Amblyceps waikhomi, Darshan & Kachari & Dutta & Ganguly & Das, 2016

Darshan, Achom, Kachari, Akash, Dutta, Rashmi, Ganguly, Arijit & Das, Debangshu Narayan, 2016, Amblyceps waikhomi, a New Species of Catfish (Siluriformes: Amblycipitidae) from the Brahmaputra Drainage of Arunachal Pradesh, India, PLoS ONE (e 0147283) 11 (2), pp. 1-10 : 3-5

Amblyceps waikhomi sp. nov. ( Fig 1, S1 Fig) differs from all congeners in having a deeper body (depth at anus 17.0–20.3% SL vs. 7.6–16.9) and fewer (except A. mangois and A. serratum ) total vertebrae (34–35 vs. 37–48) (S1 Table). It differs from A. mangois in lacking (vs. having) strongly-developed projections on the proximal lepidotrichia of the median caudal-fin rays and in having a longer, wider, and deeper head (S2 Table) (length: 22.1–24.3% SL vs. 18.8– 21.3, width: 20.0–21.9% SL vs. 17.1–18.3, depth: 13.9–18.0% SL vs. 11.6–13.2); and from A. serratum in having a posteriorly smooth (vs. with 4–5 serrations) pectoral spine, and unequal jaw length (lower jaw longer and weakly-projecting anteriorly vs. equal upper and lower jaws). It additionally differs from A. murraystuarti , A. torrentis , A. apangi , A. laticeps , and A. cerinum in having a deeply forked (vs. emarginate or truncate) caudal fin.

Description

Morphometric data are shown in Table 1. Body short, stout, laterally compressed. Dorsal profile rising evenly from tip of snout to dorsal-fin origin, then straight upto middle of adipose-fin base, thereafter gently sloping ventrad to the end of caudal peduncle. Ventral profile convex up to anal opening, then gently sloping dorsally up to end of anal-fin base, thereafter gently sloping ventrad towards caudal-fin base. Anus and urogenital openings located slightly anterior to anal-fin origin.

Head depressed. Snout rounded. Mouth terminal with unequal jaws, lower slightly longer; lips papillate, with double fold of thickened skin. Premaxillary tooth band semicircular, bearing short, conical, posteriorly directed teeth. Mandibular teeth short, conical, arranged in narrow crescentic band. Eye small, rounded, and subcutaneous. Anterior nostril short, tubular, situated immediately anterior to base of nasal barbel. Nasal barbel extending beyond upper margin of upper gill opening, not reaching posterior margin of opercle. Maxillary and outer mandibular barbels reaching to base of last pectoral-fin ray. Inner mandibular barbel extending to base of pectoral-fin. Skin on head and body tuberculate. Lateral line incomplete, curved downward, and terminating at a point slightly anterior to vertical through dorsal-fin origin. First branchial arch with 2+7 (n = 5) gill rakers. Gill membranes narrowly joined at isthmus, with 10 (n = 2) branchiostegal rays.

Dorsal fin with a spinelet, a spine, and 6 (n = 5) branched rays; its origin closer to snout tip than to adipose-fin origin; posterior margin of fin convex; fin base fleshy and swollen. Dorsal-fin spine smooth, short and straight, distal tip sharply pointed, its length reaching one-third of fin height. Adipose fin short, low, commencing from vertical midway between anus and anal-fin origin, posterior margin well separated from caudal fin. Pectoral fin with a smooth spine and 6 (n = 5) branched rays; origin anterior to vertical through posterior margin of operculum posterior margin convex. Pectoral-fin spine longer than dorsal-fin spine, straight, anterior and posterior margins smooth. Skin covering pectoral-fin base and skin covering spine swollen. Pelvic fin with i–ii,4–5 rays, tip of adpressed fin reaching beyond urogenital opening but not anal-fin origin. Anal fin with iii,10 rays. Caudal fin deeply forked with i,7,8,i (n = 5) principal rays, simple-principal and segmented procurrent rays of upper and lower lobe bears pinnate like rays anteriorly, upper lobe longer than lower (S2 Fig).

Coloration. In 70% ethanol: Dorsal and lateral surfaces of head and body brownish, ventrally creamy.

Distribution. Presently known only from its type locality, Nongkon stream draining to Noa Dehing River (Brahmaputra basin), Namsai District, Arunachal Pradesh ( Fig 2).

Habitat. The new species was collected from a slow moving stream (water current 0.16 m / s) with a bottom substrate dominated by sand, occasionally associated with mud ( Fig 3). The species was often encountered under submerged logs and bamboo. Water hyacinth was the dominant macrophyte of the stream. Chemical parameters of the stream were DO 6.75 mg /l, DCO 2 1.53 mg /l, alkalinity 66.06 mg /l, and hardness 71.8 ± 3.05 mg /l; while the physical parameters were pH 6.78, air temperature 23.8 ±0.87°C, water temperature 23.5 ±0.96°C, transparency 79.5 ± 1.93 cm,and conductivity 173.33 μS.

Etymology. The new species is named after Waikhom Vishwanath, honouring his outstanding contribution to freshwater ichthyology in the Indian subcontinent.