black, rest of spinous dorsal fin brown, soft fin brownish grey; each dorsal-fin lappet with white margin and narrow black submarginal streak. Anal and caudal fins pale grey. Pectoral fin hyaline. Pelvic fin grey with white leading edge. Black square or slightly elongate blotch at base of caudal fin. Dorsally and ventrally on side of caudal fin base a dark brown blotch varying in shape from round to elongate. Genital papilla black in females; black proximally in males. Ethanol-fixed specimens retain traces of red or maroon pigmentation on sides, between bars ( Fig. 11C ).

Specimens from Meghalaya. Four specimens from Ummolong in Meghalaya agree with B. rhabdotus from Bangladesh in meristics, colour pattern and mitochondrial DNA sequences, but are in a poor state of preservation, and data could not be obtained for all characters. They have 28 (2) or 29 (1) lateral row scales. Two radiographed specimens have 14+13 (1) or 15+14 (1) vertebrae.

Etymology. Named rhabdotus , from the Greek ῥαβδωτóς, meaning striped, with reference to the prominent vertical bars characterizing this species. An adjective with alternative endings, -a, -um.

Geographical distribution and habitat. In Bangladesh, specimens were sampled from a shallow sandy beach in a heavily converted area on the right bank of the Pyain River at Jaflong ( Figs 3 , 12 ). The site had some aquatic vegetation, but was otherwise bare. Seining in the main river, with a rocky bottom and current, did not yield any specimens of Badis . The sampling was made at the extreme low water season and may not have been characteristic of the biotope of the species. Georeferenced GenBank sequences ( Fig. 1 ) show that B. rhabdotus has a wide distribution in the Meghna River basin, including the lower Barak River, tributaries in southern Meghalaya, distant Karnafuli headwaters, and possibly the Madopkundo Falls in Bangladesh.

Figures

FIGURE 1a. clustering of OTUs of Badis kyar, B. ferrarisi, B. corycaeus, B. assamensis, and GenBank samples identified as B. assamensis. Excerpt from bPTP delimitation tree of species of the Badidae, based on coi sequences (Fig. S3). New sequences are labeled with tissue collection identifiers in NRM. Sequences from GenBank are labeled with Accession number and original determination.

FIGURE 3. Collecting sites of species of Badis and Dario in Bangladesh.

FIGURE 11. Badis rhabdotus. A, holotype, DU 9035, adult male, 46.9 mm SL; B paratype, NRM 68599, adult female, 37.2 mm SL; C, paratype, NRM 69034, adult female, 39.7 mm SL, preserved in 95% ethanol. All from Bangladesh, Pyain River at Jaflong.

FIGURE 12. General view of collecting site of Badis rhabdotus at Jaflong. Specimens were seined in shallow water over sand bottom.