Channa amphibeus ( McClelland, 1845 )

Channa amphibeus ( McClelland, 1845) View in CoL

( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 , 3 View FIGURE 3 & 7 View FIGURE 7 )

Material examined. Channa amphibeus , KUFOS-AN-2024.12, 205.0 mm SL, collected from a local fisher at the Chel River , near Gorubathan, Kalimpong District, West Bengal, India, J. Praveenraj & team, 26.09.2024; BNHS FWF 1185-86 , 180 View Materials & 420 mm SL, 2 ex, collection location same as above, 26.11.2024.

Photographs examined: Channa amphibeus , ca. 270, 370, and 500 mm SL, location details same as above.

Description. See Figs. 2 View FIGURE 2 , 3 View FIGURE 3 , 7A & B View FIGURE 7 for general appearance and Table 1 View TABLE 1 for morphometric data. A large snakehead species reaching at least 500 mm SL (present study), but reported by local fishers to reach 800 mm TL. Body elongate, round in cross section anteriorly, laterally compressed at caudal peduncle, body depth 5.9 times SL. Dorsal profile convex, rising evenly from tip of snout to dorsal-fin origin, then almost straight to base of caudal fin. Ventral contour descending gently until below opercle, almost straight to base of caudal fin. Head large, length 3.5 times SL. Head widest, halfway between posterior margin of eye and opercle. Eyes located on anterior half of head, closer to snout. Interorbital region somewhat bulging. Mouth large, posterior end of maxilla and premaxilla extending beyond posterior margin of eye. Lower jaw slightly protruding beyond upper jaw, lips fleshy. Pectoral-fin insertion almost at vertical through origin of dorsal fin. Body depth and width greatest at dorsal-fin origin. Dorsal- and anal-fin bases long, 69.9% and 46.7% SL, respectively. Premaxilla with multiple rows of small, sharp, pointed teeth. Dentary with two rows of teeth, inner row with medium- to large canines; outer row with mediumsized, villiform teeth terminating in three rows at jaw symphysis. Vomer with an inner series of large conical teeth and outer series of much smaller teeth. Palatine with external series of smaller teeth and internal row of up to nine much larger canines. Dorsal-fin rays 48–52, anal-fin rays 33–36. Caudal fin with 6–7+6–7 principal rays, and 3 dorsal and 4 ventral procurrent rays. Pectoral-fin rays 15, pelvic-fin rays 6. Lateral line with 75–93 pored scales extending from shoulder girdle in horizontal line up to caudal peduncle, continuous, not dropping a scale row after pre-drop, plus 3–4 non-pored scales on caudal-fin base; transverse scale rows in dorsoventral direction 7.5/1/13.5– 14.5, circumpeduncular scales 30–34, cheek scales 8, prepelvic scales 17–28, predorsal scales 16–19. Vertebrae 53 (n =1) with 17 abdominal and 36 caudal vertebrae. Adult male ( Figs. 2D View FIGURE 2 & 7B View FIGURE 7 ): Head wedge-shaped in dorsal view. Cheeks bulging laterally. Predorsal profile ascending very steeply in straight line from tip of snout to nape, gently convex more posteriorly up to dorsal-fin origin, and thereafter almost straight to base of caudal fin. Ventral contour convex from tip of snout to almost vertical through nape, then gently curved till pelvic-fin origin, thereafter almost straight to base of caudal fin.

Colouration in life. Specimens of 200–300 mm SL ( Figs. 2A, B, C View FIGURE 2 & 7A View FIGURE 7 ): base colour of body iridescent-green with numerous black spots, and sides with 11–12 irregular, orange or chrome- to ochre-yellow bars originating from dorsal-fin base and extending beyond lateral-line, but not reaching base of anal fin. The bars equal in width to iridescent-green interbars between them. In some specimens, at mid to posterior portion of body, bars not matching up, incomplete or bifurcating ( Figs. 2B View FIGURE 2 , & C). Dorsal surface of head greenish with numerous maroon to chrome-yellow, elongated spots forming reticulated pattern; side of head also with numerous elongated, chrome-yellow spots. Lips, snout, and postorbital region, neon-blue with rich-brown to maroon, elongated blotches. Gular region bluish. Series of 1–3, large, irregular, black spots above and posterior to opercular opening at lateral-line origin. Dorsal fin with basal half yellowish to orange, green and black subdistal bands, and narrow, white distal margin; dorsal-fin membrane with numerous black spots, arranged as five horizontal rows along entire fin length. Anal fin iridescent-green, becoming darker towards dorsal margin. Caudal fin with ochre-yellow fin rays, greenish interradial membranes, and narrow white to orange distal margin. Pectoral fin bright-orange with bluish base, and 3–4 narrow, semi-circular light brown bands; in some specimens a series of orange spots arranged in loose semi-circular lines on fin rays. Pelvic fin with pale-grey rays and greenish interradial membrane becoming darker towards tips.

Specimens of 400–500 mm SL ( Figs. 2D View FIGURE 2 , 3B View FIGURE 3 , 7B View FIGURE 7 ): Body bluish-green with numerous black spots, sides with 16– 18, narrow, maroon bars. In some specimens bars completely absent, or barely visible as highly reduced, irregular, broken blotches ( Fig. 2D View FIGURE 2 ). Head bluish-green with numerous, rounded to elongated maroon spots, more prominent on lips. Snout, lips, and portion below eye neon-blue. Dorsal and caudal fin olive-green with numerous black spots along entire fin length, subdistal margin black, and distal margin narrow yellow and white. Anal fin bluish-green with olive-green to brown fin rays, becoming darker towards margins, and narrow white distal margin; numerous black spots along entire fin length. Pectoral fin brown with orange spots arranged transversely. Pelvic fin bluish-green with greyish tips.

Colour details according to Shaw & Shebbeare (1938: 12 l): “A gorgeously coloured fish. The ground-colour is blue when viewed obliquely and iridescent green when viewed at right angles to the surface. On the body this colour is sprinkled with dark spots, uniform in size but irregular in shape. These spots are absent from the belly, sparse below the lateral line and increasingly plentiful towards the back where they coalesce. On the head, the spots are larger and rounded, rich brown below the level of the eye and becoming darker and more plentiful towards the top of the head where they coalesce. The brightest blue (green) and richest brown are in the region of the upper lip. Along the body 13–16 more or less irregular vertical bands about equal in width to the interspaces between them and extending from the dorsal to below the lateral line. These are bright orange bordered with brown and merging into brown on the back and are free from black spots. The dorsal has the basal half brown or orange, the outer half blue (green), darkening outwards but having a narrow pale blue or white edge. Pectoral deep orange. Pelvics blue. Anal iridescent blue (green) with a narrower dark border. Caudal brown at the base, then iridescent blue (green) with dark rays, then blackish with a narrow white or bluish-white border” (see Fig. 1B View FIGURE 1 ).

Colouration in preservative. See Fig. 3A View FIGURE 3 . In 10% formalin: Dorsum, sides of head and body dark-grey with black spots. Ventral surface of body pale-grey to creamy-white. Bars on sides beige. Spots on head pale-grey. Pectoral fin greyish, with 3 narrow, semi-circular grey bands. Dorsal fin dark-grey with narrow white distal margin. Anal fin pale grey with 2–3 horizontal rows of black spots. Caudal fin pale-grey with black fin rays and whitish narrow margin. Pelvic fin pale-grey with dark-grey tips. Lower jaw ventral surface and belly creamy-white, branchiostegal membrane dark grey to black.

Distribution, habitat, and ecological notes. Currently, Channa amphibeus is known only from the Chel River system ( Fig. 4 View FIGURE 4 ). The locality details mentioned in Pearson (1839) and McClelland (1845) literature reveal that this species was collected on the borders of the Chel River, not immediately from the main river, but from the dry region which possess ‘grass jungle’. The ‘dry region’ with ‘grass jungle’ actually indicates the Terai grasslands, and the specimens might have been collected during the summer or late winter. We presume that the locality from where we obtained our specimens, and the original type locality may be in close proximity as the fish described in this paper were collected from a muddy, slow-flowing, shallow stream with riparian vegetation amidst Terai grasses. From interviews with local fishers, we infer that this species grows to a length of ~ 60–80 cm TL; adults live as pairs during the dry season in submerged holes originally created (and later abandoned) by crabs.

Genetic analysis. In the maximum likelihood phylogenetic tree based on mitochondrial co1 gene sequences, C. amphibeus was recovered as the sister species of C. barca with a divergence of 3.1–3.2%. Additionally, Channa amphibeus differs from all species in the Gachua group (sensu Britz 2008), by a raw genetic distance ranging from 3.1–19.0% ( Fig. 5 View FIGURE 5 ).