Channa rara, Britz & Dahanukar & Anoop & Ali, 2019

Britz, Ralf, Dahanukar, Neelesh, Anoop, V. K. & Ali, Anvar, 2019, Channa rara, a new species of snakehead fish from the Western Ghats region of Maharashtra, India (Teleostei: Labyrinthici: Channidae), Zootaxa 4683 (4), pp. 589-600 : 590-592

Channa rara , new species

( Figs. 1–3 )

Holotype. BNHS FWF 1003 , 87.6 mm SL, India: Maharashtra: Ratnagiri District: Jagbudi River near Khopi Village , on road Kumbhad—Shirgaon , Khed Taluka ; 17.68° N, 73.52° E; 47 m asl; N. Dahanukar et al., 21 March 2014.

Paratypes. BNHS FWF 1004-1005 , 2 , 82.1–90.3 mm SL, same data as holotype .

Diagnosis. Channa rara is a member of the Gachua group as evidenced by the possession of alternating concentric dark and light bands in the pectoral fin ( Fig. 1a ). Among species of the C. gachua group it can be readily distinguished by the possession of one or more ocelli in the posterior part of the dorsal fin in adults (vs. ocelli absent from posterior part of dorsal fin or with 1, rarely 2–3, ocelli in juveniles only). It is further distinguished from all species of the C. gachua group, except C. aurantimaculata Musikasinthorn , C. bleheri Vierke , C. orientalis Bloch , C. ornatipinnis Britz , C. pulchra Britz , and C. stiktos Lalramliana et al. by having 6–7 dark concentric bands on the pectoral fins (vs. only 3–5 bands or bands absent).

Description. Body elongate, round in cross section anteriorly, laterally compressed at caudal peduncle, body depth 6.2–6.7 times in SL. Head large, length 3.3–3.5 times in SL. Head widest halfway between posterior margin of eye and that of opercle. Mouth large, maxilla extending posteriorly beyond jaw angle, lips fleshy. Both jaws with multiple rows of minute sharp, pointed teeth, but no caniniform teeth present. Vomer with only a few caniniform teeth. A series of larger teeth on palatine. Pectoral-fin rays 14–15. Dorsal-fin rays 34. Anal-fin rays 22. Caudal-fin rays (including procurrent rays): 2+6+7+1(1), 2+7+7+1 (1), 1+6+6+1(1). Predorsal scales 13(1), 14(1), 15(1). Lateral line with 43 scales extending from shoulder girdle in a horizontal line, but dropping one scale row at scale 13, then continuing horizontally to end of caudal peduncle. Scales above lateral line 3.5 and below 6.5 at level of analfin origin. Postorbital scales 4+3 (2) or 4+4 (1). Circumpeduncular scales 22. Prepelvic scales 10. A single scale on ventral aspect of anguloarticular.

Colouration. In alcohol, dorsal and lateral sides of head dark grey, with lighter, beige area on cheek; ventral area of head lighter grey with some beige marbling on opercular area ( Fig. 1 ). Isthmus darker grey anteriorly, light beige posteriorly close to gill membrane posterior margin. Dark grey colour of head extending onto dorsal half of anterior body, becoming lighter posteriorly; dorsal half of body otherwise with indistinct 7–8 large darker blotches, separated by lighter areas, especially in posterior part near caudal peduncle (first below dorsal-fin rays 4–5, followed by blotches below rays 8–10, 14–16, 19–21, 25–27, 29–30, 32–33). Lateral and ventral sides of body uniformly light beige. Dorsal fin with lighter grey fin rays and darker grey fin membrane, its posterior end with a large black ocellus (between fin rays 30–33(1), 32–34(1), 29–31(1)), sometimes with one or two additional smaller, less conspicuous ocelli in front of it. Caudal fin grey with series of vertical irregular light beige lines giving the caudal fin a chequered or marbled appearance. Anal fin grey, posteriorly sometimes with oblique light beige lines. Pectoral fin with dark grey blotch at base followed by 7–8 light beige bands alternating with 6–7 concentric grey bands. Pelvic fins light grey with light beige distal margin.

In life, colour pattern much more contrasted ( Figs. 2 , 3 ). Head dark brown, on dorsal and dorsolateral sides with numerous black spots; lighter brown to beige with bronze sheen on sides; darker grey, showing some lighter whitish line marbling on ventral surface. Darker blotches along dorsum conspicuous, forming a chevron-like pattern with darker oblique lines on lateral and ventral sides of body. Dorsal fin with series of 10–12 black small spots more or less regularly spaced along fin base, usually situated at base of fin rays. Dorsal-fin membrane with less conspicuous marbling and darker spots and lines especially on fin rays. Basal two-thirds of fin membrane with hazy whitish-blue iridescence followed distally by translucent band and submarginally with a narrow light-brown band and whitish blue margin. Posterior dorsal-fin ocellus black, conspicuous; additional ocelli less conspicuous. Caudal fin brown with light-beige marbling lines, forming a caudal-fin ocellus in one of the paratypes (90.3 mm SL). Anal fin light beige, slightly translucent, with a few marbled white lines in posterior part. Pectoral fin translucent with grey basal blotch and alternating concentric brown and beige bands. Pelvic fins light beige.

Juveniles of ca. 30–34 mm SL with overall brownish colour and black spots on head and body ( Fig. 2b ). Some light marbling lines on gular area. Dorsal, caudal, and anal fins translucent with slight whitish iridescence and numerous, conspicuous, large, black spots and blotches on dorsal and caudal fin, fewer on anal fin. Pectoral fin with basal blotch and three lighter, beige bands alternating with two dark brown bands.

Small juveniles ( Fig. 2c ), 10–15 mm SL (just released from mouthbrooding parent upon capture) with light brown dorsum, bright yellowish midlateral band, darker brown ventral third of head and body, and translucent fins.

Geographical distribution. The species is so far only known from its type locality ( Figs. 4 , 5 ).

Etymology. The species name rara honours the Indian ichthyologist Rajeev Raghavan for his contributions to the elucidation of taxonomically difficult Indian freshwater fishes and their conservation; it is formed from the first two letters of his first name and surname. A noun in apposition.

Remarks. The type specimens were caught only at night after several juveniles, with their unique colour pattern, had been collected during daytime. One mouthbrooding male, which could not be collected, released young from its mouth, one of which is illustrated in Figure 2c . The stream from which Channa rara was collected during the dry season consisted of meandering streamlets separating and reconnecting along the course with intermittent island-like areas ( Fig. 4 ). The ground was rocky, sometimes with gravel-covered or sandy sections. Water was clear and the water level ranged from 10 cm to 0.5 m. All type specimens were collected along the banks, where they hid among roots and terrestrial vegetation that hung into the water. Co-occurring fish species included: Devario malabaricus , Schismatogobius deraniyagalai , Ompok sp., Paracanthocobitis mooreh , Pethia lutea , Rasbora dandia , Etroplus suratensis , Dawkinsia cf. filamentosa , Aplocheilus lineatus , Salmostoma boopis , and Schistura sp.

Genetic analysis. Channa rara differs from topotypic Channa gachua by an uncorrected p genetic distance of 9.7%, and by 8.6% from topotypic Ophicephalus marginatus in COI partial gene sequence.

Figures

FIGURE 1. Channa rara, BNHS FWF 1003, holotype, 87.6 mm SL, India: Maharashthra: Jagbudi River near Khopi Village.

FIGURE 2. Channa rara, live colouration. (A) BNHS FWF 1003, holotype, 87.6 mm SL, India: Maharashthra: Jagbudi River near Khopi Village, note series of small dark spots along base of dorsal fin, large ocellus-like blotch at posterior dorsal fin. (B) juvenile, not preserved, ca. 30 mm SL, note numerous black blotches in dorsal, anal, and caudal fins. (C) small juvenile released from mouthbrooding male, not preserved, ca. 12 mm SL.

FIGURE 3. Channa rara, variation of live colouration. (A) BNHS FWF 1004-1005, paratypes, 90.3 mm SL (left) and 82.1 (right), note presence of two (left) and three (right) posterior ocellus-like dorsal-fin blotches. (B) BNHS FWF 1004-1005, paratypes, 90.3 mm SL (left) and 82.1 (right) illustrating ventral head colouration.

FIGURE 4. Map illustrating collecting locality of Channa rara in southern Peninsular India.

FIGURE 5. Type locality of Channa rara, India: Maharashtra: Ratnagiri District: Jagbudi River, illustrating separating and reconnecting meandering streamlets.