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Accepted: 03 September 2021; Published: 7 October 2021
FishTaxa (2021) 21: 19-27
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Aborichthys palinensis, a new species of river loach (Cypriniformes: Nemacheilidae) from
Arunachal Pradesh, Eastern Himalaya, India
Prasanta NANDA1, , Lakpa TAMANG2,
Department of Zoology, Dera Natung Govt College, Itanagar, Arunachal Pradesh, India.
Fisheries and Aquatic Ecology Laboratory, Department of Zoology, Rajiv Gandhi University, Rono Hills, Doimukh, Itanagar, Arunachal Pradesh-
791112, India.
⁕Corresponding author: lakpatamang@rediffmail.com
Abstract
A new species of nemachilid loach is described based on four adult specimens (90.9-102 mm SL) from a tributary of the Palin River, in
Arunachal Pradesh, northeastern India. The new species differs from all congeners by the following combination of characters: dorsal and
ventral adipose crest absent, the presence of 5 rows of brown spots across dorsal fin; vent closer to the caudal-fin base (44.1-45.6% SL)
than to the snout tip (52-55% SL); caudal fin broadly rounded with two concentric bars; 30-35 regular and narrow oblique stripes along
the flank except anterior most part. Further can be distinguished on the following characters: pre-dorsal length (46.7-49.7% SL); pre-
pectoral length (18.5-18.7% SL); pre-pelvic (length 43.1-46.2% SL); caudal fin (length 14.7-16.9% SL); dorsal to pectoral distance (30.5-
33.2% SL); dorsal to caudal base distance (49.1-52.8% SL); dorsal to anal distance (28.4-33.0% SL); pectoral to anal distance (54.2-61.6%
SL); anal to caudal base distance (23.6-24.9% SL); and eye diameter (8.0-11.0% HL).
Keywords: Cypriniformes, Palin River, Eastern Himalaya, Brahmaputra River, Western Arunachal.
Zoobank: urn:lsid:zoobank.org:pub:C5211CED-510F-438C-8C3A-1735BD9DDF34
Zoobank: urn:lsid:zoobank.org:act:3669736A-54F6-482A-AE02-1E69B0D07D52
Citation: Nanda P., Tamang L. 2021. Aborichthys palinensis, a new species of river loach (Cypriniformes: Nemacheilidae) from
Arunachal Pradesh, Eastern Himalaya, India. FishTaxa 21: 19-27.
Introduction
The nemachilid loaches of the genus Aborichthys are characterized by having an elongate and slender body
almost of parallel profiles consisting of minimal 12-16 and maximum 33-35 oblique bars along flank, more or
less rounded to emarginated caudal fin; horizontally placed paired fins; pelvic fins extending beyond the vent;
vent closer to snout tip, caudal-fin base or almost middle of body; two black ocellus– one on upper sub-distal
basicaudal bar and another at dorsal-fin origin, and all fins considerably separated (Chaudhuri 1913; Hora 1921,
1925; Kottelat 1990) and presence of dorsal and ventral adipose crest in some species (Kosygin et al. 2019;
Shangningam et al. 2019). They are well-adapted in moderate to fast flowing rivers, streams and hill drainages
comprises of gravelly substrate (Hora 1925).
The genus Aborichthys was first erected by Chaudhuri (1913) assigning A. kempi as type species, collected
by S.W. Kemp from Sirpo and Egar streams near Rottung and Renging villages, Arunachal Pradesh on the east.
The genus Aborichthys has since been remained monotypic until Hora (1921) described A. elongatus from the
Riang River (Brahmaputra basin), Darjeeling (West Bengal) on the west. Subsequently Hora (1925) further
described A. garoensis from Tura, Garo Hills, Assam (now Meghalaya) in the south, followed by Barman (1984)
who added fourth species A. tikaderi from Namdapha Wildlife Sanctuary, Changlang District in the most
southeastern part of the state Arunachal Pradesh. Moreover, over a time span of six years, six more species have
been recognized from the upper Brahmaputra River basins in Arunachal Pradesh viz. A. waikhomi Kosygin,
2012, from Bulbulia stream near Bulbulia, a tributary of Noa-Dihing river, Namdapha, Changlang District in
the east; A. cataracta and A. verticauda Arunachalam et al., 2014 from a tributary of Ranga River, A. kailasi,
A. pangensis Shangningam et al., 2019 from the Pange River, Ziro, Lower Subansiri district in the west;
A. iphipaniensis Kosygin et al., 2019 from the Iphipani River, Roing, Lower Dibang Valley District in the east;
and A. boutanensis (Griffith and McClelland 1842) from neighboring country Bhutan originally named as
Cobitis boutanensis Griffithi and McClelland 1842 followed by Paracobitis boutanensis (Griffithi and
20
FISHTAXA (2021) 21: 19-27
McClelland 1842) in Eschmeyer (2020). Later, Thoni and Hart (2015) placed the P. boutanensis as the species
of Aborichthys and consequently considered A. kempi as a junior synonym of A. boutanensis, based on shared
morphological characters except body depth. However, Shangningam et al. (2019) has revalidated A. kempi
based on examining type specimens housed in ZSI, Kolkata, India. Including the currently described species,
there are twelve species of Aborichthys, whose diversity mostly confined to Brahmaputra River basin in
Arunachal Pradesh in North eastern India and the distribution extends to Bhutan and upper Myanmar (Chaudhuri
1913; Chaudhuri 1919; Hora 1925; Talwar and Jhingran 1991; Shangningam et al. 2019). While conducting
ichthyological surveys of Palin River at Palin in Western Arunachal Pradesh, four specimens of Aborichthys
were collected. Further examination of those specimens revealed that it belongs to an undescribed one, which
is described herein.
Material and Methods
Samplings of fishes were carried out by using caste net with (2 m diameter and 7 mm meshes). Fishes were
freshly preserved in 10% formaldehyde in the beginning and then stored in 70% ethanol. The morphometric
measurements were recorded point to point with digital calipers nearest to 0.01mm. Counts and measurements
were made on the left side of specimens following Kottelat (1990) and Arunachalam et al. (2014). Subunits of
head are expressed as proportions of lateral head length. Fin rays, sensory pores on head and lateral line were
counted under a stereo-zoom transmitted light microscope. Asterisk mark (*) after meristic value wherever
present indicates for holotype. The holotype is deposited in Zoological Survey of India (ZSI), Estuarine Biology
Regional Centre (EBRC), Gopalpur, Orissa and paratypes (3) in the Museum of Dera Natung Govt. College
(DNGC), Itanagar respectively for future reference.
Results
Aborichthys palinensis, sp. nov.
(Fig. 1, Table 1)
Holotype: EBRC/ZSI/F-12609, 102 mm SL; holotype, a tributary of Palin River (27°43'21.65"N,
93°38'47.48"E), 840 m asl, upper Brahmaputra River basin, Kra Daadi District, Arunachal Pradesh; India, G.
Ako. 26 February 2017.
Paratypes: DNGC F-04, 3, 90.9-97.5 mm SL, same as holotype.
Diagnosis: The new species is diagnosed from its congeners by the following combination of characters: dorsal
and ventral adipose crest absent, presence of 5 rows of brown spots across dorsal fin, each three rows of spots
from base confluent to each other; vent closer to caudal-fin base (44.1-45.6% SL) than to snout tip (52-55%
SL); caudal fin broadly rounded with two concentric bars; 30-35 regular and narrow oblique stripes along flank
except anterior most part. Further can be distinguished by following characters: pre-dorsal length (46.7-49.7%
SL), pre-pectoral length (18.5-18.7% SL), pre-pelvic (length 43.1-46.2% SL), caudal fin length (14.7-16.9%
SL), dorsal to pectoral distance (30.5-33.2% SL), dorsal to caudal base distance (49.1-52.8% SL), dorsal to anal
distance (28.4-33.0% SL), pectoral to anal distance (54.2-61.6% SL), anal to caudal base distance (23.6-24.9%
SL), and eye diameter (8.0-11.0% HL).
Description: For general appearance see Figure 1. Morphometric data are presented in Table 1. Body elongate
and slender, body between pectoral fin and posterior tip of dorsal fin cylindrical and thereafter greatly
compressing to caudal-fin base, body deepest at dorsal-fin origin, little bit deeper than wide. Dorsal profile
evenly rising from snout tip to occiput, thereafter almost horizontal to caudal-fin base. Ventral profile almost
horizontal to anal-fin origin, then gently rising up to posterior end, thereafter very gently decreasing to caudal-
fin base. Body profiles almost parallel.
21
Nanda and Tamang - Aborichthys palinensis, a new species of river loach from India
Figure 1.
Aborichthys palinensis, EBRC/ZSI/F-12609, holotype, 102.0 mm SL, a tributary of Palin River, Arunachal Pradesh, showing dorsal,
lateral and ventral views; lateral view showing thin and regular oblique stripes; ventral view showing vent situated closer to caudal-fin base than
snout tip.
Figure 2.
Aborichthys palinensis, EBRC/ZSI/F-12609, holotype, 102.0 mm SL, a tributary of Palin River, Arunachal Pradesh, dorsal and ventral
views of head, a, showing rounded snout; and b, cashew-nut shaped mouth.
22
FISHTAXA (2021) 21: 19-27
Head moderate and depressed, longer than broad, dorsal outline very gently sloping up to occiput and ventral
flattened. Snout obtusely rounded and triangular when viewed dorsally. Occipital margin W-shaped. Mouth
inferior, crescentic and surrounded by soft, thick, fleshy and pleated lips, wider than long, and surrounded by a
deep furrow behind (Fig. 2b). Upper lip with minute median incision. Lower lip with two large roughly
triangular pads or knobs separated by an extremely narrow median interruption. Processus dentiformes
prominent and situated in the middle of mouth.
Three pairs of barbels: One pair maxillary and two pairs of rostral, larger than eye. Inner rostral barbel
reaching posterior margin of knob of lower lip, but not reaching base of maxillary barbel, whereas outer rostral
barbel reaching maxillary barbel base, maxillary barbel at vertical almost reaching to middle of eye. Eyes
moderate, situated dorsally, invisible ventrally, slightly closer to snout tip than to posterior extremity of opercle,
separated by a broad interorbital space. Nostril closer to eye than to tip of snout, nares separated by triangular
membrane flap dividing it into two parts, anterior nare tubular and attached with membrane flap, flaps with
broad base and pointed tip, sometime twisted; posterior nare elongate. Vent situated very closer to pelvic-fin
origin (27.8-31.7% of pelvic to anal-fin origin) than anal-fin origin (65.0-68.7% of pelvic to anal-fin origin),
and closer to caudal-fin base (44.1-45.6% SL) than snout tip (52-55% SL).
Body embedded with minute cycloid scales, absent on ventral surface between isthmus and level of pectoral-
fin origin. Lateral line incomplete, 31-40 pores extending mostly before pelvic-fin, sometime to its origin with
considerably a broad interruption. Flank with 30-35 thin oblique stripes, mostly regular and equal sized except
anterior bars, interspace little bit broader than bar.
Dorsal fin with 2 simple and 8 branched rays, last ray weakly branched and originating from same
pterygiophore, situated at vertical almost in between pectoral fin- and anal-fin origins, at vertical slightly
posterior to pelvic-fin origin and 0.1-4.3% SL nearer to snout tip than to caudal-fin base, tip of last ray at vertical
exceed anal-fin tip, anterior and posterior margins straight and distal slightly arched, second or third branched
ray the longest, and length of dorsal and anal fins almost equal. Dorsal to pectoral equals occiput to pelvic
distance; dorsal to anal equals pelvic to anal distance; and dorsal to pectoral almost equals dorsal to anal distance.
Pectoral fin broad leaf-shaped, with i11*, i9i (1), i10i (1) rays, tip obtusely pointed with three patterns of
rays– first ray unbranched, second ray single branched, third ray (unbranched+ single branched i.e trifurcate),
and rest double branched (tetrafurcate) except the last unbranched ray in case of paratypes; fourth or fifth
branched ray the longest, anterior margin slightly convex, distal obtusely rounded; its tip extending to middle
of pectoral- and pelvic-fin origins.
Pelvic fin broad leaf-shaped with i7 rays, tip obtusely pointed with three patterns of rays– first ray
unbranched, second ray single branched, third ray (unbranched + single branched i.e trifurcate), rest double
branched (tetrafurcate) except last weak single branched ray, its last shortest ray slightly exceeding vent; pelvic
fin situated at vertical slightly anterior to dorsal-fin origin, closer to pectoral fin (26.0-28.1% SL) than anal-fin
(28.4-32.0% SL) origins. Pelvic-fin base with a small fleshy axillary lobe behind, not exceeding posterior end
of base. Anal fin leaf-shaped, but narrower than pectoral and pelvic fins, with ii5*, ii5i (3) rays, anterior margin
slightly convex and distal moderately arched; first two rays unbranched, second ray single branched, third (first
unbranched+second branched, i.e. trifurcate), rest double branched (tetrafurcate) and last single branched in
holotype and unbranched in paratypes. Its tip separated by a distance of 11.3-12.4%SL from caudal-fin base.
Caudal fin broadly rounded with i16i*(2), i17i (2) segmented rays, first upper and lower ray shortest, fin deepest
at posterior end. Caudal peduncle (1.6-1.8) times longer than depth (56.5-64.1% of caudal peduncle length).
Caudal peduncle length (17.5-18.7% SL) almost equals pre-pectoral length (18.5-18.7% SL) and caudal fin
shorter (14.7-16.9% SL) than head length (18.4-19.2% SL).
23
Nanda and Tamang - Aborichthys palinensis, a new species of river loach from India
Table 1. Morphometric data of Aborichthys palinensis (n=4). Range, mean and SD includes values of holotype
Holotype
Range
Mean±SD
Standard length (mm)
102
90.9-102
96.7±4.6
% Standard Length
Heal length
18.4
18.4-19.2
18.9±0.3
Head width
11.7
11.7-12.8
12.3±0.5
Head depth
8.4
8.1-8.8
8.5±0.3
Body depth at dorsal-fin origin
11.3
11.3-12.1
11.6±0.4
Body width at dorsal-fin origin
9.9
9.9-11.5
10.5±0.7
Predorsal length
46.7
46.7-49.7
48.5±1.3
Prepectoral length
18.6
18.5-18.7
18.6±0.1
Prepelvic length
43.1
43.1-46.2
44.8±1.3
Preanal length
71.7
71.7-77.6
75.3±2.5
Preoccipital length
14.7
14.5-16.7
15.2±1.0
Pectoral-fin length
12.7
12.7-13.8
13.4±0.4
Dorsal-fin length
12.4
11.5-13.8
12.8±1.1
Dorsal-fin base length
9.0
9.0-10.9
9.9±0.9
Pelvic-fin length
10.8
10.8-12.3
11.7±0.7
Pelvic-fin base length
2.9
2.9-3.9
3.3±0.4
Anal-fin length
11.8
11.8-12.7
12.1±0.4
Anal-fin base length
5.9
5.1-5.9
5.4±0.3
Caudal-fin length
14.7
14.7-16.9
15.9±1.0
Caudal peduncle length
17.7
17.5-18.7
18.1±0.6
Caudal peduncle depth
10.0
10.0-12.0
11.0±0.8
Occiput to dorsal-fin origin
32.4
32.4-33.7
32.9±0.6
Occiput to pelvic-fin origin
30.5
30.5-33.2
31.9±1.4
Dorsal to pectoral-fin origin
30.5
30.5-33.2
32.4±1.3
Dorsal to anal-fin origin
28.4
28.4-33.0
31.2±2.2
Dorsal-fin origin to caudal-fin base
51.0
49.1-52.8
50.8±1.6
Pectoral to pelvic-fin origin
26.0
26.0-28.1
27.2±1.0
Pectoral to anal-fin origin
54.2
54.2-61.6
58.1±3.0
Pelvic origin to anal-fin origin
28.4
28.4-32.0
30.6±1.5
Pectoral-fin origin to vent
35.3
35.3-38.8
37.2±1.4
Pelvic-fin origin to vent
9.0
8.9-9.3
9.1±0.2
Vent to anal-fin origin
19.5
19.5-22.0
20.5±1.1
Snout tip to vent
52.0
52.0-55.0
54.1±1.4
Vent to caudal-fin base
44.1
44.1-45.6
45.1±0.7
Anal-fin origin to caudal-fin base
24.5
23.6-24.9
24.3±0.5
Tip of anal-fin to caudal-fin base
11.3
11.3-12.4
11.8±0.6
% of Pelvic to anal-fin origin
Vent to anal-fin origin
68.6
65.0-68.7
67.2±1.8
Vent to pelvic-fin origin
31.7
27.8-31.7
29.9±1.6
% of head length
Head depth
45.7
42.2-46.2
45.0±1.9
Upper jaw length
31.9
31.8-32.4
32.1±0.3
Lower jaw length
22.3
22.3-26.0
24.0±1.6
Snout length
42.6
42.6-45.9
43.9±1.5
Prenasal length
29.3
27.0-29.7
28.7±1.2
Eye diameter
8.0
8.0-11.0
9.5±1.4
Inter-orbital width
26.3
24.3-27.0
25.9±1.1
Inter-narial width
13.3
13.3-17.8
15.6±1.9
Head width
63.3
59.5-67.6
63.8±3.4
Gape width
37.2
31.8-37.2
34.1±2.3
Lower jaw to isthmus
39.9
32.4-39.9
36.4±3.2
Head depth at nostril
33.0
32.4-34.7
33.1±1.1
Head depth at pupil
37.2
37.2-43.2
39.7±2.7
Inner rostral barbel length
22.9
21.6-24.3
22.8±1.1
Outer rostral barbel length
20.2
17.3-27.0
21.6±4.1
Maxillary barbel length
17.0
16.2-18.5
17.0±1.1
Ratio
Caudal peduncle length/caudal peduncle
1.8
1.6-1.8
1.7±0.1
% Caudal peduncle length
Caudal peduncle depth 56.5 56.5-64.1 60.7±3.8
24
FISHTAXA (2021) 21: 19-27
Color in preservative: In 70% ethanol, body background beige with light brown oblique bars. Dorsum of head,
scattered spots and irregular marks dark brown except light beige cheek region. Ventral region up to pelvic fin
creamy, a light brown longitudinal median strip between vent and anal fin, and between anal and caudal fin
base. Inter-radial membranes of dorsal, pectoral, pelvic and anal fins hyaline and radial semi hyaline. Caudal
fin with two concentric bars– first subdistal bar dark brown, narrow, equal sized, and broadly rounded, second
bar oval shaped, its anterior margin light brown, posterior region dusky, appears as broad patch, both bars
interrupted by a broad interspace in between (Fig 3a), rest hyaline to semi-hyaline. A dark brown spot on upper
margin of caudal-fin base. Dorsal fin with 5 rows of brown spots existing on each radial and one dark brown
ocellus at its origin; first and second rows from the top separate, whereas third, fourth and fifth rows confluent
(Fig. 3b).
Distribution and habitat: Till date, Aborichthys palinensis is only known from a small tributary of Palin River
at Palin town in western Arunachal. It flows towards east about 5 km and merged with Kurung river (Fig. 4).
Kurung River further moves about 30 km towards east and confluence with Kumey River from Palin town.
Confluence of two Rivers is popularly known as “Kurung-Kumey”. Further it flows southeast and finally merges
with Subansiri River in the lower reach, which is a major tributary of upper Brahmaputra River. River bed
comprised of medium sized boulders, and mixture of pebbles, cobbles, sand and large boulders somewhere.
Water was cool, clear and moderate to fast flowing. Riparian vegetation comprises of grasses, shrubs and small
to medium sized trees along the banks and larger trees towards uphill. Along with the collections other species
collected were; Oreoglanis, Pseudecheneis, Schizothorax, Exostoma, Garra, Neolissocheilus and Channa.
Figure 3. Aborichthys palinensis, DNGC F 04, paratype, 90.9 mm SL, a tributary of Palin River, Arunachal Pradesh; a, showing broadly rounded
caudal fin; b, EBRC/ZSI/F-12609, holotype, 102.0 mm SL, a tributary of Palin River, dorsal fin showing five rows of brown spots, three spots
from base confluent to each other (part of thumb seen anteriorly, aided in spreading fin).
Figure 4.
Map of Arunachal Pradesh, showing type
locality of Aborichthys palinensis (filled circle).
a
b
25
Nanda and Tamang - Aborichthys palinensis, a new species of river loach from India
Etymology: The species name ‘palinensis’ is assigned after the name of the area ‘Palin’ headquarter of Kra
Daadi District, where the fish was obtained.
Discussion
The genus Aborichthys exhibits three different positions of vent i.e. closer to snout tip, closer to the caudal-fin
base, and almost in the middle of the body which is used as a generic character to differentiate other nemacheilid
genera and among species as well (Hora, 1925; Kottelat 1990; Kosygin, 2019). Aborichthys palinensis belongs
to the above second category in being the vent closer to the caudal-fin base than to the snout tip. Among the
eleven known species of Aborichthys, the new species closely shares with A. kailashi in overall general
appearance, shares primarily the narrow and regular oblique stripes along the flank except anterior ones, shape
of head in dorsal view, maximum number of oblique bars (35 in A. palinensis and 36 in A. kailashi), dorsal-fin
length (11.3-13.8 in A palinensis and 11.3-13.4 in A. kailashi % SL), pelvic-fin length (11.5-12.3 in A. palinensis
and 10.9-12.4 in A. kailashi % SL), distance between vent to anal-fin origin (20.2-22.0 in A. palinensis and 20.2-
24.7 in A. kailashi % SL), inter-orbital space (24.3-27.0 in A. palinensis and 25.0-28.0 in A. kailashi % HL),
eye diameter (8.6-11.0 and 8-10 in A. kailashi % HL). Moreover, to some extent, the type locality (Palin river),
shares with, in being the same geographical area, ranging about 87 km apart from the Pange river (type locality
of A. kailashi) in the northwest, but unconnected river system and varied altitudes (840 m vs. 1600 m asl). Pange
river flows west-south direction and meet with Ranga River in lower reach, whereas Palin river moves towards
eastern direction after confluence Kurung River and confluences with the Kumey River, which eventually joins
with the Subansiri River in the southeast. Despite, A. palinensis differs from A. kailashi by having mouth
moderately (vs. widely) arched, lacking (vs. having) dorsal and ventral adipose crest, a broadly round (vs. oval)
shaped caudal fin, its distal band narrow and light brown (vs. broad and black (Fig. 2b), Shangningam et al.,
2019; fig. 2). Further can be differentiated by having 5 (vs. 2) rows of spots on dorsal fin; a deeper body (11.3-
12.1 vs. 7.5-9.2% SL); a greater pre-dorsal (length 46.7-49.7 vs. 40.7-46.2% SL); a shorter caudal peduncle
(length 17.5-18.7 vs. 18.5-21.6% SL) and deeper caudal peduncle (56.5-64.1 vs. 46-55% of caudal peduncle
length).
Aborichthys palinensis is distinguished from A. iphipaniensis by having considerably a narrower (vs. wider)
interspaces between oblique bars along the flank; a higher body (11.3-12.1 vs. 8.9-9.9% SL); a longer pre-dorsal
(46.7-49.7 vs. 42.4-44.4% SL) and pre-pelvic (43.1-46.2 vs. 39.4−42.0% SL); a shorter caudal peduncle (17.5-
18.7 vs. 21.5-23.3% SL), vent to anal distance (19.5-22.0 vs. 24.1-27.5% SL) and to caudal base (44.1-45.6 vs.
52.0-56.2% SL) and from A. waikhomi in having the snout obtusely (vs. sub obtusely) blunt, a shorter pre-pelvic
(43.1-46.2 vs. 46.1-50.0% SL), and a smaller eye (8.0-11.0 vs. 14.1-17.8% HL).
Aborichthys palinensis is distinguished from A. pangensis by having the snout obtusely blunt (vs. obtusely
pointed), a deeper body (11.3-12.1 vs. 10.1-11.2% SL); a shorter head (18.4-19.2 vs. 20.6-21.4% SL), pre-pelvic
(43.1-46.2 vs. 48.1-50.0% SL), pre-pectoral (18.5-18.7 vs. 19.6-21.4% SL, caudal fin (14.7-16.9 vs. 17.5-18.7%
SL), anal fin (11.8-12.7 vs. 13.6-14.7% SL) and pelvic fin (10.8-12.3 vs. 13.1-15.6% SL); a longer caudal
peduncle (17.5-18.7 vs. 16.0-17.5% SL); and a smaller eye (8.0-11.0 vs. 15-18% HL); from A. verticauda in
having a shorter pre-pectoral (18.5-18.7 vs. 20.0-24.2% SL), pre-pelvic (43.1-46.2 vs. 48.0-53.2% SL) and snout
to vent distance (52.0-55.0 vs. 56.7-61.4% SL); a longer caudal peduncle (17.5-18.7 vs. 11.0-16.6% SL); a
greater dorsal to caudal base distance (49.1-52.8 vs. 36.5-41.4% SL); and a smaller eye (8.0-11.0 vs. 14.0-20.5%
HL).
Aborichthys palinensis is further distinguished from A. waikhomi, A. pangensis and A. verticauda in having
broadly a rounded (vs. truncate) caudal fin with two smoothly arched bars (vs. several irregular black blotches
in A. waikhomi; several irregular clusters of black spots in A. pangensis; and 4-5 irregular bars in A. verticauda).
26
FISHTAXA (2021) 21: 19-27
Aborichthys palinensis is distinguished from A. elongatus in having a shorter pre-pelvic (43.1-46.2 vs. 48.6-
49.9% SL); a greater dorsal to pectoral- (30.5-33.2 vs. 23.6-24.0% SL), dorsal to anal- (28.4-33.0 vs. 19.4-
21.6% SL), dorsal to caudal base- (49.1-52.8 vs. 31.6-37.2% SL) and pelvic to anal- (28.4-32.0 vs. 19.6-22.6%
SL) and vent to anal distance (19.5-22.0 vs. 12.9-15.0% SL); a shorter snout to vent- (52.0-55.0 vs. 60.2-71.8%
SL) and pectoral to pelvic distance (26.0-28.1 vs. 30.3-32.9% SL); and a smaller eye (8.0-11.0 vs. 15.5-22.8%
HL); from A. tikaderi in having a greater pre-dorsal (length 46.7-49.7 vs. 42.6-44.3% SL), pre-pectoral (18.5-
18.7 vs. 14.6-16.2% SL), pre-pelvic (43.1-46.2 vs. 37.8-41.4% SL), dorsal to pectoral distance (30.5-33.2 vs.
23.4-27.1% SL), and dorsal to anal distance (28.4-33.0 vs. 20.9-24.7% SL); a shorter caudal fin (14.7-16.9 vs.
20.2-21.2% SL) and anal to caudal base distance (23.6-24.9 vs. 24.9-27.4% SL); from A. garoensis in having a
longer caudal peduncle (length 17.5-18.7 vs. 14.3-16.1% SL); a greater dorsal to pectoral- (30.5-33.2 vs. 22.6-
25.9% SL), dorsal to caudal base- (49.1-52.8 vs. 40.2-41.5% SL), anal to caudal base- (23.6-24.9 vs. 14.1-14.7%
SL) and snout to vent distance (52.0-55.0 vs. 48.5-50.6% SL); a longer pre-dorsal (length 46.7-49.7 vs. 41.7-
43.8% SL), pre-pectoral (length 18.5-18.7 vs. 15.3-15.8% SL) and pre-pelvic (length 43.1-46.2 vs. 40.4-41%
SL); and a shorter caudal fin (length 14.7-16.9 vs. 20.6-21.90% SL); from A. kempi in having a shorter pre-
pectoral (length 18.5-18.7 vs. 19.7-20.2% SL), caudal fin (length 14.7-16.9 vs. 19.6-22.4% SL), pectoral to anal-
(54.2-61.6 vs. 51.3-54.0% SL) and anal to caudal base distance (23.6-24.9 vs. 25.2-27.0% SL); a greater dorsal
to anal-(28.4-33.0 vs. 24.7-26.8% SL), dorsal to caudal base- (49.1-52.8 vs. 39.6-42.5% SL) and pelvic to anal
distance (28.4-32.0 vs. 26.6-26.9% SL); and a smaller eye (8.0-11.0 vs. 14.9-17.0% HL); from A. cataracta in
having a shorter caudal fin (14.7-16.9 vs. 19.4-21.9% SL); a greater dorsal to pectoral- (30.5-33.2 vs. 24.7-
28.0% SL), dorsal to anal- (28.4-33.0 vs. 23.0-28.1% SL), and dorsal to caudal base distance (49.1-52.8 vs.
39.0-46.0% SL); a smaller eye (8.0-11.0 vs. 13.4-17.9% HL).
Aborichthys palinensis is further distinguished from A. kempi, A. elongatus, A. garoensis, A. tikaderi,
A. cataracta, A. pangensis and A. verticauda in lacking (vs. having prominent; shallow in A. elongatus,
A. tikaderi, A. cataracta, A. verticauda and A. pangensis) dorsal and ventral adipose crest (Shangingam et al
2019). Further it differs from A. kempi, A. garoensis and A. tikaderiby having the vent closer to the caudal-fin
base than to the snout tip (vs. closer to the snout tip than to the caudal-fin base); in addition to A. boutanensis,
further differs from A. kempi, A. tikaderi and A. waikhomi in having more oblique stripes along flank (30-35 vs.
27 in A. boutanensis (counted from the figure 1b in Thoni and Hart, 2015); 20-23 in A kempi; 16 in A. tikaderi;
and 12-16 in A. waikhomi); further from A. boutanensis in having fewer branched pectoral fin rays (9-11 vs.
12); fewer pelvic fin branched rays (7 vs. 8), a longer pectoral fin (12.7-13.8 vs. 15% SL); a shorter caudal
peduncle (length 17.5-18.7 vs. 19% SL); in having more oblique bars along the flank (30-35 vs. ca 28).
Comparative materials: Aborichthys waikhomi: V/APRC/ZSI/P-519, paratypes, 2, 59.0-68.0 mm SL; Bulbulia
stream near Bulbulia, Namdapha, Arunachal Pradesh, J.K. De &team, 06 November 2009.
Aborichthys iphipaniensis: paratypes, ZSI/V/APRC/P-1659, paratypes, 3, 107.5-120.8 mm SL; Iphipani
River at Roing, Lower Dibang Valley, Brahmaputra River basin, Arunachal Pradesh, India, S. Devi and team,
04 April 2016.
Aborichthys kailashi: ZSI/V/APRC/P 786, paratypes, 4, 89-113 mm SL; Pange River at Arolenching, Ziro,
Lower Subansiri District: Brahmaputra basin, Arunachal Pradesh, Bikramjit Sinha and team, 09 Nov 2013.
Comparative data which could not be examined were accessed from the following literature sources:
Chaudhuri (1913), Kosygin (2012) and Arunachalam et al. (2014) for A. kempi, A. elongatus, A. tikaderi,
A. garoensis, A. waikhomi, A. cataracta and A. verticauda. Kosygin et al. (2019) for A. iphipaniensis (additional
data). Shangningam et al. (2019) for A. kailashi (additional data) and A. pangensis. Thoni and Hart (2015) for
A. boutanensis.
27
Nanda and Tamang - Aborichthys palinensis, a new species of river loach from India
Acknowledgement
We are grateful to Principal, DNGC, Itanagar for providing laboratory facilities. We are also thankful to Miss
G. Ako inhabitant of Palin for rendering her help in collecting of fish.
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