JoTT PAPER
1(1): 02-08
Akysis portellus sp. nov., a new species of catfish
(Teleostei: Akysidae) from the Sittang River drainage, Myanmar
Heok Hee Ng
Raffles Museum of Biodiversity Research, Department of Biological Sciences, National University of Singapore, 6 Science Drive 2, # 03-01,
Singapore 117546
Email: dbsnhh@nus.edu.sg
Abstract: A second species of akysid catfish from the Sittang River drainage in Myanmar, Akysis portellus new species, is described in this
study. It can be distinguished from congeners (except for A. brachybarbatus, A. fuliginatus, A. manipurensis, A. pictus, A. pulvinatus, A.
prashadi, A. variegatus, A. varius, A. vespa and A. vespertinus) in having a smooth (vs. serrated) posterior edge of the pectoral spine. It is
distinguished from A. brachybarbatus, A. fuliginatus, A. manipurensis, A. pictus, A. prashadi, A. pulvinatus, A. variegatus, A. varius, A. vespa and
A. vespertinus in having a unique combination of: length of adipose-fin base 17.1–19.2% SL, caudal peduncle length 19.1–22.0% SL, caudal
peduncle depth 6.0–7.0% SL, gape width 9.5–11.1% HL, interorbital distance 30.8–36.8% HL, nasal barbel length 80.5–101.4% HL, maxillary
barbel length 116.7–143.2% HL, inner mandibular barbel length 53.7–79.2% HL, outer mandibular barbel length 101.1–127.8% HL and caudal
fin forked.
Keywords: Siluriformes, Sisoroidea, Sittang River, South Asia
Date of online publication 26 January 2009
ISSN 0974-7907 (online) | 0974-7893 (print)
Editor: Larry Page
Manuscript details:
Ms # o1913
Received 29 December 2007
Final revised received 25 November 2008
Finally accepted 26 November 2008
Citation: Ng, H.H. (2009). Akysis portellus, a
new species of catfish (Teleostei: Akysidae)
from the Sittang River drainage, Myanmar.
Journal of Threatened Taxa 1(1): 02-08.
Copyright: © H.H. Ng 2009. Creative Commons Attribution 3.0 Unported License. JoTT
allows unrestricted use of this article in any
medium for non-profit purposes, reproduction
and distribution by providing adequate credit
to the authors and the source of publication.
Author Details: HEOK HEE graduated with a
PhD from the University of Michigan in 2006
and has been working on the taxonomy of
Asian catfishes since 1994. Now at the Raffles
Museum of Biodiversity Research in
Singapore, his current research focus is on
sisoroid taxonomy and systematics.
Acknowledgements: I am grateful to Patrick
Yap for help in obtaining specimens of A.
portellus, and the following for permission to
examine material under their care: David
Catania (CAS), Maurice Kottelat (CMK), Sven
Kullander (NRM), Martien van Oijen (RMNH),
Douglas Nelson (UMMZ), Susan Jewett
(USNM), Isaäc Isbrücker (ZMA), Kelvin Lim
(ZRC) and A.K. Karmakar (ZSI). Financial
support by research grant R-154-000-318-112
of the National University of Singapore to
Heok Hui Tan is acknowledged.
INTRODUCTION
Akysid catfishes are small to medium-sized hillstream catfishes generally found in
fast-flowing streams and rivers in South and Southeast Asia. Members of the type
genus, Akysis, are small species (typically not larger than 50mm SL) with tuberculate skin
and a cryptic color pattern generally consisting of yellow patches or bands on a brown
body. They have a distribution ranging from the Irrawaddy River drainage to the west,
the Citarum River drainage to the east and south and the Lancanjiang (upper Mekong)
drainage to the north. The genus had been divided ino two species groups (the A.
variegatus and the A. pseudobagarius species groups) by Ng & Kottelat (1998), with members
of the A. pseudobagarius group being reassigned to the genus Pseudobagarius by Ferraris
(2007). There is considerable hidden diversity within the genus; more than half of the
20 valid species have been described in the last decade (Ng & Kottelat 1998, 2004; Ng
& Tan 1999; Arunkumar 2000; Ng & Freyhof 2003; Ng & Rainboth 2005; Ng 2006,
2007; Page et al. 2007).
Recently, specimens of Akysis collected from the Sittang River drainage in Myanmar
were made available to me. This material was initially identified as Akysis longifilis, but
close examination revealed enough differences to warrant its recognition as a distinct
species. The description of this new species as Akysis portellus sp. nov. forms the basis of
this study.
MATERIAL AND METHODS
Measurements were made point-to-point with dial calipers and recorded to 0.1mm.
Ng & Kottelat (1998) are followed for all measurements and counts, with the following
additions: dorsal-spine length, which is measured from the base to the tip of the dorsal
spine, head depth, which is measured at the base of the supraoccipital process (defined as
the posterior margin of the supraoccipital excluding the supraoccipital process), and
gape width, which is the horizontal distance of the mouth measured from one rictus to
another. Meristic values with an asterisk indicate those for the holotype.
Material examined in this study is deposited in the following institutions: Natural
History Museum, London (BMNH); California Academy of Sciences, San Francisco (CAS);
collection of Maurice Kottelat, Cornol (CMK); Naturhistoriska Riksmuseet, Stockholm
(NRM); Nationaal Natuurhistorisch Museum, Leiden (RMNH); University of Michigan
Museum of Zoology, Ann Arbor (UMMZ); National Museum of Natural History,
Washington DC (USNM); Zoölogisch Museum, Amsterdam (ZMA); Zoological Reference
Collection, Raffles Museum of Biodiversity Research, Singapore (ZRC); Zoological
Survey of India, Calcutta (ZSI).
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A new catfish Akysis portellus from Myanmar
Akysis portellus sp. nov.
(Images 1-5; Figure 1; Table 1)
Type material:
Holotype: ZRC 51138, 32.7mm SL; Myanmar: Bago
division, Shwe Kyin, 17o55N-96o53E; Than Kyaw Toe, August
2007.
Paratypes: NRM 57228 (5), 29.3-34.3mm SL; UMMZ
248469 (12), 23.8-33.8mm SL; ZRC 51139 (9), 28.9-35.0mm
SL; data as for holotype.
Non-type material: ZRC 46429 (15), 30.9-42.6mm SL;
Myanmar: from aquarium trade; H.H. Tan & H.H. Ng, 24 July
2001.
Diagnosis:
Akysis portellus sp. nov. is most similar to A. longifilis, which
occurs sympatrically in the Sittang River drainage. It is
distinguished from A. longifilis in having a shorter adipose-fin
base (17.1-19.2% SL vs. 25.7-31.1), smaller mouth (gape width
9.5-11.1% HL vs. 12.9-14.7; Image 2) and a more rounded
head shape when viewed dorsally (Image 3). Akysis portellus sp.
nov. differs from other congeners (except for A. brachybarbatus,
A. fuliginatus, A. longifilis, A. manipurensis, A. pictus, A. prashadi, A.
pulvinatus, A. variegatus, A. varius A. vespa and A. vespertinus) in
having a smooth (vs. serrated) posterior edge of the pectoral
spine. It is distinguished from A. brachybarbatus in having a
more slender caudal peduncle (6.0-7.0% SL vs. 7.9-8.1), from
A. fuliginatus in having a more slender caudal peduncle (6.07.0% SL vs. 10.1-10.5), longer nasal and maxillary barbels
(nasal barbel length 80.5-101.4% HL vs. 52.1-58.2; maxillary
barbel length 116.7-143.2% HL vs. 100.0-109.1), presence of
light saddle-shaped spots on the body (vs. uniformly dark body),
and a forked (vs. truncate) caudal fin, and from A. manipurensis
in having a more slender caudal peduncle (6.0-7.0% SL vs. 9.310.0) and longer nasal barbels (nasal barbel length 80.5-101.4%
HL vs. 68.9-89.4). Akysis portellus sp. nov. differs from A. pictus
in having a more slender caudal peduncle (6.0-7.0% SL vs. 7.78.5), shorter adipose-fin base (17.1-19.2% SL vs. 22.0-23.6),
and longer nasal and maxillary barbels (nasal barbel length
80.5-101.4% HL vs. 54.3-56.7; maxillary barbel length 116.7143.2% HL vs. 95.7-128.8), from A. prashadi in having a longer
caudal peduncle (19.1-22.0% SL vs. 16.5-18.4), and from A.
pulvinatus in having a shorter adipose-fin base (17.1-19.2% SL
vs. 23.0-25.2), more slender caudal peduncle (6.07.0% SL vs.
9.410.3), longer nasal and maxillary barbels (nasal barbel
length 80.5-101.4% HL vs. 13.9-57.5; maxillary barbel length
116.7143.2% HL vs. 78.5105.0). It is distinguished from A.
variegatus in having longer nasal and maxillary barbels (nasal
barbel length 80.5101.4% HL vs. 33.362.3; maxillary barbel
length 116.7143.2% HL vs. 78.3114.8), from A. varius in
having a forked (vs. truncate) caudal fin, from A. vespa in having
a more slender caudal peduncle (6.07.0% SL vs. 7.68.5), and
longer nasal and maxillary barbels (nasal barbel length 80.5
101.4% HL vs. 54.572.5; maxillary barbel length 116.7
143.2% HL vs. 89.098.2), and from A. vespertinus in having a
more slender caudal peduncle (6.07.0% SL vs. 7.49.2), larger
interorbital distance (30.836.8% HL vs. 24.528.8) and longer
barbels (nasal barbel length 80.5101.4% HL vs. 37.848.3;
maxillary barbel length 116.7143.2% HL vs. 84.996.6;
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H.H. Ng
inner mandibular barbel length 53.779.2% HL vs. 35.759.0;
outer mandibular barbel length 101.1127.8% HL vs. 66.3
83.1).
Description:
Biometric data in Table 1. Body moderately compressed.
Dorsal profile rising evenly but not steeply from tip of snout
to origin of dorsal fin, then sloping gently ventrally from there
to end of caudal peduncle. Ventral profile flat to anal-fin base,
then sloping gently dorsally from there to end of caudal
peduncle. Anus and urogenital openings located at vertical
through middle of adpressed pelvic fin. Skin tuberculate.
Lateral line extending just posterior to base of last anal-fin
ray. Vertebrae 16+16=32 (2), 17+15=32 (2), 16+17=33* (4)
or 17+16=33 (2).
Head depressed and broad, with rounded snout margin when
viewed from above. Anterior nostril tubular, base of nostril
not in contact with base of nasal barbel. Gill openings narrow,
extending from immediately ventral to posttemporal to onethird of distance from ventral midline of body to base of
pectoral spine. Bony elements of dorsal surface of head covered
with thick, tuberculate skin. Eye ovoid, horizontal axis longest;
located entirely in dorsal half of head.
Barbels in four pairs. Maxillary barbel long and slender,
extending to vertical through middle of dorsal-fin base. Nasal
barbel slender, extending to dorsalmost limit of gill opening.
Inner mandibular-barbel origin close to midline, extending to
base of pectoral spine. Outer mandibular barbel originating
posterolateral of inner mandibular barbel, extending beyond
base of last pectoral-fin ray.
Mouth subterminal, premaxillary tooth band not exposed
when mouth is closed. Oral teeth small and villiform, in
irregular rows on all tooth-bearing surfaces. Premaxillary tooth
band rounded, of equal width throughout. Dentary tooth band
much narrower than premaxillary tooth band at symphysis,
tapering laterally.
Dorsal fin located above anterior third of body, with I,4 (2),
I,4,i (6) or I,5* (2) rays; fin margin convex; spine short and
straight. Adipose fin with anterior margin slightly concave
and posterior margin angular, origin at vertical through middle
of pelvic-fin base. Caudal fin gently forked, with i,5,5,i (2) or
i,6,6,i* (8) principal rays; lower lobe slightly longer and broader
than upper lobe. Procurrent rays symmetrical and extending
only slightly anterior to fin base. Anal-fin origin at vertical
through approximately midpoint of adipose-fin base. Anal fin
with convex margin and iii,5,i* (6), iii,6 (1), iv,4,i (1) or iv,5 (2)
rays. Pelvic-fin origin at vertical through posterior end of
dorsal-fin base. Pelvic fin with slightly convex margin and i,5
(10) rays; tip of adpressed fin not reaching anal-fin origin.
Pectoral fin with I,6 (1), I,6,i (6) or I,7* (3) rays; fin margin
posteriorly convex; anterior spine margin smooth, posterior
margin without serrations.
Coloration:
In ethanol: dorsal surface and sides of head medium grayish
brown, with few darker brown spots randomly scattered
throughout. Dorsal surface and sides of body dark grayish
brown. Belly, chest and ventral surfaces of head and body
light brown. Dorsal half of body with two elongate saddleshaped light brown spots: first on body at anterior three-quarters
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A new catfish Akysis portellus from Myanmar
H.H. Ng
Image 1. Akysis portellus sp. nov., ZRC 51138, holotype, 32.7mm SL; dorsal, lateral and ventral views.
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A new catfish Akysis portellus from Myanmar
H.H. Ng
b
a
Image 2. Anterior views of: a - Akysis portellus sp. nov., ZRC 51139, paratype, 33.3mm SL; b - A. longifilis, ZRC 51157, 30.6mm
SL, showing differences in gape widths.
a
b
Image 3. Dorsal views of heads of: a - Akysis portellus sp. nov., ZRC 51139, paratype, 33.3mm SL; b - A. longifilis, ZRC 51157,
30.6mm SL, showing differences in shape.
Image 4. Akysis portellus sp. nov., ca. 31mm SL (specimen not preserved), showing live coloration.
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A new catfish Akysis portellus from Myanmar
H.H. Ng
Image 5. Akysis portellus sp. nov., UMMZ 248469, paratype, 30.4mm SL, showing orange hue present on head and body of
some individuals.
Table 1. Biometric data for Akysis portellus sp. nov. (n=10)
Holotype
Range
%SL
Predorsal length
Preanal length
Prepelvic length
Prepectoral length
Length of dorsal-fin base
Dorsal-spine length
Length of anal-fin base
Pelvic-fin length
Pectoral-fin length
Pectoral-spine length
Caudal-fin length
Length of adipose-fin base
Caudal peduncle length
Caudal peduncle depth
Body depth at anus
Head length
Head width
Head depth
35.2
64.8
45.6
23.2
14.1
13.1
14.7
15.0
22.6
15.0
21.1
18.7
20.8
7.0
15.3
23.9
22.6
14.4
33.8–38.1
64.0–69.2
45.6–51.4
20.1–23.2
12.6–14.1
13.1–15.9
12.7–15.6
12.9–15.0
22.0–24.5
14.3–16.3
20.5–24.8
17.1–19.2
19.1–22.0
6.0–7.0
12.0–15.3
21.8–27.0
22.6–26.7
14.4–17.4
36.1+1.5
66.5+1.9
48.2+2.5
21.7+1.2
13.4+0.7
13.9+1.1
14.6+1.1
13.8+0.8
23.2+0.9
15.5+0.7
22.8+1.8
17.9+0.9
20.6+1.3
6.7+0.4
13.6+1.1
24.7+1.7
24.4+1.5
15.9+1.3
%HL
Snout length
Gape width
Interorbital distance
Eye diameter
Nasal barbel length
Maxillary barbel length
Inner mandibular barbel length
Outer mandibular barbel length
39.7
9.5
30.8
10.3
89.7
143.2
59.4
110.3
31.7–40.3
9.5–11.1
30.8–36.8
8.8–12.5
80.5–101.4
116.7–143.2
53.7–79.2
101.1–127.8
37.0+3.9
10.0+0.6
34.2+2.3
10.3+1.3
89.4+7.4
127.3+9.8
65.3+10.3
113.1+8.7
Etymology:
From the Latin portella, the diminutive form of porta,
meaning door. The name is used as a noun and alludes to the
relatively small mouth of this species.
Distribution:
Known from the type locality in the Sittang River drainage,
southern Myanmar (Image 1).
D ISCUSSION
of adipose-fin base, second more elongate and between
posterior fifth of adipose-fin base and caudal flexure. Ventral
half of body with two similar saddle-shaped, light brown spots:
first between anal and pelvic fins and second between posterior
base of anal fin and caudal flexure. Anterior ventral spot
largely coalescent with light brown coloration of ventral
surfaces. Proximal two thirds of dorsal fin chocolate brown.
Anal and pelvic fins hyaline. Proximal half of pectoral fin
with reticulate brown band; rest of fin hyaline. Caudal fin
chocolate brown with distal one third of both upper and lower
lobes with large, mostly hyaline spot (with scattered
melanophores). Adipose fin dark grayish brown, except where
lighter brown saddles-shaped spots on body run through fin.
Barbels light brown, maxillary pair sometimes with few brown
rings proximally. Color in life similar, but more yellowishbrown overall (Image 4). Some individuals with marked orange
06
hue over dorsal surfaces of head and body (Image 5)
Mean+SD
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Five other species of Akysis are recorded from Myanmar
(Ng 2008): A. longifilis, A. pictus, A. prashadi, A. vespa and A.
vespertinus with a sixth species, A. manipurensis, being known
from the Chindwin River drainage (itself part of the Irrawaddy
River drainage) in India (Vishwanath et al. 2007). Only A.
longifilis is known to occur sympatrically with A. portellus sp.
nov. in the Sittang River drainage (the type locality of A. portellus
is about 90km downstream along the Sittang River from that
of A. longifilis; Image 1). Although both species are superficially
very similar, a side-by-side comparison reveals the differences
outlined in the diagnosis. These differences in the gross
morphology are not due to sexual dimorphism because the
differences are consistent across members of both species.
Although it cannot be excluded that the differences reflect
different geographical variants of the same species, the highly
distinct degree of difference in the shapes of the head and the
mouth makes it unlikely that consistent morphological
differences of this nature are merely due to geographical
variation. Furthermore, the caudal peduncle of A. portellus
appears to be more slender than that of A. longifilis, although
this difference is not translated measurably (caudal peduncle
depth 6.07.0% SL in A. portellus sp. nov. vs. 5.67.2 in A.
longifilis). There also appear to be slight differences in color
between the two species: the pelvic and anal fins of all A. portellus
specimens examined appear to lack any markings, while those
of A. longifilis usually have very few brown spots that form
indistinct transverse bands through the middle of the fins.
Finally, A. portellus sp. nov. has fewer vertebrae than A. longifilis
(3233 vs. 3335), although the overlap in vertebral counts
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A new catfish Akysis portellus from Myanmar
H.H. Ng
Figure 1. Type localities of Akysis portellus sp. nov. (triangle) and A. longifilis (circle).
diminishes its value as a diagnostic character.
Despite the diversity of the group, the occurrence of two
species of Akysis in close sympatry is only known from the
Endau River drainage, where A. microps and A. hendricksoni occur
syntopically in the Kahang River (Ng & Tan 1999), and
possibly in the Mekong River drainage (although known
distribution of the sympatric species are separated by greater
distances than is the case for A. longifilis and A. portellus sp. nov.;
see Ng & Sabaj 2005, Image 2). Given the close overall
similarity between A. longifilis and A. portellus, it is not surprising
that an unpublished phylogenetic analysis using nuclear and
mitochondrial markers revealed them to be sister taxa. The
evoluionary implications of this are still being investigated
and will be reported on at a later date.
COMPARATIVE
MATERIAL
Akysis brachybarbatus: CMK 5667 (2 paratypes), 33.234.1mm
SL; China: Yunnan, Menlian county.
A. fuliginatus: UMMZ 241338 (holotype), 21.5mm SL;
UMMZ 235691 (2 paratypes), 19.119.9mm SL; Cambodia:
Stung Treng province, Mekong River on W edge of Kaoh Han,
16km NE of Stung Treng, 13o38N-106o3E.
A. longifilis: UMMZ 246172 (holotype), 33.8mm SL; UMMZ
245966 (7 paratypes), 31.553.1mm SL; ZRC 51157 (14), 26.2
44.6mm SL; Myanmar: Bago division, Pyu township, Pyu
stream (tributary of Sittang River) ca. 229km from Yangon.
A. manipurensis: data from Vishwanath et al. (2007).
A. pictus: BMNH 1880.12.1.25-26 (2 syntypes), 37.742.4mm SL; Myanmar: Tenasserim. UMMZ 245965 (1),
59.2mm SL; Myanmar: Kayin state, hillstreams in Ataran River
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drainage in the vicinity of Payathonzu, 15o25N-98o15E.
A. prashadi: ZSI F10873/1 (holotype), 38.3mm SL;
Myanmar: Kachin state, Myitkyina district, S end of Lake
Indawgyi and along W shore near Lonton village. CAS 98615
(1), 62.1mm SL; Myanmar: Sagaing division, Kalemyo markets.
CAS 98616 (3), 20.850.4mm SL; Myanmar: Kachin state,
Ayeryawaddy River, just S of Myitkyina. NRM 41051 (1),
45.5mm SL; Myanmar: Kachin state, Nant Yen Khan Cheng,
effluent of Lake Indawgyi, upstream of road near Lonton
village. UMMZ 245488 (16), 35.744.6mm SL; Myanmar:
Kachin state, Myitkyina district, hillstreams at Tonpan village,
on road from Myitkyina to Tanai.
A. pulvinatus: UMMZ 248249 (holotype), 29.6mm SL; ZRC
51009 (3 paratypes), 21.726.6mm SL; Thailand; Ranong
province, stream draining into Andaman Sea upstream of
Kapoe, 9 o 3414.0N-98 o 4140.4E. UMMZ 245696 (1
paratype), 26.5mm SL; Thailand: Ranong province, Baan Na
district, hillstreams flowing from Langkatuek, Klong Naka.
UMMZ 248250 (2 paratypes), 22.823.9mm SL; Thailand;
Phang Nga province, Tapi River drainage, Khlong Sok at Khao
Sok canoe point, ca 5km upstream of fish cave, 8o5245.8N98 o 4119.4E.
A. variegatus: RMNH 6881 (16), 22.233.3mm SL; Java:
Batavia [=Jakarta] and Parongkalong [=Parungkarang].
ZMA 104.652 (1), 30.2mm SL; Java: Batavia [=Jakarta].
A varius: ZRC 41015 (holotype), 30.8mm SL; CMK 12609,
1 paratype, 23.0mm SL; Laos: Khammouan province, Xe
Bangfai about 3km upriver of Ban Pakphanang. CMK 12433
(6 paratypes), 13.521.7mm SL; Laos: Khammouan province,
Xe Bangfai, rapids about 2km upriver of Ban Pungxe. UMMZ
214913 (2 paratypes), 20.420.6mm SL; Thailand: Ubon
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A new catfish Akysis portellus from Myanmar
H.H. Ng
Ratchathani province, Khong Chiam district, Huay Kwang, 1.5
km upstream from Mun River. USNM 232390 (7 paratypes),
16.220.7mm SL; Thailand: Nakhon Ratchasima province, Lam
Nam Mun, about 1km below dam and 2 km downstream from
Phima.
A. vespa: ZRC 46423 (holotype), 30.0mm SL; CMK 17788
(8 paratypes), 15.731.4mm SL; CMK 17953 (5 paratypes),
16.720.9mm SL; CMK 17977 (5 paratypes); ZRC 49155 (4
paratypes), 16.428.9mm SL; Myanmar: Kayin state, stream
Chon Son between Kyondaw and Phadaw, about 20km NW
of Payathouzu (at border with Thailand), 15 o25N-98o15E.
A. vespertinus: UMMZ 248755 (holotype), 34.3mm SL;
UMMZ 248756 (4 paratypes), 26.933.6mm SL; UMMZ
248757 (2 paratypes), 23.224.6mm SL; CMK 20752 (2
paratypes), 26.029.5mm SL; ZRC 51435 (2 paratypes), 26.8
27.1mm SL; Myanmar: Rakhine state: headwaters of Ann
Chaung drainage, approx 19km E by S of Ann, 19 o 43N94 o 11E.
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Threatened Taxa | www.threatenedtaxa.org | January 2009 | 1(1): 02-08