Abstract
A new species of nemachilid loach Aborichthys barapensis, is described based on two adult specimens (91 and 97 mm SL) from the Barap Stream (a tributary of the Brahmaputra River basin) in the southeastern most part of the state of Arunachal Pradesh bordering Myanmar. The new species is distinguished from its congeners in having a narrow black basicaudal bar without a black ocellus on the upper end (vs. present); and in having a very low dorsal and ventral adipose crests (vs. prominent; absent in A. waikhomi). The new species is further distinguished from its congeners by the following combination of characters: body with 24–26 oblique bars along the flank; interspace narrower than bars on body; moderately rounded caudal fin with five distinct black to brown cross bars; vent closer to the caudal-fin base (44.1–45.1 % standard length) than to snout tip.
Highlights
Members of the genus Aborichthys belonging to family Nemacheilidae, is an elongate and slender bodied bottom dwelling freshwater loach, that inhabits fast flowing water of mountain rivers, streams, drainages of Ganga-Brahmaputra River, and is endemic to the eastern Himalaya
They are characterized by having vent situated close behind pectoral girdle, dorsal fin at vertical originated slightly behind pelvic fin-origin; narrow oblique bars on body; a black ocellus at upper extremity of caudal-fin base, and rounded or truncate caudal fin marked with concentric rings or irregular black patches, and all fins considerably separated (Chaudhuri 1913; Kosygin 2019; Shangningam 2019)
Nine species of Aborichthys are recognized as valid, whose diversity is mostly confined to Brahmaputra River basins in Arunachal Pradesh, northeastern India, and its distribution extends to Bhutan and Putao in Myanmar (Chaudhuri 1913, 1919; Hora 1925; Talwar & Jhingran 1991; Shangningam et al 2019)
Summary
Members of the genus Aborichthys belonging to family Nemacheilidae, is an elongate and slender bodied bottom dwelling freshwater loach, that inhabits fast flowing water of mountain rivers, streams, drainages of Ganga-Brahmaputra River, and is endemic to the eastern Himalaya. They are characterized by having vent situated close behind pectoral girdle, dorsal fin at vertical originated slightly behind pelvic fin-origin; narrow oblique bars on body; a black ocellus at upper extremity of caudal-fin base (but here absent), and rounded or truncate caudal fin marked with concentric rings or irregular black patches, and all fins considerably separated (Chaudhuri 1913; Kosygin 2019; Shangningam 2019). Over the last one decade, six more sympatric species have been described from the upper Brahmaputra River basins in Arunachal Pradesh, viz., Aborichthys waikhomi (Kosygin, 2012) from Bulbulia Stream near Bulbulia, a tributary of Noa-Dihing River, Namdapha, Changlang District in the east; A. kailasi and A. pangensis (Shangningam et al, 2019) from Pange River, Ziro, Lower Subansiri District in the west; and A. iphipaniensis (Kosygin et al, 2019) from Iphipani River, Roing, Lower Dibang Valley District in the east
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