Mem. Fac. Fish. Kagoshima Univ.,Vol. 62, pp. 7~10 (2013)

First record of a unicornfish, Naso tergus (Perciformes:Acanthuridae), from the Philippines
Mizuki Matsunuma 1*, Satokuni Tashiro 2, Ulysses B. Alama 3 and Hiroyuki Motomura 1

Key words: Distribution, Iloilo, Panay Island

Abstract
A single specimen of Naso tergus Ho, Shen and Chang, 2011 (Acanthuridae), having previously been known only from Taiwan andthe Ryukyu Islands, southern Japan, was collected off Iloilo Province (Panay Island), the Philippines. The present specimen represents
the first record of N. tergus from the Philippines and the southernmost record for the species. It suggests that N. tergus is widelydistributed in the northwestern Pacific Ocean. The present specimen is described in detail and morphological variations of the species
are mentioned.

The acanthurid genus, Naso, comprises 20 species fromIndo-Pacific region

1–2). One of these, Naso tergus, wasInstitutional code used in this study is as follows: KAUM —The Kagoshima University Museum, Kagoshima, Japan.

originally described in 2011 by Ho et al. 2) on the basis of
13 specimens from Taiwan. Matsunuma and Motomura 3)

Results and Discussion

subsequently reported the species from Nakano-shima islandin the Tokara Islands, southern Japan, on the basis of a single

Naso tergus Ho, Shen and Chang, 2011

specimen. No other record of the species has been reported.

(Figs. 1–2; Table 1)

A single specimen of N. tergus was obtained at the Iloilo
Central Market in Iloilo City, Panay Island, the Philippines,

Naso tergus Ho, Shen and Chang, 2011: 205, figs. 1–4

during a marine ichthyofaunal survey of the Iloilo Province(type locality: off Nanfangao, Ilan, northeastern Taiwan);in August 2013, led by the University of the Philippines

Matsunuma and Motomura, 2013: 103, figs. 1–2, 4 (Nakano-Visaya, the Research Institute for Humanity and Nature, andshima island, Tokara Islands, Japan; description).

the Kagoshima University Museum. The present specimen
is described herein as the first record of the species from theSpecimen examined. KAUM–I. 56004, 211.9 mm SL,
off Iloilo (Panay Island), the Philippines (purchased at Iloilo

Philippines.

Central Market in Iloilo City), 20 August 2013, H. Motomura,

Material and Methods

M. Matsunuma, S. Tashiro, N. Muto, and Y. Ogata.
4)

andDescription. Meristics and morphometrics expressed as

Ho et al. 2), and were made on the left side. Standard length

percentage of SL are shown in Table 1. Body moderately

is abbreviated as SL. Curatorial procedures for the newly

elongated and compressed, lateral profile spindle-like, deepest

Counts and measurements followed Randall and Bell5)

collected specimen followed Motomura and Ishikawa . The

at midpoint of body; head relatively large, dorsal profile

鹿児島大学総合研究博物館 (The Kagoshima University Museum, 1-21-30 Korimoto, Kagoshima 890-0065, Japan)
鹿児島大学大学院水産学研究科 (The Graduate School of Fisheries, Kagoshima University, 4-50-20 Shimoarata, Kagoshima 890-0056, Japan)
3
フィリピン大学ビサヤ校自然史博物館 (Museum of Natural Science, University of the Philippines Visayas, 5023 Miag-ao, Iloilo, Philippines)*
Corresponding author, E-mail: k1139853@kadai.jp
12

8Mem. Fac. Fish. Kagoshima Univ., 62 (2013)

Fig. 1. Fresh specimen of Naso tergus, KAUM–I. 56004, 211.9 mm standard length, from off Iloilo (Panay Island), the Philippines (obtainedat Iloilo Central Market).

gradually sloping. Mouth relatively small, upper jaw slightly

Coloration when fresh. Head and body uniformly lightprojecting; gape almost horizontal; lips narrow; teeth uniserial,brown, paler ventrally (Fig. 1). Lips pale gray. Eye dark

slender, and lanceolate; approximately 80 (partly broken) teeth

yellowish-brown; iris black. Tongue and gill rakers creamy

on both jaws; tongue broadly rounded. A deep oblique groove

white. Dorsal-fin rays same coloration as body; ground color

on snout from in front of middle of eye to nearly two-thirdsof fin membrane pale gray, dark brownish marginally, mottled

distance to front of mouth; nostrils very small, anterior nostril

with light brown. Anal fin similar to dorsal fin but slightly

with a low membranous rim and a small triangular posterior

paler. Pectoral fin semi-translucent. Pelvic-fin spine same

flap.

color as ventral portion of body; membrane grayish-white,

Scales very small, close-set, each with an elevated dense
patch of posteriorly directed spinules; body and headbrownish distally. Caudal fin uniformly light yellowish-brown,
pale marginally. Peduncular plates pale reddish-brown.

completely scaled except for lips, opercular membrane, andRemarks. The present specimen from the Philippines

around anterior nostril. Lateral line on upper side of body,

is identified here as Naso tergus on the basis of following

running along contour of back.

combination of characters: six dorsal-fin spines; two bony

Dorsal-fin origin just above upper end of gill opening; firstplates on the caudal peduncle; eye diameter 7.3% of SL;

dorsal-fin spine slightly longer than sixth dorsal-fin spine.

body depth 35.2% SL (2.8 in SL); and the body uniformly

Anal-fin origin below fifth dorsal-fin spine base; length ofbrownish. These characters of the present specimen agreed

first spine subequal to that of second spine; height of soft-

with the diagnostic characters of N. tergus given by Ho et al. 2),

rayed portion almost similar to that of dorsal fin. Upper end of

except for a slightly larger eye (its diameter 7.3% of SL in thepectoral-fin base slightly anterior to a vertical through dorsal-

present specimen vs. 6.3–7.2% of SL in Ho et al. 2)).

fin origin; upper 2 and lowermost rays unbranched, fourth ray

Some morphometric differences are found between thelongest. Pelvic-fin origin below first dorsal-fin spine base; firstpresent specimen of N. tergus and specimens from Taiwan

soft-ray longest, its tip reaching first anal-fin spine base whenand Japan given by Ho et al. 2) and Matsunuma et al. 3)

depressed. Caudal fin slightly emarginate.

respectively, e.g., slightly longer upper-jaw length of 5.9%

Two elliptical bony plates on each side of caudal peduncle;of SL (vs. 4.9–5.7%), suborbital width 10.1% of SL (vs.

both plates approximately equal size; a keel-like spine

8.6–10.0%), and second dorsal-fin spine length 11.2% ofprojecting laterally; shape of spine trapezoid or low ridge

SL (vs. 8.6–10.8%) (Table 1). These minor differences arewithout pointed tip.

regarded here as intraspecific variation, most likely related to9Matsunuma et al.: First record of Naso tergus from Philippines

Table 1. Meristics and morphometrics, as percentages of standard length, of Naso tergus.

Locality
Number of specimens

Matsunuma andPresent specimen

Ho et al. 2)

Philippines

TaiwanJapan

1

13

1

VI, 28VI, 26–30

VI, 27II, 28II, 26–28

II, 27

Motomura 3)

Meristics
Dorsal-fin rays
Anal-fin rays
1ii + 13 + i = 16

16

ii + 13 + i = 162

4 + 11 = 15

4 + 11–13 = 15–17

4 + 11 = 15

Standard length (SL, mm)

211.9

275–335

363.0

Head length

25.7

24.6–26.6

23.7

Body depth

35.2

34.4–36.8

31.2

Body width

13.8

13.3–15.2

12.5

Pre-dorsal-fin length

26.8

25.2–28.7

25.5

Pre-pectoral-fin length

24.7

23.5–27.6

23.2

Pre-pelvic-fin length

27.9

29.3–32.2

27.6

Pre-anal-fin length

38.9

38.6–41.3

36.6

Snout length

13.7

13.2–14.1

13.4

Eye diameter

7.3

6.3–7.2

6.0

Interorbital width

9.2

8.9–10.0

9.3

Upper-jaw length

5.9

4.9–5.7

5.5

Suborbital width

10.1

8.6–10.0

8.1

1st dorsal-fin spine length—

5.5–12.7

9.4

2nd dorsal-fin spine length

11.2

8.6–10.8

9.2

3rd dorsal-fin spine length—

8.2–10.7

8.9

4th dorsal-fin spine length

11.0

8.1–10.3

9.0

5th dorsal-fin spine length

10.1

8.8–11.7—

6th dorsal-fin spine length

9.3

8.4–9.7

8.6

Pectoral-fin length

16.4

14.0–15.7

15.8

Pelvic-fin spine length

11.1

8.0–10.5

9.8

1st anal-fin spine length

7.8

3.6–7.9

6.1

2nd anal-fin spine length—

5.6–8.6

6.6

Caudal-peduncle length

9.0

7.8–9.9

8.2

Caudal-peduncle depth

4.2

4.3–5.3

4.0

Caudal-peduncle width

5.2

5.4–6.7

5.9

Caudal-fork length

18.4

16.2–18.015.5

Caudal-fin length

28.4

23.0–28.1

25.7

Pectoral-fin rays
Gill rakers

Morphometrics (% SL)

12Upper unbranched rays + branched rays + lower unbranched rays = total rays on left side of body; Rakers on upper limb + rakers on lower limb =total rakers

10Mem. Fac. Fish. Kagoshima Univ., 62 (2013)

Acknowledgments

fish growth, because the Philippine specimen is smaller (211.9mm SL) than the previously recorded specimens (275–363.0
Naso tergus has previously been recorded only fromTaiwan and JapanWe are especially grateful to F. Muto (Tokai University,Japan), N. Muto and Y. Ogata (Research Institute formm SL).
2–3)

Humanity and Nature, Japan), and R. Babaran, D. Paguntalan,. Accordingly, the present specimen fromS. Garibay, V. Garcia, E. Abunal, and L. Mooc (UniversityIloilo, Panay Island, represents the first record of N. tergusof the Philippines Visayas, Philippines) for their assistancefrom the Philippines and the southernmost record for theduring our survey in Iloilo. We thank M. Meguro, T. Yoshida,species (Fig. 2). This study suggests that N. tergus is moreB. Jeong, Y. Fukui, and H. Hata (Kagoshima University,widely distributed in the northwestern Pacific Ocean thanJapan) and Y. Haraguchi and other volunteers of KAUM for

was first thought. Regarding the dispersal of this species,

their curatorial assistance, and G. Yearsley (Hobart, Australia)

we propose that N. tergus populated Taiwan and Japan fromfor reading the manuscript and his helpful comments. This

the Philippines via the Kuroshio Current. The specimens

study was supported in part by Grants-in-Aid for Scientificcollected from Taiwanese waters represent various life stages,Research (B, 24370041 and C, 23580259) from the Japansuggesting that the Taiwanese population reproduces locally.

Society for the Promotion of Science, Tokyo, Japan (JSPS),However, only a single specimen, large in size, has beena Grant-in-Aid for Young Scientists (B, 19770067) fromcollected from Japan, and this might indicate that the species

the Ministry of Education, Science, Sports and Culture,

does not reproduce in Japanese waters. Further specimens

Tokyo, Japan, JSPS Asian Core Program “Establishment offrom the Philippines and other Southeast Asian countries

Research and Education Network on Coastal Marine Scienceare required to further assess the distribution and biologicalin Southeast Asia”, JSPS International Training Program

aspects of the species.

“Protect Diversity of Bioresources in the Tropical Area”, andthe Coastal Area Capability Enhancement in Southeast Asia
Project of the Research Institute for Humanity and Nature,
Kyoto, Japan.

References
1) Randall, J. E. (2002). Surgeofishes of Hawai’i and the world.
Mutual Publishing, Honolulu. pp. x + 123 + ii.
2) Ho, H.-C., Shen, K.-N. and Chang, C.-W. (2011). A new speciesof the unicornfish genus Naso (Teleostei: Acanthuridae) fromTaiwan, with comments on its phylogenetic relationship. Raffles
Bull. Zool., 59 (2): 205–211.
3) Matsunuma, M. and Motomura, H. (2013). First Japanese recordof Naso tergus (Perciformes: Acanthuridae) from the Tokara
Islands, southern Japan. Japan. J. Ichthyol., 60 (2): 103–110. (inJapanese with English abstract).
4) Randall, J. E. and Bell, L. J. (1992). Naso caesius, a new
acanthurid fish from the central Pacific. Pac. Sci., 46 (3): 344–352, pl. 1.
5) Motomura, H. and Ishikawa, S. (eds.). (2013). Fish collection
Fig. 2. Localities of previous records (circles) and present specimen(star) of Naso tergus.

building and procedures manual. English edition. The Kagoshima
University Museum, Kagoshima and the Research Institute for
Humanity and Nature, Kyoto. pp. 70. (Available at http://www.
museum.kagoshima-u.ac.jp/staff/motomura/dl_en.html)