First record of Macrognathus aral (Bloch & Schneider, 1801) from the Himalayan Kingdom of Bhutan

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RESEARCH ARTICLE
Fish Aquat Sci. 2023;26(12):708-714
https://doi.org/10.47853/FAS.2023.e63
eISSN 2234-1757
Introduction
Bhutan is located in the southern slopes of eastern Himalayas
(Caspari et al., 2006) and is a part of 36 global biodiversity
hotspots (Myers et al., 2000). The wide spectrum of ecological
conditions ranging from subtropics to alpine meadows has
endued the country with rich biological diversity including shes
(Gurung & oni, 2015). e country is home to 125 sh species
(NBC, 2019) under eight orders (Anguilliformes, Beloniformes,
Cypriniformes, Perciformes, Salmoniformes, Siluriformes,
Synbranchiformes, and Tertadontiformes) and 24 families
(Gurung & oni, 2015). Majority of the species belong to orders
Cypriniformes and Siluriformes holding high significance in
economic landscape, aquaculture, and source of animal protein
(Gurung & Thoni, 2015; Nikam et al., 2014; Thai et al., 2007).
However, species under other orders and families including
Matsacembelidae contribute equally to the economic as well as
social livelihood in the country.
Family Mastacembelidae under order Synbranchiformes
contains spiny eels with elongated body, having 7–40 depressible
well-separated dorsal spines, one to three anal spines, body
covered with small scales, lack of pelvic fins and girdles, gill
Received: Mar 29, 2023 Revised: Sep 5, 2023 Accepted: Sep 6, 2023
*Corresponding author: Laxmi Sagar
College of Natural Resources, Royal University of Bhutan, Lobesa, Punakha 14001, Bhutan
Tel: +975-17-924508, E-mail: sagarlssagar19@gmail.com
is is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-
nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
Copyright © 2023 e Korean Society of Fisheries and Aquatic Science
First record of Macrognathus aral (Bloch & Schneider,
1801) from the Himalayan Kingdom of Bhutan
Laxmi Sagar1, *, Karma Lodhen Wangmo1, Dhan Bdr. Gurung2, Karma Wangchuk3, Rinchen Dorji1,
Rupesh Subedi1, Tshering Zangmo1, Pelden Dorji1
1
College of Natural Resources, Royal University of Bhutan, Lobesa, Punakha 14001, Bhutan
2
Professor, Department of Forest Science, College of Natural Resources, Royal University of Bhutan, Lobesa, Punakha 14001, Bhutan
3
Lecturer, Department of Food Science and Technology, College of Natural Resources, Royal University of Bhutan, Lobesa, Punakha 14001, Bhutan
Abstract
This study reports a new record of freshwater sh Macrognathus aral (Bloch & Schneider) from Aiechu-Kalikhola tributary of the
Maukhola river in Sarpang, Bhutan. The species was found in shoal of the tributary and was identied using its morphometric
characters. It can be identied and distinguished from its congeners reported in Bhutan by dorsal n rays XIX, 47, anal n rays
III, 52, rostral plates 28, pectoral n rays 19, caudal n rays 15, soft rayed part of dorsal and anal n separated by a notch from
rounded caudal n, and presence of four ocelli at the base of dorsal ns. Further studies are needed to better understand its dis-
tribution, ecology, and population dynamics in the country. A key to species belonging to Mastacembelidae of Bhutan including
the new record is provided.
Keywords: Aiechu-Kalikhola, Bhutan, Congeners, Macrognathus aral, New record

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openings on later sides of head, short caudal fin with laterally
compressed body towards the caudal region (Arunkumar, 2020;
Plamoottil & Abraham, 2014). Globally, Mastacembelelidae
consist of three genera (Mastacembelus Scolopi 1777,
Macrognathus Lacepède, 1800, Sinobdella Kottelat & Lim, 1994)
distributed in Africa, the Middle East, Southeast Asia, China,
Vietnam, and Laos (Nelson et al., 2016; Yuan et al., 2020). Gurung
et al. (2013) recognized two genera of spiny eels (Macrognathus
and Mastacemblus) from Bhutan.
Based on current records only three species of spiny eels,
namely Macrognathus morehensis Arunkumar & Singh, 2000,
Macrognathus pancalus Hamilton, 1822, and Mastacembelus
armatus Lacepède, 1800 are found in inland aquatic habitats
of Bhutan (Gurung & Thoni, 2015; NRDCR & LF, 2020).
Arunkumar (2016, 2020) recognized the presence of other species
of Macrognathus including Macrognathus aral Schneider and
Bloach 1801 from transboundary river drainages of Bhutan.
However, M. aral has not been reported from Bhutan, but the
authors have recorded a single specimen from Aiechu-kalikhola
tributary of Maukhola river at Gelephu town under Sarpang
district. Apart from the description of the new record, the authors
have also developed a comprehensive key to identify species under
Mastacembelidae of Bhutan by examining specimens present in
the Ichthyology Laboratory, College of Natural Resources (CNR),
Royal University of Bhutan (RUB) and comparing pertinent
literature (Jayaram, 2010).
Materials and Methods
Specimen collection and preservation
A single specimen of M. aral was collected using Electro shocker
(Honda GCV 160cc, Honda, Tokyo, Japan) from 26°53.314’ N,
90°31.187’ E on 16 October, 2022. General water parameters
were recorded on site using HACH kit (HQ40d, Hach, Loveland,
CO, USA) and riparian vegetation was noted. Additionally, other
species associated with M. aral in the tributary was also examined.
Following Arunkumar (2020) the color of the specimen was
noted while it was fresh and euthanized using 0.2 mL of clove oil
per 500 mL of water and treated with 10% formalin (Fernandes et
al., 2017). e xed specimen was preserved in 70% ethyl alcohol
and catalogued at the Ichthyology Laboratory, CNR, RUB (RUB/
CNR/Fish sample/Aiechu-kalikhola/16.10.2022/223).
Species identication and measurement
Identication of the species by comparing it with existing species
from Bhutan and adjacent areas was carried out following
; Arunkumar (2020); Biswas et al. (2007); Gurung & Thoni
(2015); Jayaram (2010) ; NRDCR & LF (2020); Shrestha (2008);
Vishwanath et al. (2007). Methods followed are those of Jayaram
(2010). All the measurements were made with digital caliper to
nearest 0.1 mm and expressed as percentage of standard length
(SL) (Arunkumar, 2020; Duong et al., 2020). Additionally, for
diagnostic, spines and fin rays were counted using microscope
(Nikon SMZ445, Nikon, Tokyo, Japan). Standard practices of
Jayaram (2010); Ng & Tan (2020); Roberts (1980, 1986) were
referred.
Results
Scientic history
The initial documentation of a spiny eel, identified as
Rhynchobdella aral, originated from Tranquebar, Tamil Nadu,
India (Talwar & Jhingran 1991). The species under genera
Macroganthus found in the Indian subcontinent has been
consistently referred to as M. aculeatus by nearly all authors
(Roberts, 1980). However, there are no type specimens for M.
aral (Roberts, 1980). Rhynchobdella ocellata was described from
Pondicherry, India which was later considered as secondary
junior homonym of M. ocellatus (Kottelat, 2013). Subsequently, a
new species of spiny eel (R. ocillata) was described from Tenasseri,
Myanmar but was considered incorrect subsequent spelling of
M. ocellatus (Kottelat, 2013). Hora (1921) reported a new species
of Mastacemblid (R. dhanashorii) from Manipur, India, with the
only known holotype which was later declared as an ambiguous
synonym of M. aral. Malhotra & Dutta (1975) reported a new
species of spiny eel (M. jammuensis) from Jammu, India but was
declared as a synonym of M. aral (Talwar & Jhingran, 1991).
e current status of the species is valid as M. aral (Arunkumar,
2020).
Diagnostic character
Body elongated eel like, presence of paired tooth plates along the
concave ventral surface of rostrum, snout trilobed, rim of anterior
nostril with six nger like mbriae, gape of mouth narrow, jaws
with small pointed teeth, pre-orbital and pre-opercular spines
absent or smooth, a distinct band on either side of the body
above lateral line which becomes obscure in the post-anal region,
presence of depressible dorsal spines, anal n with three spines,
caudal n rounded, the dorsal n originate much posterior to the
pictorial n, so dorsal and so anal n partially separated by a

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notch from rounded caudal n, presence of four ocelli at dorsal
fin base, ocellus at base of caudal fin absent. Body count and
measurements are shown in Tables 1 and 2 respectively.
Fin formula: D. XIX, 47; P. 19; A. III, 52; C. 15 (23.71 cm TL,
22.13 cm SL)
Coloring pattern
Body brownish or greenish, yellowish along the abdomen which
becomes lighter below, black shades of caudal, so dorsal and so
anal ns (Fig. 1).
Distribution in Bhutan
Currently known to occur only in Aiechu-Kalikhola tributary of
Maukhola river under Sarpang district.
Water parameters and habitat type of Aiechu-Kalikhola trib-
utary
Seven water parameters (Table 3) were recorded from the point
where the specimen was found. Water temperature (℃), dissolved
oxygen (DO) (mg/L), conductivity (S/m), total dissolved solids
(mg/L), pH, and salinity (g/kg) were recorded onsite while
ammonia (µmol/L) was tested at the Soil Water and Air Testing
(SWAT) laboratory, CNR, RUB. e habitat was predominantly
subtropical with following floras; Senegalia catechu, Ficus
semicordata, Toona ciliate, Bombax ceiba, Ficus racemose, Murraya
paniculate, Lantana camara, Urena lobata, Solanum viarum,
Chromolaena odorata, Sida acuta, Oxalis corniculate, Borreria
latifolia, Piper sp., Synedrella nodiora, and Cyanotis vaga.
Associated species
A total of 21 species un
der 10 families (Table 4) were recorded in
the Aiechu-Kalikhola tributary where M. aral was found. e most
abundant species was Copper mahseer (Neolissochilus hexagonolepis
McClelland, 1839) (N = 12), followed by Hamilton’s barila (Opsarius
bendelisis Hamilton, 1807) (N = 8) and Giant Daino (Devario
aequipinnatus McClelland, 1839) (N = 7) while Glyptothorax botius
(Hamilton, 1822) and Golden mahseer (Tor putitora, Hamilton
1822) were the least abundant species (N = 1 each).
Discussion
Distribution
The native range of M. aral includes lowland habitats of Indian
subcontinent including, Bangladesh, Pakistan, Sri Lanka,
Table 1. Meristic characters of the new record (Macrognathus aral) compared with reference data and spiny eels reported
from Bhutan


M. aral Macrognathus pancalus Macrognathus morehensis Mastacembelus armatus
Present study Jayaram (2010) Gurung & Thoni (2015) NRDCR & LF (2020) Gurung & Thoni (2015)
Dorsal n rays XIX, 47 XVI–XXIII, 47–48 XXIV–XXVI, 30–42 XI–XVI, 39–51 XXXIII–XXXX, 67–82
Anal n rays III, 52 II–III, 44–52 III, 31–46 III, 40–54 III, 67–83
Pectoral n rays 19 19 17–19 15–20 23
Caudal n rays 15 15 11–13 11–14 14–17
Rostral plates 28 14–28 Absent 8–11 Devoid
Table 2. Morphometric measurements of Macrognathus aral
recorded in the present study and compared with reference
data
Present study
(cm) % of SL Das et al. (2023)
(cm)
Total length 23.7 15.7–32.5
Standard length 22.1 14.7–27.2
Head length 3.6 16.5 2.5–4.5
Pre-pectoral length 4.1 18.5 2.7–5.0
Pre-dorsal length 7.5 34.0 5.9–11.0
Pre-anal length 12.9 58.6 9.7–17.9
Base of pectoral length 0.5 2.5 0.3–0.6
Base of dorsal length 8.0 36.2 8.4–15.6
Base of anal length 7.9 36.0 4.8–8.9
Pectoral n length 1.3 6.2 0.9–1.6
Dorsal n length 0.9 4.2 0.5–1.0
Anal n length 0.6 2.8 0.4–0.7
Caudal n length 1.6 5.2 1.0–1.8
Body depth 2.6 11.7 1.7–3.5
Pre-orbital length 1.9 5.3 1.1–2.0
Post-orbital length 2.1 9.6 1.2–2.2
Eye diameter 0.3 1.3 0.2–0.3
SL, standard length.

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Nepal, and Myanmar (Talwar & Jhingran, 1991). In the Indian
subcontinent M. aral is uniformly distributed where it holds high
significance as food and ornamental fish and is widely used in
aquarium trade due to its slender body, attractive color pattern,
and playful nature (Abujam et al., 2013; Gupta, 2016). Studies
have recognized the presence of M. aral from Northeast India
including Assam (Arunkumar, 2016; Dhanze et al., 2018; Gupta,
2016) which shares a close boarder with the current study area
making the presence of M. aral highly probable. e preliminary
checklist of shes of Bhutan (Gurung & oni, 2015) and shes
of Eastern Bhutan (NRDCR & LF, 2020) have reported M.
pancalus and M. morehensis respectively, from the same tributary
(Aiechu-Kalikhola). However, there was no confirmation of M.
aral from Aiechu-Kalilhola. is study conrms the presence and
distribution of M. aral in Aiechu-Kalikhola tributary of Maukhola
river in Sarpang district. Additionally, pertinent published
literatures have reported the co-occurrence of M. aral and M.
pancalus in single river system and basins (Arunkumar, 2020;
Talwar & Jhingran, 1991).
Macrognathus aral diers from M. pancalus in a number of
features. e most distinguishable taxonomic feature includes the
presence of rostral tooth plates in M. aral (Fig. 2) which are absent
in M. pancalus (Arunkumar & Singh, 2000), lesser dorsal spines
(16–23 vs. 24–26), more soft dorsal fin rays (47–48 vs. 30–42)
(Jayaram, 2010), preopercular and pre-orbital spines (absent vs.
present) (Talwar & Jhingran, 1991). Similarly, M. aral diers from
M. morehensis in many significant taxonomic characters. Data
Fig. 1. Macrognathus aral (Bloch & Schneider, 1801), 22.13 cm SL, caught by electro shocker, 16 October 2022, Aiechu-
Kalikhola, Sarpang, Bhutan.
Table 3. Water parameters from the point where new record
of Macrognathus aral was found
nHighest Lowest Mean SD
Ammonia (µmol/L) 40.0 0.0 0.0 0.0
Conductivity (S/m) 4226 170 187.5 12.9
DO (mg/L) 48.5 7.3 8.1 0.5
pH 48.1 7.4 7.7 0.1
Salinity (g/kg) 40.1 0.08 0.09 0.007
TDS (mg/L) 4105.5 78.1 86.8 6.3
Temperature (℃) 4 28.5 25.7 26.7 1.2
n, number of samples; DO, dissolved oxygen; TDS, total dissolved solids.
Table 4. Associated species with Macrognathus aral in Aiechu-
Kalikhola tributary
Species Family NIUCN status
Badis badis Nandidae 3Least concern
Balitora brucei Balitoridae 2Near threatened
Batasio batasio Bagridae 2Least concern
Cyprinion semiplotum Cyprinidae 4Vulnerable
Danio dangila Danionidae 4Least concern
Danio rerio Danionidae 2Least concern
Devario aequipinnatus Danionidae 7Least concern
Esomus danrica Danionidae 4Least concern
Garra arupi Cyprinidae 4Data decient
Garra birostris Cyprinidae 3Data decient
Glyptothorax botius Sisoridae 1Least concern
Lepidocephalichthys guntea Cobitidae 2Least concern
Neolissochilus hexagonolepis Cyprinidae 12 Near threatened
Opsarius barna Cyprinidae 5Least concern
Opsarius bendelisis Cyprinidae 8Least concern
Paracanthocobitis botia Nemacheilidae 3Least concern
Pethia conchonius Cyprinidae 6Least concern
Psilorhynchus homaloptera Psilorhynchidae 2Least concern
Schistura savona Nemacheilidae 2Least concern
Tor putitora Cyprinidae 1Endangered
Xenentodon cancila Belonidae 2Least concern
IUCN, international union for conservation of nature.

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of Arunkumar & Singh (2000) for M. morehensis were used for
comparison. It can be easily distinguished from M. morehensis
by presence of more rostral plates (14–28 vs. 8–11), more dorsal
spines (16–23 vs. 11–16), more caudal fin rays (15 vs. 11–14),
pattern of band (longitudinal stripes along entire length vs. 20–25
transverse dark band), and ocellus at the base of caudal n (absent
vs. present).
Identication key to Mastacembelidae of Bhutan
Key to genera
Dorsal fin spines less than 33 (11–26), snout trilobed,
ventral surface of rostrum with tooth plates. Rim of
anterior tubular nostril with six finger-like projection (Fig.
3A)………………………………………………Macrognathus
Dorsal fin spines 33 or more, no tooth plats in rostrum. Rim
of anterior tubular nostrils with two broad-based flaps (Fig.
3B)…..………………………………………….Mastacembelus
Key to species of Genus Macrognathus
1. Concave ventral surface of rostrum with paired tooth
plates………………….………………………………………2
Rostrum globous, without tooth plates………………………3
2. Rostral tooth plates 8–11, Dorsal n spines 11–16……………
…………………………….……………………M. morehensis
Rostral tooth plates 14–28, Dorsal n spines 19–23……………
……….…………………………………………………M. aral
3. Caudal n with 11–13 rays...…………………………………4
4. Dorsal n spines 24–26 and 30–42 so rays………M. pancalus
Key to species of Genus Mastacembelus
1. Caudal 
n homocercal, conuent with the dorsal and anal ns.
Caudal n rays 14–16…………………….…………
M. armatus
Competing interests
No potential conict of interest relevant to this article was re-
ported.
Fig. 2. Dorsal and ventral visualizations of rostrum in
Macrognathus aral. Adapted from Jayaram (2010) with
permission of Narendra Publishing House.
Fig. 3. Distinctive nasal structure in Macrognathus and
Matacembelus. (A) Rim of anterior nostril with six finger-
like projection in Macrognathus; (B) two broad-based flaps in
Mastacembelus. Adapted from Jayaram (2010) with permission
of Narendra Publishing House.

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Funding sources
Not applicable.
Acknowledgements
e authors would like to thank Department of Forest and Park
Services for granting clearance to collect samples and conduct
the study. We would like to thank senior lab in-charges Mr. So-
nam Moktan and Mr. Ugyen Tenzin for their assistance during
specimen identification. We remain grateful to Mr. Kinga as
well, sherman Gelephu, Sarpang, Bhutan for all the technical
and logistic support.
Availability of data and materials
Upon reasonable request, the datasets of this study can be avail-
able from the corresponding author.
Ethics approval and consent to participate
is study conformed to the guidance of animal ethical treat-
ment for the care and use of experimental animals.
ORCID
Laxmi Sagar https://orcid.org/0000-0002-9788-6770
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