Channa aurantipectoralis, Lalhlimpuia, Denis Van & Lalronunga, Samuel, 2016

Lalhlimpuia, Denis Van & Lalronunga, Samuel, 2016, Channa aurantipectoralis, a new species of snakehead from Mizoram, north-eastern India (Teleostei: Channidae), Zootaxa 4147 (3), pp. 343-350 : 344-348

Channa aurantipectoralis , new species

( Fig. 1 )

Holotype. ZSI FF 5634, 165 mm SL; India: Mizoram: Mamit District: Keisalam River, a tributary of Karnaphuli River , in the vicinity of Phuldungsei , 23°31'25"N 92°22'45"E; Lalhlimpuia , 11 February 2016.

Paratypes. ZSI FF 5635, 3, 103– 151 mm SL; PUCMF 16004, 7, 89.3–160 mm SL; PUCMF 16005, 2 , 79.3– 147 mm SL (cleared and stained); same data as holotype . PUCMF 16006, 5 , 77.0– 125 mm SL; India: Mizoram: Mamit District: Seling River, a tributary of Karnaphuli River , in the vicinity of Damparengpui , 23°40'52"N 92°22'35"E; Lalronunga , 11 December 2014.

Diagnosis. The species resembles members of the Channa gachua species group (sensu Britz 2008) in overall morphology and colour pattern, but differs from all of them in having uniformly-coloured bright-orange pectoral fins, lacking any spots, stripes or bands, and a dark V-shaped blotch on the dorsal surface of head in life. It further differs from other species of the genus by the combination of the following characters: absence of scales on the gular region, presence of a large scale on each side of the ventral surface of the lower jaw, 51–64 lateral-line scales, 34–37 dorsal-fin rays, 23–25 anal-fin rays, 13–14 pectoral-fin rays, 5½–6½ /1/ 7½–8½ transverse scale rows.

Description. Body elongate, cylindrical anterior to dorsal-fin origin, increasingly compressed posteriorly. Dorsal profile rising evenly from tip of snout to dorsal-fin origin, then sloping gently posteriorly to end of caudal peduncle. Ventral profile almost straight. Head large, profile slightly convex laterally in dorsal view, length 3.0–3.4 times in SL. Head widest halfway between posterior margin of eye and that of opercle. Eyes small, closer to snout tip than to distal opercular margin. Caudal peduncle length 1.2 times its depth.

Mouth terminal, large, with lower jaw protruding; posterior end of maxilla and premaxilla extending beyond posterior margin of eye; lips thick. Both jaws with rows of sharp, pointed teeth. Lower jaw with two rows of teeth. Vomer with canine-like teeth with eight to ten bigger teeth. Palatine teeth small, numerous. Fifth ceratobranchial slender, with numerous teeth.

Dorsal-fin rays 34 (2), 35 (2), 36 (12) or 37 (2). Anal-fin rays 23 (2), 24 (11) or 25 (5). Pectoral-fin rays 13 (12) or 14 (6). Pelvic-fin rays 5 (18). Principal caudal-fin rays 12 (1), 13 (15) or 14 (2). Total vertebrae 45 (1) or 47 (1).

Cheek scales in 5 (17) or 6 (1) rows. Pre-dorsal scales 15 (6), 16 (10) or 17 (2). Lateral line with 51 (2), 52 (2), 53 (3), 54 (2), 56 (1), 57 (2), 59 (2), 62 (2) or 64 (2) scales, extending from shoulder girdle in a horizontal line, dropping one scale row at scale 14 (1), 15 (4), 16 (6), 17 (4) or 18 (3), then continuing horizontally to caudal peduncle; several supernumerary scales on the body intercalated between regular scale rows in some paratypes (see below). Transverse scale rows 5½ /1/7½ (12), 5½ /1/8½ (5) or 6½ /1/8½ (1). One or two large scales on ventral surface of lower jaw. Cephalic sensory pores single, without multiple branches. Isthmus U-shaped.

Coloration. In preservative ( Fig. 1 ): dorsum, sides of head and body dark grey, becoming lighter posteriorly. Ventral surface of head creamish. Ventral surface of body uniformly light grey. Pectoral fin uniformly greyish, lacking spots or stripes, its interradial membrane cream, distal margin white. Dorsal, pelvic, anal and caudal fins dark grey with narrow white rim.

In life ( Fig. 2 ): dorsal and lateral surfaces of body golden yellowish, ventral surface of body light grey. An elongated dark blotch extending posteriorly from posterior margin of orbit, meeting its antimer at posterior end of occiput to form large V-shaped mark on dorsal surface of head. Ventrolateral and ventral aspect of head bluish. Upper half of body with series of 7–9 obliquely-arranged, saddle-like dark blotches or bands; a horizontallyelongate black blotch above base of pectoral fin. Pectoral fin bright orange, lacking spots or stripes. Dorsal fin bluish, submarginally orange, with whitish distal margin. Anal fin bluish, submarginally dark grey with whitish distal margin. Caudal fin golden yellow with bluish interradial membranes, orange submarginally, with whitish distal margin.

Distribution. Presently known only from Seling and Keisalam Rivers (small tributaries of Karnaphuli River) of Dampa Tiger Reserve, Mizoram, India ( Fig. 3 ). The Karnaphuli River, originating from the hills of Mizoram- Tripura border, flows southwest along the Mizoram-Bangladesh border and then through the Chittagong Hill tract of Bangladesh and finally empties into the Bay of Bengal.

Etymology. The species name, aurantipectoralis , is a Latin adjective referring to the conspicuous, orangecoloured pectoral fins of this fish.

Discussion Musikasinthorn & Taki (2001) broadly divided the family Channidae into two major groups based on the presence or absence of scales on the gular region. Species belonging to the first group are characterized by possessing scales on the gular region, viz. Channa bankanensis (Bleeker) , C. lucius (Cuvier) , C. micropeltes (Cuvier) and C. pleurophthalma (Bleeker) along with the three species of the African genus Parachanna . Species of the second group lack scales on the gular region and comprise the rest of the genus Channa . Li et al.’s (2006) molecular phylogenetic study of channids supported this division based on the single morphological character. Channa aurantipectoralis differs from C. bankanensis , C. lucius , C. micropeltes and C. pleurophthalma and all the species of Parachanna in lacking (vs. having) scales on the gular region.

Britz (2008) observed that species in clade 6 and 7 in Li et al.’s (2006) phylogenetic tree share a colour pattern characterized by a varying number of dark and light semi-circular bands on the pectoral fin. He proposed this unique pattern as the defining character for his ‘ Channa gachua species group’. The group has been acknowledged by subsequent workers (see Britz 2013; Knight 2016) and currently comprises: C. andrao Britz , C. aurantimaculata , C. barca , C. bleheri , C. gachua , C. melanostigma , C. orientalis Bloch & Schneider , C. ornatipinnis Britz , C. pardalis , C. pulchra Britz and C. stewartii . Based on the presence of 2–5 semi-concentric dark rings (see Ng et al. 1999) on the pectoral fins, Channa harcourtbutleri (Annandale) also needs to be included in this group. The recently described Channa longistomata ( Nguyen et al. 2012) is currently considered a synonym of C. gachua (see Kottelat 2013), but if valid would also be a member of the C. gachua species group of Britz (2008). Channa aurantipectoralis is very similar to members of the C. gachua species group in overall morphology, colour pattern, and specifically, in having large scales on each side of the ventral surface of the lower jaw. However, it differs from all of them in having uniformly orange pectoral fins that lack any kind of dark markings such as stripes or bands. They also differ from all members of this species group, with the exception of C. aurantimaculata and C. barca , in having more lateral-line scales (51–64 vs. 42–50). The new species further differs from Channa aurantimaculata and C. barca in having fewer scale rows below the lateral line (7½–8½ vs. 11–15), fewer dorsal-fin rays (34–37 vs. 45–52) and fewer anal-fin rays (23–25 vs. 28–36).

The presence of large scales on the ventral surface of the lower jaw is an important diagnostic character (see Musikasinthorn 2000; Li et al. 2006; Vishwanath & Geetakumari 2009). Channa aurantipectoralis differs from all other valid species of Channa , with the exception of C. amphibeus (McClelland) , C. asiatica (Linnaeus) , C. nox Zhang, Musikasinthorn & Watanabe , C. punctata (Bloch) and C. panaw Musikasinthorn along with members of ‘ C.gachua species group’, in possessing (vs. lacking) large scales on the ventral surface of the lower jaw. Channa aurantipectoralis is markedly different from C. asiatica and C. nox in possessing (vs. lacking) pelvic fins, fewer dorsal-fin rays (34–37 vs. 46–49) and fewer anal-fin rays (23–25 vs. 28–33). It also differs from C. amphibeus in having a lower number of cheek-scale rows (5 vs. 9), fewer dorsal-fin rays (34–37 vs. 50) and fewer lateral-line scales (51–64 vs. 81); from C. panaw in having more lateral-line scales (51–64 vs. 39–41), fewer pectoral-fin rays (13–14 vs. 17–20) and more circumpeduncular scale rows (28 vs. 21–24); and from C. punctata in having more lateral-line scales (51–64 vs. 38–40), more dorsal-fin rays (34–38 vs. 28–31), more scale rows above the lateral line (5½–6½ vs. 3½ –4½) and a convex head profile in lateral view (vs. concave).

The presence of a dark V-shaped blotch on the dorsal surface of head in live specimens of Channa aurantipectoralis is another unique character observed. This character is not retained in preserved specimens, and also disappears in life when the fish is under stress. A dark V-shaped blotch has also been observed in live specimens of Channa maculata (Lacepède) (pers. observation); however, the orientation is different (pointing posteriorly in C. aurantipectoralis vs. pointing anteriorly in C. maculata ) and much smaller than that observed in C. aurantipectoralis .

It is worth mentioning that the range of lateral-line scales varying from 51–64 for a single snakehead species seems rather large and is highly unusual. Out of the 18 specimens in the type series, 12 possess 51–57 lateral-line scales whereas 6 specimens have between 59 and 64 lateral-line scales. The reason for this large range is the highly irregular arrangement of scale rows in these latter specimens, in which several scales or scale rows are intercalated into the regular rows resulting in a much higher count than in the individuals without intercalated scales and regular scale rows. Given the irregularity of intercalated scales and the close correlation in snakeheads between the number of scale rows and number of vertebrae, we interpret the higher scale counts in the 6 individuals as untypical for the species. We are uncertain what may have caused these irregularities, but scale loss and subsequent irregular regeneration may be one reason. We conclude that the range of 51–57 lateral-line scales is typical for C. aurantipectoralis .

Mizoram, situated in the northeastern part of India, is endowed with three distinct river drainage systems that, although rich in fish species diversity, are poorly explored. The discovery of this uniquely-coloured species of Channa from one of the most important biodiversity hotspots in Asia highlights the lack of knowledge of the fish fauna of this underexplored part of India. It is evident from recent studies ( Britz 2008; 2013; Knight 2016; Vishwanath & Geetakumari 2009) that the north-eastern part of India and the adjacent north-westen part of Myanmar, with its distinct river drainage systems, is rich in the diversity of the genus Channa . Rüber et al. (2004) speculated that the actual major freshwater river systems in Northeast India and Myanmar have probably only existed since the Miocene and that the Miocene uplift of the Indoburman ranges played an important role in shaping the distribution pattern of badids. Similarly, we believed that the same factor played an important role in the distribution and diversification of the genus Channa in this region. However, future studies will need to demonstrate where this interesting new species belongs phylogenetically and what its biogeographic links are.

Figures

FIGURE 1. Channa aurantipectoralis; a) holotype, ZSI FF 5635, 165 mm SL; lateral, dorsal and ventral views; b) paratype, PUCMF 16005, 89.3 mm SL; lateral view.

FIGURE 2. Channa aurantipectoralis, (specimen not preserved), 154 mm SL (approx.); showing coloration in life; lateral and dorsal views.

FIGURE 3. Map showing collection locality of Channa aurantipectoralis.