Phuket mar. biol. Cent. Res. Bull. 80: 101–106 (2023)
DOI: 10.14456/pmbcrb.2023.7

FIRST THAI RECORD OF Dasyscopelus brachygnathos (Bleeker, 1856) (Myctophidae)
FROM OFF PHUKET, ANDAMAN SEA
Surapong Bangchongmanee1, Charatsee Aungtonya1, Asuka Sugiyama2, Kota Obata2,
Shunsuke Yamashita2 and Toshio Kawai2*
Phuket Marine Biological Center, Mueang Phuket District, Phuket 83000, Thailand
Faculty, Graduate School / School of Fisheries Sciences, Hokkaido University, Hakodate,
Hokkaido 041-8611, Japan*Corresponding author: toshio.kawai@fish.hokudai.ac.jp
12

ABSTRACT: The first reliable record of Dasyscopelus brachygnathos (Bleeker, 1856) distributed in the
Andaman Sea of the Indian Ocean is proved based on the three specimens (62.3–64.6 mm standard length)caught from R/V Dr. Fridtjof Nansen trawling cruise survey on 8th September 1980, off the coast of theAndaman Sea, Phuket, Thailand, 300–400 m depth. This species is different from other congeners by their
combination of the following characters: body depth 22–27% of standard length; eye diameter 40–50% ofhead length; gill rakers on first arch 7–9 + 18–21; dorsal margin on operculum smooth; body scales markedly
ctenoid; scales over anal organ (AO) photophores without elongate spines; postero-lateral organ (Pol)located before a vertical from origin of base of adipose fin; first supraanal organ (SAO1) situated slightly
anterior to fourth ventral organ (VO4); a line through SAO1 and second supraanal organ (SAO2) passing
variously through or between second ventral organ (VO2) and third ventral organ (VO3); AO 6–9 + 3–6 =10–13.
Keywords: lanternfishes, Myctophum, Scopelus, Dasyscopelus pristilepis, R/V Dr. Fridtjof Nansen

INTRODUCTION
The myctophid genus Dasyscopelus Günther,
1864 of which type species is Myctophum asperum
Richardson, 1845 had been synonymized under
Myctophum Rafinesque, 1810 by many studies(e.g., Bolin 1959; Krefft and Bekker 1973; Paxton1979). Recently, several studies showed that Myctophum
is a paraphyletic group based on molecular analyses(Poulsen et al. 2013; Davis et al. 2014; Denton2014). Martin et al. (2018) showed myctophid
interrelationships using molecular data. Based on
their results, they recognized Dasyscopelus as valid
genus consisting of 7 species, i.e., D. asper (Richardson,
1845), D. brachygnathos (Bleeker, 1856), D.
lychnobius (Bolin, 1856), D. obtusirostris (Tåning,1928), D. orientalis Gilbert, 1913, D. selenops(Tåning, 1928) and D. spinosus (Steindachner,
1867).
The research vessel Dr. Fridtjof Nansen operates
within the EAF-Nansen project of FAO, and carries
out fish resources and ecosystems surveys in themaritime waters of developing countries, particularly
in Africa. The surveys are facilitated by FAO andthe vessel flies a UN flag. On 8th September 1980,
three specimens of species which belongs to Myctophidae
were captured from the Andaman Sea, off Phuket,
Thailand in the surveys. We identify and describe
these specimens in the present study.

MATERIALS AND METHODSCounts and proportional measurements follow
Hubbs and Lagler (1958). Terminology of photophoresof myctophids follows Wisner (1976). Standard
and head lengths are abbreviated as SL and HL,
respectively. Measurements were made to the nearest
0.1 mm with digital calipers. Dorsal, anal and principal
caudal-fin rays, and vertebrae were counted from aradiograph. Specimens examined in this study aredeposited at Phuket Marine Biological Center,
Phuket, Thailand (PMBC) and Naturalis Biodiversity
Center, Leiden, the Netherlands (RMNH).

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Phuket mar. biol. Cent. Res. Bull.

RESULTS AND DISCUSSION
Dasyscopelus brachygnathos (Bleeker, 1856)
Fig. 1
Scopelus brachygnathos Bleeker, 1856: 65 (typelocality: Manado, Indonesia).
Dasyscopelus pristilepis Gilbert and Cramer, 1897:
412, fig. 1 in pl. 39 (type locality: Hawaii).
Myctophum (Dasyscopelus) asperum: Bleeker 1870–1875:
159 (in part).
Myctophum (Dasyscopelus) brachygnathum: Bleeker
1870–1875: fig. 3 in table 277.
Myctophum pristilepis: Weber and de Beaufort 1913:
165, fig. 64 (Macassar Straits; Halmahera Sea;
Banda Sea; Arafura Sea); Becker and Borodulina
1976: 132 (tropical area in the Indo-Pacific).
Myctophum (Myctophum) brachygnathos: FraserBrunner 1949: 1058 (only listed).
Myctophum brachygnathos: Sarenas 1954: 399, fig. 6(Philippines); Paxton 1979: 15 (Manado; Hawaii).
Myctophum pristilepis: Sarenas 1954: 402, fig. 7(Philippines).
Myctophum brachygnathum: Kawaguchi and Aioi
1972: 36 (key); Wisner 1976: 65, fig. 60(eastern Pacific); Gjøsæter 1977: 8 (Somalia
Peninsula); Becker 1983 (tropical area in the
Indo-Pacifc); Paxton and Hulley 2000: 594(South China Sea); Hutchins 2001: 20 (Western
Australia); Mundy 2005: 228 (Hawaii); Paxton
et al. 2006: 526 (Australia); Vipin et al. 2011:
8 (Somalia Peninsula); Fricke et al. 2014: 30(Papua New Guinea).
Dasyscopelus brachygnathum: Martin et al. 2018:
83 (only listed); Psomadakis et al. 2019: 230(Myanmar).
Diagnosis: Body depth 22–27% SL; eye diameter
40–50% HL; gill rakers on first arch 7–9 + 18–21;
dorsal margin on operculum smooth; body scales
markedly ctenoid; scales over anal organ (AO)
photophores without elongate spines; postero-lateralorgan (Pol) located before a vertical from origin ofbase of adipose fin; first supraanal organ (SAO1)
situated slightly anterior to fourth ventral organ(VO4); a line through SAO1 and second supraanalorgan (SAO2) passing variously through or between
second ventral organ (VO2) and third ventral organ(VO3); AO 6–9 + 3–6 = 10–13 (Bleeker 1870–1875;

Gilbert and Cramer 1897; Weber and de Beaufort
1913; Fraser-Brunner 1949; Sarenas 1954;
Kawaguchi and Aioi 1972; Wisner 1976).
Materials: PMBC 29929, 3 specimens, 62.3–64.6mm SL, Andaman Sea, 300–400 m depth, trawl,
R/V Dr. Fridtjof Nansen, 8 September 1980.
Description: Counts: dorsal-fin rays 13; anal-fin
rays 18; pectoral-fin rays 18; pelvic-fin rays 8; vertebrae
15 + 20 = 35; gill rakers on first arch 7 + 19 = 26;
dorsonasal organ (Dn) 0, ventronasal organ (Vn) 0,
suborbital organ (So) 0, supraorbital organ (Suo) 0,
branchiostegal organ (Br) 3, opercular organ (Op) 2,
pectorolateral organ (PLO) 1, pectoroventral organ(PVO) 2, ventrolateral organ (VLO) 1, thoracic organ(PO) 5, VO 4, SAO 3, AO 7 + 4 = 11, Pol 1, precaudalorgan (Prc) 2. Proportions as % of SL; head length
28.3–29.2; depth of head 21.8–23.2; body depth
23.2–23.7; snout length 3.3–4.0; eye diameter
11.8–11.9; length of orbit 12.1–12.5; interorbital
width 7.9–8.6; length of upper jaw 17.0–18.3;
depth of caudal peduncle 8.0–8.9; length of caudal
peduncle 17.1–18.6; length of dorsal-fin base 11.7–
13.6; height of dorsal fin 14.0–15.7; length of analfin base 23.7–24.1; height of anal fin 10.7–16.4;
length of pectoral fin 16.4–19.3; length of pelvic
fin 9.2–11.7; predorsal length 44.1–48.0.
Body slender, compressed and cylindrical. Snout
short. Eye relatively large, eye diameter 2.38–2.47
in HL. Mouth large, upper jaw length 1.57–1.67 in
HL. Teeth on jaws very small. Gill rakers slender
and well developed. Dorsal margin on operculum
smooth. Lateral line well developed. Caudal peduncle
shorter than anal-fin base. Anus below mid of
dorsal-fin base. Anal-fin origin posterior to posterior
end of dorsal-fin base, posterior end of anal-finbase posterior to adipose fin. Dorsal-fin base shorter
than anal-fin base. Scales markedly ctenoid; scales
over AO photophores without elongate spines.
Op consisting 2 photophores, Op1 situated at
level of just below ventral margin of eye, Op2behind of posterior margin of upper jaw. PLO closer
lateral line than pectoral-fin base. PVO1 situatedon the straight line connecting between PO1 andPVO2. PO consisting 5 photophores along withventral margin of body. VLO situated on middle
between lateral line and pelvic-fin base. VO consisting
4 photophores, all along with ventral margin of

103First Thai record of Dasyscopelus brachygnathos (Bleeker, 1856)
body. Straight line passing SAO1 and SAO2 passing
between VO2 and VO3. SAO1 situated slightly
anterior to VO4. SAO3 just below the lateral line.
Space present between anterior anal organ (AOa)
and posterior anal organ (AOp) which are alongwith ventral margin of body. Single Pol situatedanterior to adipose fin and below lateral line. Prc
including 2 photophores far from lateral line.
Supracaudal gland (SUGL) absent, infracaudal
gland (INGL) present.
Color after fixation. Body and all fins uniformly
light brown except for dusky dorsal margin of bodyand base of caudal fin. Photophores light brownsurrounded by black edge. INGL milky white.
Comparative materials: RMNH.PISC 6932,
syntypes of Scopelus brachygnathos Bleeker, 1856,
2 specimens, 41.7, 53.0 mm SL.
Distribution: Tropical area between about latitude
10 degrees north and 10 degrees south in the Indian
Ocean, and tropical area between about latitude 30
degrees north and 20 degrees south in the Pacificeast to longitude 130 degrees west (see details inthe synonym list of the species).
Identification: The present specimens are different
from D. lychnobius, D. obtusirostris and D. spinosus
by smooth on dorsal margin of operculum (vs. serrate
in the 3 species: Wisner 1976; Fujii 1988; Nakabo
and Kai 2013; Robertson and Clements 2015).
Also, the specimens differ from D. lychnobius and D.
spinosus by scales over AO photophores without
elongate spines (vs. with 1–4 elongate spines:
Kawaguchi and Aioi 1972; Wisner 1976; Fujii
1988; Robertson and Clements 2015) and from D.
obtusirostris by markedly ctenoid scales on body(vs. cycloid or weak ctenoid: Kawaguchi and Aioi
1972; Fujii 1988; Nakabo and Kai 2013). The
specimens are distinguished from D. selenops inhaving SAO1 situated slightly anterior to VO4,and slender body, depth 23.2–23.7% SL (vs. SAO1
situated slightly posterior to VO4, and slightly
deep body, depth than 29%: Fraser-Brunner 1949;
Kawaguchi and Aioi 1972; Wisner 1976; Nakabo
and Kai 2013; Robertson and Clements 2015). The

specimens differ from D. asper and D. orientalis by 7
+ 19 gill rakers (vs. 4 + 10–14 in the former species,and 5–6 + 13–16 in the latter: Kawaguchi and
Aioi 1972; Wisner 1976; Fujii 1988; Robertson andClements 2015). In addition, the specimens are
separable from D. asper by a line through SAO1
and SAO2 passing between VO2 and VO3 (vs.
a line through SAO1 and SAO2 passing variously
between VO1 and VO2, or before VO1: Kawaguchi
and Aioi 1972; Wisner 1976; Robertson andClements 2015), and from D. orientalis by larger
eye, diameter 40.5–42.1% HL (vs. ca. 36%: Gilbert
1913; Fraser-Brunner 1949). On the other hand,the specimens well agree with D. brachygnathos
by diagnostic characters mentioned above (seeDiagnosis). Therefore, we identified the specimens
as D. brachygnathos.
Remarks: In the Indian Ocean, this species had
been known from tropical area between about latitude
10 degrees north and 10 degrees south (Becker and
Borodulina 1976), off Somalia Peninsula (Gjøsæter
1977; Vipin et al. 2011), off northwestern Australia(Paxton et al. 2006) and off Myanmar (Psomadakis
et al. 2019). Becker and Borodulina (1976) showeda distributional map of Myctophum pristilepis
which is now recognized as a junior synonym ofDasyscopelus brachygnathos (e.g., Fraser-Brunner
1949; Becker 1983). Although they indicated that
this species collected at Nicobar Islands (seefig. 4 in Becker and Borodulina 1976), they did
not show their detail localities whether inside ofAndaman Sea or not. Although Psomadakis et al.
(2019) listed this species from off Myanmar, theyalso did not indicate its detail localities whether
this species was captured from Bay of Bengal or
Andaman Sea. Therefore, this report is the firstreliable record of Dasyscopelus brachygnathos
from Andaman Sea. In addition, this is the firstrecord of the species from Thai waters because thisspecies had never been known (e.g., Pokapunt etal. 1983; Monkolprasit et al. 1997; Satapoomin
2011).
New Thai name of this species is “Pla-Ta-KiangPak-Sun” named after “short-jawed lanternfish”
which is English common name of the species.

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Phuket mar. biol. Cent. Res. Bull.

Figure 1. Dasyscopelus brachygnathos, PMBC 29929, 64.6 mm SL.

ACKNOWLEDGEMENTS
We sincerely thank S. Panjarat (Fisheries Development Policy and Planning Division,
Department of Fisheries, Thailand) and staff of theReference Collection of PMBC for their help of ourresearch in PMBC. We are grateful to H. Imamura
and F. Tashiro (Hokkaido University, Japan) for

their fruitful feedback and comments to an earlydraft of this manuscript. We also thank to E. Dondorp(RMNH) for accessing comparative materials. This
study was partially supported by JSPS KAKENHI
Grant Numbers JP20K01118 and JP23K05364,
and JST SPRING Grant Number JPMJSP2119.
We appreciated the comments and suggestions fromanonymous referees for improving the manuscript.

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Manuscript received: 27 June 2023
Accepted: 9 August 2023