H. Motomura and K. Matsuura (eds) Fishes of Yaku-shima Island
National Museum of Nature and Science, Tokyo, 10 March 2010

First records of a triplefin (Tripterygiidae),
Enneapterygius hemimelas, from Japan
Masatoshi Meguro* and Hiroyuki Motomura
Kagoshima University Museum, 1-21-30 Korimoto, Kagoshima 890-0065, Japan*
Corresponding author: e-mail: fisheries_kago_mm7190@hotmail.co.jp

Abstract Four male specimens (19.4–21.8 mm standard length) of Enneapterygius hemimelas (Knerand Steindachner, 1867) (Tripterygiidae) were collected from Yaku-shima Island, Kagoshima Prefecture, Kyushu, Japan. Because previous Japanese records of E. hemimelas were based on mis-identifications of E. bahasa or E. flavoccipitis, and the northernmost record of E. hemimelas was Taiwan,
the Yaku-shima Island specimens examined in this study represent the first records of E. hemimelasfrom Japan and the northernmost record for the species.
Key words: Tripterygiidae, Enneapterygius hemimelas, distribution, Yaku-shima Island, Japan.

Introduction
The triplefin genus Enneapterygius Rüppell,1835 (Perciformes: Tripterygiidae) in the western and central Pacific Ocean was reviewed by
Fricke (1997), then Fricke (2009) recognized 42
valid species in the region. In addition, E. sheni
and E. shaoi were described by Chiang and Chen
(2008) as new species from Taiwan. Three species
originally described by Shen (1994), E. erythrosomus, E. hsiojenae, and E. leucopunctatus, weresynonymized by Fricke (1997) with E. rubicauda
Shen, 1994, E. vexillarius Fowler, 1946, and E.
vexillarius respectively. However, Chiang andChen (2008) redescribed E. erythrosomus, E.
hsijenae, and E. leucopunctatus as valid species.
Furthermore, although Fricke (1997) regarded E.
rubicauda as a valid species, Chiang and Chen
(2008) considered it a junior synonym of E. flavoccipitis Shen, 1994. Thus, a total of 46 species
has currently been recognized as valid membersof Enneapterygius in the western and central Pacific Ocean.
Enneapterygius, the most speciose genus
among the Tripterygiidae, has been defined by adiscontinuous lateral line with an anterior series of
6–22 pored scales and a posterior series of 13–27
notched scales, a first dorsal fin with 3 spines,

an anal fin with 1 spine, a pelvic fin with 1 spineand 2 soft rays, and the head, opercle, pectoral-finbase and abdomen naked (Fricke, 1997). However, synapomorphies for the genus have not been
defined, and further investigation at the genericlevel is therefore necessary (Motomura et al.,2005).
Enneapterygius hemimelas was originallydescribed by Kner and Steindachner (1867) as
Tripterygium hemimelas from the Samoa Islands,
and Fricke (1994) designated a male specimen(USNM 220068, 20.6 mm SL, Fagasa Bay, Tutuila Island, American Samoa) as the neotype forthe species. Enneapterygius hemimelas is currently known from Taiwan, the Philippines, andIndonesia east to Samoa (Fricke, 2009). Previous
Japanese records of E. hemimelas were, in fact,
mis-identifications of E. bahasa Fricke, 1997 or E.
flavoccipitis (see Remarks).
During ichthyofaunal surveys of Yaku-shimaIsland, Kagoshima Prefecture, Kyushu, Japan(Motomura et al., 2010), four male specimens ofE. hemimelas were collected from the southerncoast of the island. These specimens are describedherein as the first records of E. hemimelas fromJapan and the northernmost record for the species.

1M. Meguro and H. Motomura

Fig. 1. Enneapterygius hemimelas from Yaku-shima Island, Kagoshima Prefecture, Japan (KAUM–I. 11353, male, 19.5 mm
SL). A and B indicate fresh and preserved specimens respectively.

Materials and methods
Counts and measurements follow Hubbs andLagler (1947), Fricke (1994, 1997) and Motomura
et al. (2005), with the mandibular-pore formula
following Fricke (1997). Measurements weremade to the nearest 0.1 mm with needle-point
calipers under a dissecting microscope. Standard
length is abbreviated as SL. Specimens of E.
hemimelas examined in this study are deposited at
the Kagoshima University Museum, Kagoshima,
Japan (KAUM) and the Museum Support Center, Smithsonian Institution National Museum of
Natural History, Suitland, USA (USNM).
Enneapterygius hemimelas (Kner and Steindachner, 1867)[English name: Halfblack Triplefin][New Japanese name: Akegoromo-hebigimpo](Figs. 1–3; Table 1)

2

Tripterygium hemimelas Kner and Steindachner,
1867: 371 (type locality: Fagasa Bay, Tutuila
Island, American Samoa, based on neotype).
Material examined. All specimens from
Yaku-shima Island, Kagoshima, Japan: KAUM–
I. 11353, male, 19.5 mm SL, east of Kamazenohana, Kurio, 30°16′03″N, 130°24′47″E, 0–3 m
depth, hand net, coll. by KAUM fish team, 12Aug. 2009; KAUM–I. 11354, male, 19.4 mm
SL, same data as KAUM–I. 11353; KAUM–I.
11355, male, 21.5 mm SL, same data as KAUM–
I. 11353; KAUM–I. 21659, male, 21.8 mm,
south of Kamazeno-hana, Kurio, 30°15′57″N,
130°24′57″E, 0–2 m depth, hand net, coll. by G.
Ogihara et al., 27 July 2009.

Enneapterygius hemimelas from Japan

Diagnosis. A species of Enneapterygius withthe following combination of characters: 12–14
second dorsal-fin spines; 15–18 + 17–19 lateralline scales; 35 or 36 longitudinal scales rows; 1
symphyseal mandibular pore; mandibular pores
usually 4 + 1 + 4 (rarely 6 + 1 + 5); blackish area
on lower head of mature males separated into
two parts, one extending from end of maxilla andnear posteroventral margin of orbit onto middle
and lower opercular margin and pectoral-fin base,and the other a narrow band, extending fromfront of upper lip to anteroventral margin of orbit;
in mature males, two broad, black bands below
third dorsal-fin base and caudal peduncle, the twobands joined ventrally; posterior half of anal fin
black in mature males; caudal fin semitransparent
white or yellow; caudal-fin base white; pectoraland pelvic fins and body (except for black areas)orange in mature males.

Fig. 2. Schematic depiction of melanistic male colorationof Enneapterygius hemimelas, based on three
specimens (KAUM–I. 11353, KAUM–I. 11354, and
KAUM–I. 21659) from Yaku-shima Island, Kagoshima
Prefecture, Japan. Dotted areas indicate melanistic
areas.

Description. Counts and measurements are
given in Table 1. Cephalic sensory pore systems
are illustrated in Figure 3. Body moderately elongate, slightly compressed anteriorly, progressively
more compressed posteriorly; dorsal profile ofsnout moderately steep; anterior nostril a short

Table 1. Counts and measurements, expressed as percentages of standard length, of Enneapterygius hemimelas, including
neotype, and non-types from Yaku-shima Island and the western Pacific.
This study
Fricke (1997)
Yaku-shima Island,
Tutuila Island,Western PacificJapan
American Samoa(neotype and non(non-types)(neotype)
types)
Males
Male
Males Females
n=4
n=1
n = 821
Standard length (mm)19.4–21.8
21.3
6.0–40.0
CountsSecond and third dorsal-fin rays
XII–XIV + 9–10
XII + 9XI–XIV + 6–10
Pectoral-fin raysii–iii + 5–6 + vi–viii
iii + 5 + vii
i–iv + 4–8 + vi–viii
Anal-fin rays
I, 18–19
I, 18
I, 15–20
Longitudinal scales rows
35-36
35
32–37
2
13–20
Pored lateral-line scales
16–18
15–16
2
16–22
Notched lateral-line scales
18–19
17–18
3
Mandibular pore formula
4+1+4 or 6+1+5
4+1+4
3–4+1–2+3–4
Measurements
Body depth
19.5–20.3 (19.9)
19.6
17.8–24.4
Body width
18.5–19.3 (18.6)
17.5
11.9–17.2
Head length
26.4–27.6 (26.9)
26.4
24.0–30.2
Snout length
8.6–9.2 (8.9)
8.9
4.8–6.1
5.7–7.1
Orbit diameter
9.9–11.0 (10.4)
10.0
8.2–12.7
Interorbital width
2.4–3.0 (2.8)
2.9
2.4–4.2
Upper-jaw length
10.9–12.0 (11.4)
11.9
9.1–12.0
Postorbital length
11.6–13.6 (12.5)
12.3—
Pre 1st dorsal-fin length
26.8–28.0 (27.2)
26.5
23.8–27.6
Pre 2nd dorsal-fin length
37.1–39.6 (37.9)
36.9
32.2–38.6
Pre 3rd dorsal-fin length
71.8–73.6 (72.3)
70.2
63.7–71.8
Preanal-fin length
48.8–51.4 (49.3)
47.2
47.3–55.3
Prepectoral-fin length
31.1–32.2 (31.4)
30.9
28.0–34.9
Prepelvic-fin length
21.9–23.0 (22.2)
21.5
20.9–25.6
Caudal-peduncle length
9.2–11.6 (10.5)
10.5
10.1–15.3
Caudal-peduncle depth
7.7–8.6 (8.0)
7.2
6.5–9.7
1st spine length of 1st dorsal fin
10.4–11.0 (10.6)
10.0
7.7–12.4
5.8–7.9
2nd spine length of 1st dorsal fin
9.3–10.2 (9.6)
9.1
6.7–11.6
8.3–9.4
3rd spine length of 1st dorsal fin
7.2–8.8 (8.0)
7.8
4.5–9.7
Longest spine length of 2nd dorsal fin
13.1–14.4 (13.9)
13.6—
Longest ray length of 3rd dorsal fin
15.3–15.7 (15.5)
15.4
13.7–20.2
Pectoral-fin length
30.3–32.8 (31.7)
31.5
27.5–36.3
2nd ray length of pelvic fin
21.1–24.0 (23.3)
24.9
20.2–25.2
1Counts were based on 82 specimens, but the number of specimens measured was not indicated by Fricke (1997). 2Counts
included scales on right and left sides of the neotype. 3Only one specimen had 6 + 1 + 5. Means in parentheses.

3M. Meguro and H. Motomura

Fig. 3. Cephalic sensory pore systems of Enneapterygius hemimelas (KAUM–I. 11353, male, 19.5 mm SL, Yaku-shimaIsland, Kagoshima Prefecture, Japan). (A) Dorsal, (B) lateral, and (C) ventral views of head. Bar represents 1 mm.

4

Enneapterygius hemimelas from Japan

membranous tube with an unbranched, thin tentacle; anterior nostril located at mid-level of eye;posterior nostril opening elliptic; eyes oriented
dorsolaterally; a minute, simple tentacle on upper posterior part of eye; interorbital space very
narrow, width less than pupil diameter; mouthslightly oblique; posterior margin of maxilla justshort of, or extending slightly beyond, a verticalthrough anterior margin of pupil; uppermost anterior margin of upper jaw approximately level withlowermost margin of orbit.
Lateral line discontinuous, with an anterior
series of pored scales and a posterior series ofnotched scales; pored scale series ending below
membrane between last spine of second dorsal
fin and body; notched scale series beginning below last or penultimate pored scale and ending at
caudal-fin base; one vertical scale row between
posteriormost pored scale and notched lateral line;
body covered with ctenoid scales; size of scales
above and below lateral lines subequal; head (including maxilla, interorbital space, preopercle andopercle), pectoral-fin base, pre- and inter pelvic
region and abdomen naked; no scales between
head and first spine of first dorsal fin; fins naked,
except caudal-fin base.
First dorsal-fin origin above middle of opercle,
first spine longest, third spine shortest (1.2–1.5 in
first spine); distal margin of first dorsal-fin membrane notched; second dorsal-fin origin above fifth
pored lateral-line scale, second to fourth spine
longest (longer than first spine of first dorsal fin);third dorsal-fin origin above fifth or sixth notchedlateral-line scale; first or second soft ray longest;
pelvic-fin origin anterior to first dorsal-fin origin;
uppermost pectoral-fin ray origin below second or
third spine of first dorsal fin; pectoral fin pointed,
posterior tip of longest ray below twelfth to fourteenth spine of second dorsal fin, not reaching
to level of third dorsal-fin origin; anal-fin origin
below sixth spine of second dorsal fin; posterior
margin of caudal fin slightly rounded.
Color of mature males when fresh. Based oncolor photographs of KAUM–I. 11353 (Fig. 1A),
KAUM–I. 11354, KAUM–I. 11355, and KAUM–
I. 21659, all from Yaku-shima Island. Schematic
depiction of melanistic male coloration is given in
Figure 2. Head reddish orange with a black nar-row band, its width less than pupil diameter, fromfront of upper lip to anteroventral margin of orbit,
and black area extending from posterior marginof maxilla and near posteroventral margin of orbit
to middle and lower opercular margin; body reddish orange with several indistinct blackish andwhitish blotches mid-laterally below first andsecond dorsal fins, and two broad, black bands below third dorsal fin and caudal peduncle, the twobands joined ventrally; pectoral fin orange or yellow, with black base; pelvic fin yellowish orange
or white; dorsal fins semitransparent with poorly
defined yellow, white and blackish blotches, especially on first dorsal fin; anal fin reddish orange
anteriorly, black posteriorly; caudal fin semitransparent white or yellow, white basally.
Color of preserved male specimens. Headwhite with a black narrow band from front of upper lip to anteroventral margin, and black area
extending behind posterior margin of maxilla andposteroventral margin of orbit to middle and lower opercular margin; body white with several indistinct blackish blotches mid-laterally below firstand second dorsal fins, and a broad black bandfrom posterior end of second dorsal fin to caudalfin base; pectoral fin semitransparent, with blackbase; pelvic fin white; first and second dorsal finssemitransparent; anal fin semitransparent anteriorly, black posteriorly; caudal fin semitransparent
with white base.
Distribution. The species is currently known
from the western Pacific, with reliable records
from Yaku-shima Island (this study), Taiwan,
Hainan Island, Philippines, Indonesia, Phoenix
Island, American Samoa (type locality), Tonga,
Marianas, Marshall Islands, and Australia (Schultz
et al., 1960; Myers, 1999; Matsuura et al., 2001;
Allen and Adrim, 2003; Randall, 2005; Fricke,2009). The Yaku-shima Island specimens werecollected from rocky tidepools in depths of lessthan 3 m. In the western Pacific, most specimens
were collected from reef flats or tidepools in
depths of less than 5 m (Randall, 2005).
Remarks. The Enneapterygius hemimelasgroup was defined by Fricke (1997) as having
the following combination of characters: a small
to medium sized body; a relatively long anterior
lateral-line series, with 13–23 pore scales; a rela5

M. Meguro and H. Motomura

tively low first dorsal-fin ray in both sexes; caudal peduncle without black narrow vertical bars
or blotches; lower half of head black in mature
males; usually at least some parts of body andunpaired fins black in mature males; and 1 or 2
vertical scale rows between posteriormost pored
lateral-line scale and notched lateral line. This
group comprises E. atriceps (Jenkins, 1903), E.
bahasa, E. clea Fricke, 1997, E. hemimelas, E.
namarrgon Fricke, 1997, E. nigricauda Fricke,
1997, E. signicauda Fricke, 1997, and E. similis
Fricke, 1997.
The four male specimens from Yaku-shimaIsland were identified as belonging to the E.
hemimelas group in having the aforesaid characters, and characters of the specimens agreed
with description of E. hemimelas given by Fricke(1997). However, there are some differences
between morphometric data for E. hemimelas
given by Fricke (1997) and this study (Table 1),
although measurement methods are the same between the two. Fricke (1997) gave body width as
11.9–17.2% of SL [vs. 18.5–19.3% (mean 18.6%)
in this study], and snout length in males 4.8–6.1%
of SL [vs. 8.6–9.2% (8.9%)]. The neotype of thespecies (male) was examined by both of Fricke(1997) and this study, and data for the neotype areconsistent with those of non-type specimens of E.
hemimelas given by this study. So Fricke’s (1997)
morphometric data are most likely to be erroneous.
Enneapterygius hemimelas can be separated
from the remaining six species in the group by
the number of symphyseal mandibular pores andmature male coloration (Fricke, 1997). Enneapterygius hemimelas is easily distinguished fromE. bahasa by having a single symphyseal mandibular pore (vs. 2–8 pores in the latter; Fricke,
1997). The blackish area on the lower head of mature males of E. hemimelas is separated into twoparts: one extending from the end of the maxilla
and near the posteroventral margin of the orbit
onto the middle and lower opercular margin (andonto pectoral-fin base); and the other is a narrow
band, extending from the front of the upper lip
to the anteroventral margin of the orbit (Fricke,
1997; Figs. 1–2). However, the blackish area on
the lower head of males of all other species in6

the E. hemimelas group is not separated (Fricke,
1997). In addition, E. hemimelas has a distinct
color pattern on the posterior portion of the body.
It is distinguished from E. bahasa, E. clea, E. nigricauda, E. similis, and E. signicauda by having
a semitransparent whitish or yellowish caudal fin
in mature males (vs. fin entirely black in the first
four species, and only basal half of fin black in E.
signicauda; Fricke, 1997). Although mature malesof E. atriceps and E. namarrgon have a semitransparent caudal fin, they differ from E. hemimelas inlacking black markings on the anal fin (vs. posterior half of fin black in the latter; Figs. 1–2). The
anal-fin coloration (black posterior half of fin) of
mature male E. hemimelas is unique among the E.
hemimelas group (tips of last one or two anal-fin
rays in male E. clea being black).
Enneapterygius hemimelas was originallydescribed by Kner and Steindachner (1867) fromthe Samoa Islands. Fricke (1994) regarded E. fuligicauda (Fowler, 1946) and E. macrobrachium(Fowler, 1946), both originally described from
Aguni-jima Island, Japan, as junior synonyms of E.
hemimelas. However, Fricke (1997) re-considered
E. fuligicauda and E. macrobrachium to be juniorsynonyms of E. philippinus (Peter, 1869) and E.
rubicauda, respectively, and identified Masuda
et al.’s (1984) E. hemimelas (Japanese name:Gomafu-hebigimpo) from the Ryukyu Islands as
E. rubicauda. Recently, Chiang and Chen (2008)
synonymized E. rubicauda with E. flavoccipitis;
thus, Masuda et al.’s (1984) E. hemimelas is identified as E. flavoccipitis. The Japanese name “Gomafu-hebigimpo” (for E. hemimelas in Masuda
et al., 1984) has been applied to E. bahasa since
Shimojyo and Hayashi (2000).
Myer (1989) included the Ryukyu Islandsin the distributional range of E. hemimelas, but
he might have simply cited Masuda et al.’s E.
hemimelas (= E. flavoccipitis), and not based therecord on any other information or specimens.
Hayashi (2002) reported and illustrated a maleand female of E. hemimelas from the Ryukyu Islands. However, Hayashi’s (2002) E. hemimelasis identified here as E. bahasa in having threesymphyseal mandibular pores and a black caudal
peduncle and fin (anal fin and trunk below anterior portion of third dorsal-fin base not black).

Enneapterygius hemimelas from JapanThus, the Yaku-shima Island specimens examined
during this study represent the first record of E.
hemimelas from Japan and the northernmost record for the species.
Comparative material examined. Enneapterygius hemimelas: USNM 220068, neotype of
Tripterygium hemimelas, male, 20.6 mm SL, Fagasa Bay, Tutuila Island, American Samoa, 0–3 m
depth, 7 Oct. 1975, coll. by R. Wass.

Acknowledgments
We are grateful to Y. Haraguchi, G. Ogihara,
T. Yoshida and M. Yamashita (Kagoshima, Japan) for their curatorial assistance, J. Williams(USNM) for his kind hospitality during the firstauthor’s stay at USNM, and G. Yearsley (Hobart,
Australia) who read the initial manuscript and offered helpful comments. This study was supported
in part by a Grant-in-Aid for Scientific Research(A) (19208019) from the Japan Society for the
Promotion of Science, Tokyo, Japan, and a Grantin-Aid for Young Scientists (B) (19770067) from
the Ministry of Education, Science, Sports andCulture, Japan.

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