Pethia arunachalensis, Shangningam & Kosygin & Chowdhury, 2019

Shangningam, Bungdon, Kosygin, Laishram & Chowdhury, Basudhara Roy, 2019, Pethia arunachalensis, a new species of small barb (Teleostei: Cyprinidae) from Arunachal Pradesh, India, Records of the Zoological Survey of India 119 (4) : -

Pethia arunachalensis sp. nov.

( Figure 1 )

Common name: Arunachal barb.

Material examined: Holotype: 34.0 mm SL, India, Arunachal Pradesh, Changlang District, Nao-dhing River near Miao ( Brahmaputra River drainage), 27º30 ꞌ 16 ꞌꞌ N 96º10 ꞌ 51 ꞌꞌ E, 230 m above sea level, 12-XI-2009, coll. J.K. Dey and party (Regd. No. ZSI FF 7162) . Paratypes. 7 ex.,

30.1−33.0 mm SL, same data as holotype, two paratypes ,

30.1−31.1 mm SL were dissected for osteology (ZSI FF 7163).

Diagnosis: Pethia arunachalensis sp. nov. differs from all recognized congeners of Pethia by the combination following characters: small body-size (30.1−34.0 mm SL), incomplete lateral line with 6–7 lateral line pored scales, predorsal scales 8-9, last simple dorsal-fin ray osseous and serrated posteriorly with 16-18 serrae, circumpeduncular scales 12 and a distinct black caudal spot encompassing the 17 th- 19 th lateral line scale.

Description: General body shape in Figure 1 . Morphometric data for the types provided in Table 1. Body short, moderately deep, its depth at dorsal-fin origin (40.4-44.0 % SL), compressed laterally. Predorsal contour convex, rising gradually from snout tip to dorsal-fin origin, then sloping moderately towards caudal-fin base. Caudal peduncle elongated, its depth slightly less than or equal to its length, concave in both dorsal and ventral profiles. Ventral profile convex, from tip of snout up to base of pelvic-fin origin, running slightly conventional to anal-fin origin then slanted downward from anal-fin origin near posterior end of anal-fin base, then almost straight to caudal-fin base.

Head small, laterally compressed, its length28.0-31.2%

SL. Snout rounded, smooth, longer than to eye diameter,

its length (27-31 % HL). Eyes small, its diameter 13-15 %

HL, dorso-laterally positioned, nearer to the tip of snout than to the operculum. Mouth small, subterminal, angle of gape almost reaching vertical through anterior margin of orbit. Upper lip fairly thicker and fleshy than the lower lip, lower lip intermittent medially. Barbels absent.

Dorsal-fin originating vertically opposite to the origin of pelvic-fin, its origin slightly nearer to the caudal-fin base, last ray almost crossing to about vertical of base of anal-fin. Dorsal-fin with three unbranched and 8½ branched rays, last unbranched dorsal-fin ray strong and serrated posteriorly by 16–19 serrae. Pectoral-fin with one unbranched and 10 (5) or 11 (3) branched rays, its tip somewhat pointed, attaining 1- 2 scales front to pelvic-fin origin.Pelvic fin with one unbranched and seven branched rays, its tip attaining anal opening when adpressed. Anal-fin with three unbranched and 5½ branched rays, distal border slightly straight, its tip reaching two or three scales anterior to caudal-fin base when adpressed. Caudal-fin forked, lobes subequal, upper lobe slightly longer with 10+9 principal rays, dorsal procurrent 4(6) or 5(2) and ventral procurrent 4(8) rays.

Lateral line incomplete with six (3) or seven (5) pored scales, 22 (6)–23(2) scales in lateral sequence, running slightly curve ventrally in middle of the body. Scales between dorsal-fin origin and lateral line 4½, between lateral line and pelvic-fin origin 4½. Predorsal scales 8 (5) or 9 (3), pre-anal scales 17(2)–18(6), circumpeduncular scales 12 (8). Dorsal-fin base covered with seven scales. Pelvic axillary scale present, reaching to one-third of adpressed pelvic-fin length. Total number of vertebrae 4+27–28. Gill rakers two on epibranchial, one at angle, and six on ceratobranchial.

Colour: In preservative, dorsum light brown, predorsal midline dark brown. Body background reddish brown laterally, lower parts of body behind lateral line whitish pale, snout greyish and lower part of head pale yellow. A black distinct caudal spot covering over lateral-line scales 17 th and 19 th above the posterior end of the anal-fin base. Fins hyaline without pigmentation.

Distribution: Pethia arunachalensis is currently known only from the Nao-dhing River near Miao, Changlang District, Arunachal Pradesh, India ( Figure 2 and 3 ).

Etymology: The species is christened after the state

Arunachal Pradesh, the type locality .

Discussion: Pethia arunachalensis sp.nov. is compared with existing 39 congeners in the genus. A total of eight species are considered valid in the Ganga-Brahmaputra drainage viz., P.aurea , P.canius , P. conchonius , P. gelius , P. guganio , P. phutunio , P. shalynius and P. ticto . For the genus Pethia , the arrangement and position of the lateral line forms a significant diagnostic character with variances in scale arrangement, and the complete or incomplete lateral line being used as noteworthy characters for distinguishing species ( Kottelat and Pethiyagoda, 1991; Meegaskumbura et al., 2008).

Pethia arunachalensis is unique from all known congeners except P. ticto occurring in the Ganga-Brahmaputra drainage in having more scales around caudal peduncle (12 vs. 8-10 in P. aurea , P. canius , P. conchonius , P. gelius , P. guganio , P. phutunio and P. shalynius ). Although Pethia arunachalensis is similar to P. ticto in having same scale count around the caudal peduncle, P. ticto has a distinct black humeral spot encompassing 4-5 lateral line scale which is absent in the new species. Pethia arunachalensis can be further distinguished from P. ticto by having more transverse scale rows between lateral line and pelvic-fin origin (4½ vs. 4), more prepelvic (9-10 vs. 5-7) and preanal (17-18 vs. 11-14) scales.

The new species Pethia arunachalensis is notable in having lateral line scales (22-23 vs. 20-21 in P. canius and P. phutunio ; 24–26 in P. conchonius ; 25-26 in P.aurea ; 28- 29 in P. guganio ), more principal caudal-fin rays (10+9 vs. 9+ 8 in P. aurea , P. canius and P. gelius ), absence (vs. presence of black band encircling the caudal peduncle in P. aurea , P. canius and P. gelius ). It is more notable in having fewer branched pectoral-fin rays (10-11 vs. 12-14 in P. conchonius , P. gelius , P. phutunio and P. shalynius ), transverse- scale rows between lateral line and pelvic-fin origin (4½ vs. 2 in P. canius , 2½ in P. gelius , 3-3½ in P. aurea , P. phutunio , 2½-3½ in P. shalynius ; 5½ in P. conchonius and P. guganio ) and absence (vs. presence of a streak along mid-body in P. guganio and P. shalynius ).

Currently, there are 15 valid species of Pethia recognised from the Chindwin– Irrawaddy drainage: P. atra , P. didi , P. erythromycter , P. khugae , P. macrogramma , P. manipurensis , P. meingangbii , P. nankyweensis , P. padamya , P. poiensis , P. stoliczkana , P. tiantian P. ornata , P. thelys and P. yuensis . Pethia arunachalensis can be straightforwardly notable from P. macrogramma , P. stoliczkana and P. tiantian by the presence of incomplete (vs. complete) lateral-line scales, absence (vs. presence) of humeral spot and fewer (10-11 vs. 12–14) branched pectoral fin rays. Pethia arunachalensis share similar character in having an incomplete lateral-line with the rest twelve species. However, it can be distinguished from them in having lateral-line scales (22-23 vs. 19–20 in P. didi ; 25-29 in P. atra ; 28-30 in P. khugae ), absence (vs. presence of a longitudinal stripe along the lateral-line scale in P. atra , P. khugae and P. poiensis ), absence (vs. presence of humeral mark in P. didi , P. meingangbii , P. manipurensis and P. padamya ), absence (vs. presence of maxillary barbels in P. didi , P. nankyweensis and P. padamya ), absence (vs. presence of a dark band encircling the caudal peduncle in P. erythromycter , P. nankyweensis , P. ornata , P. thelys and P. yuensis ), preanal scale (17−18 vs. 12 in P. meingangbii ; 14 in P. yuensis ; 16 in P. manipurensis ; 19 in P. atra ), more circumpeduncular scales (12 vs. 8 in P. manipurensis ; 10 in P. poiensis ), transverse scale rows between lateral line and pelvic-fin origin (4½ vs. 2½ in P. ornata ; 3½ in P. erythromycter and P. thelys ; 5 ½ in P. khugae ), shorter caudal peduncle (14.8–18.4% SL vs.

18.9–21.9 in P. erythromycter and P. didi ;19.0- 22.2 in P. khugae and P. thelys ; 21.6-23.2 in P. nankyweensis ).

Pethia arunachalensis is compared with other two known species of Pethia described from Mizoram, northeast India: P. expletiforis from Kaladan and P.rutila from Karnaphuli River drainages respectively. The new species shows differences from the two by the presence of incomplete (vs. complete) lateral line, fewer (10-11 vs. 12-13) branched pectoral-fin rays, more (4½ vs. 3½) transverse scale rows amongst lateral line and pelvic-fin origin.

Pethia arunachalensis is notable from other nine species of Pethia occurring in the southern India in possessing an incomplete lateral line (vs. complete in P. lutea , P. punctata , P. setnai and P. striata ), absence (vs. presence of humeral spot in P. longicauda , P. nigripinna , P. pookodensis , P. sahit and P. sanjoymoluri ) and transverse scale rows 4½/1/4½ (vs. 4½/1/2-2½ in P. nigripinna and P. sahit ; 3½/1/3½ in P. longicauda and P. pookodensis ; 4½/1/ 4 in P. sanjaymoluri ).

Pethia arunachalensis differs from other known five Sri Lankan congeners in the absence (vs. presence of a large vertically-elongated humeral band in P. bandula , P. cumingii and P. reval and three black bards with the addition of vertical bar beneath the dorsal-fin base in P. nigrofasciata ), an incomplete lateral line (vs. complete in P. nigrofasciata ) and more transverse scales rows 4½/1/4½ (vs. 2½/1/2½ in P. melanomaculata ; 3½/1/3½ in P. cumingii and P. reval ).

Figures

Figure 1. Pethia arunachalensis sp. nov., (Holotype, ZSI FF 7162, 34.0 mm SL).

Figure 2. Map showing type locality of Pethia arunachalensis.

Figure 3. Noa-dhing River, type locality of Pethia arunachalensis.