New Record of a Rare Hypogean Gobiid, Luciogobius pallidusfrom Jeju Island, Korea

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INTRODUCTION

The small gobiid genus Luciogobius Gill, 1859, is mainly characterized by having the following characters:

elongated, worm-like body with a depressed small head;

small eyes, or degenerated and embedded beneath skin, located dorsally; absence of the first dorsal fin (and even the second dorsal fin in L. adapel); and absence, or reduc- ed coverage of scales on body (Kanagawa et al., 2011).

In this genus, 16 species have been recognized as valid and most of them are occurred in interstitial habitats of gravel beaches or river mouth from the East Asia. From the Korean waters, only four species have been reported as follow to date: L. grandis Arai, 1970, L. guttatus Gill, 1859, L. koma (Snyder, 1909), and L. saikaiensis Dôtu, 1957 (Kim et al., 2005), although two unrecorded Lucio- gobius fishes (i.e., L. elongatus and L. platcephalus) were already found from the southeastern coast of the Korean Peninsula (pers. comm. S.H. Choi).

During a recent ichthyofaunal survey of Jeju Island, Korea, I obtained an unique Luciogobius species with yellowish orange coloration from the upper rocky inter- tidal zone close to springwaters located at the southern coast of the island. It was readily identified as a rare hy- pogean gobiid, Luciogobius pallidus which has been re- corded from only the Japanese waters to date by its uni- que body coloration (Akihito et al., 2002; Proudlove,

2006), representing as the first record from Korea and also as the westernmost record of the world. In this study, I describe Luciogobius pallidus as the first hypogean fish from Korea.

MATERIALS AND METHODS

All specimens of Luciogobius pallidus were collected from the rocky intertidal zone close to springwaters with bare hands or small hand nets at low tide during a survey on excavating project of Korean indigenous fish species in Jeju Island. They were fixed in 5~7% formalin after taking photographs and transfered into 75% ethanol for long-term preservation. Vouchers are deposited at the National Institute of Biological Resources (NIBR-P), Korea. Counts and measurements follow those of Hubbs and Lagler (1958). The cephalic sensory canal system was observed by stained specimens with cyanine blue, following those of Akihito et al. (2002).

Luciogobius pallidus Regan, 1940 (New Korean name: Ju-hong-mi-ggeun-mang-dug)

(Figs. 1~2; Table 1)

Luciogobius pallidus Regan, 1940: 465 (type locality: an artesian well, Japan); Akihito et al., 1984: 283; Honma, 1991: 25; Yoshida and Dotsu, 1997: 628; Romero and Paulson, 2001: 35; Proudlove, 2006: 194.

Materials examined. NIBR-P13719, 4 specimens, 31.2

~53.6 mm in standard length (SL), Haye-dong, Seogwi-

New Record of a Rare Hypogean Gobiid, Luciogobius pallidus from Jeju Island, Korea

By Byung-Jik Kim

Animal Resources Division, National Institute of Biological Resources, Incheon 404-708, Korea

ABSTRACT A hypogean gobiid, Luciogobius pallidus was described as the first record from Korea and also as the westernmost record of the species from the world, based on four specimens (31.2~

53.6 mm SL) collected from Jeju Island, Korea. The species is characterized by having yellowish orange body color with I, 10

rays, and 36 vertebrae as well as small embedded eyes beneath the skin. A new Korean name, “Ju- hong-mi-ggeun-mang-dug” was proposed for the species.

Key words : Gobiidae, Luciogobius pallidus, new Korean record, hypogean fish, Jeju Island

*Corresponding author: Byung-Jik Kim Tel: 82-32-590-7360, Fax: 82-32-590-7250, E-mail: [email protected]

Accepted: December 21, 2012

http://www.fishkorea.or.kr

po-si, Jeju-do, Korea, 8 June 2011, collected by B.J. Kim, S.H. Choi, and H.G. Cho.

Description. Second dorsal fin rays I, 10~11; anal fin rays I, 10~12; pectoral fin rays 13~15 (mainly 15); pe- lvic fin rays I, 5; principal caudal rays 17; vertebrae 36.

First dorsal and anal pterygiophores inserted between 18th and 19h vertebrae; last dorsal and anal pterygioph- ores inserted between 25th and 26th vertebrae; total dor- sal and anal pterygiophores 12 and 11, respectively. Body proportion as % SL: head length 19.4~22.8 (mean 21.2) head depth 12.5~15.0 (13.9); upper jaw length 7.7~10.2 (8.7); snout length 5.1~5.8 (5.4); interorbital width 3.4

~5.4 (4.0); body depth 9.6~10.8 (10.1); length of long- est pectoral fin ray 11.8~13.6 (12.9); predorsal length 60.0~69.9 (67.3); length of second dorsal fin base 14.6

of anal fin base 17.0~17.9 (17.5); length of longest anal fin ray 8.8~11.7 (10.7); caudal peduncle depth 9.3~10.8 (10.3); caudal peduncle depth 14.8~17.4 (16.0).

Body cylinderical and elongate, gradually compressed posteriorly. Head relatively large, its length about one fifths of SL and depressed. Mouth terminal; maxilla ex- tending posterior to a vertical at posterior margin of orbit.

Both jaws with 3 to 4 rows of conical teeth arranged irreg- ularly, those on outer row larger, weakly curved inward- ly. Gill opening narrow, extending ventrally to lower end of pectoral fin. Nares two and well separated; anterior one a short tube, its tip reaching to upper lip and posteri- or simple pore close to eye. Eye small and degenerated, embedded beneath skin; clearly visible when fresh, and obscured by bleaching after fixation. Interorbital region relatively wide and flat. A longitudinal thin dermal ridge running from snout to cheek below eye. Occipital region slightly bulged dorso-laterally. First dorsal fin absent.

Second dorsal fin origin nearly at a same vertical of anal fin origin; 7th rays longest in both second dorsal and anal fins. Posterior margin of second dorsal and anal fins re- latively round. Pectoral fin round, lacking any free soft rays on upper and lower ends. Pelvic fins fused, forming a small sucker with thin membranous frenum. Caudal fin relatively large and round. No scales on head and body.

Cephalic sensory system as shown in Fig. 1. Sensory canal and pore absent. Pit organs arranged sparsely, form- ing some longitudinal rows on occipital region, cheek and mandible; two transverse short rows present on opercle.

Color when fresh (Fig. 2). Head and body yellowish orange with distal margin of all fins translucent and ven- tral sides of body slightly paler.

Color after preservation: Yellowish orange on head and body completely faded; ground color of head and body pale brownish with small brownish dots scattered restrict to upper region of head and body. Ventral region of head and body anterior to anal fin without any brown- ish dots. Lower half of second dorsal and basal region of caudal fins with minute brownish dots. Anal and pel- vic fins transparent without any brownish dots.

Ecological notes. All specimens were collected at the upper rocky intertidal zone close to springwaters. It was found beneath gravel substrates composed of coarse sand and small pebbles where freshwater springs flow from gaps between the pebbles. Three gobiid fishes, Chasmi- chthys dolichognathus, Mugilogobius abei, and Luciogo- bius guttatus were coexisted around the collection site of L. pallidus.

Distribution. From Korea, it is known only from the southern coast of Jeju Island (present study). The species shows relatively wide distribution (Shizuoka Pref., Mie Pref., Wakayama Pref., Kochi Pref., Ehime Pref., Shikoku Pref., Kumamoto Pref., Yamauchi Pref., Nagasaki Pref.;

Fig. 1. Dorsal (A), lateral (B), and ventral (C) views of sensory papil- lae in Luciogobius pallidus, NIBR-P13719, 53.6 mm SL. AN and PN, anterior and posterior nostrils, respectively. Arrow shows point where gill membrane attached to isthmus and bar indicates 2 mm. Dotted line shows subcutaneous eyeball and some papillae of opposite side ommit- ted.

(B)

(C)

AN PN

Yoshida and Akihito, 1997; Akihito et al., 2002).

Remarks. Up to date, it has been known that only five species of Luciogobius have small eyes embedded ben- eath the skin as follows: L. albus Regan, 1940, L. pallidus Regan, 1940, L. dormitoris Shiogaki and Dotsu, 1976, L. fonticola Kanagawa, Itai and Senou, 2011, and L. flu- vialis Kanagawa, Itai and Senou, 2011 (Romero and Pau- lson, 2001; Kanagawa et al., 2011).

Luciogobius specimens collected from the Jeju Island, Korea is readily differentiated from L. albus and L. fon- ticola by having the larger number of second dorsal fin

rays (I, 10~11 vs. I, 7~9), and from L. fluvialis by hav- ing the larger number of vertebrae (36 vs. 31~33). Alth- ough it is most similar to L. dormitoris in having common diagnostic characters, L. pallidus differs from the latter by having the thinner the body depth (15.6~26.8 vs. 7.6 in SL). Thus, the present specimens were finally identi- fied as Luciogobius pallidus which have been known from the western Japan only to date and also well coin- cided with the result of the previous works as well as the diagnostics of syntypes of the species (Table 1).

Comparative materials. Luciogobius pallidus: ZUMT

Fig. 2. Fresh male (A: upper, 41.2 mm SL) and female (A: lower, 53.6 mm SL), and live specimens (B, C) of Luciogobius pallidus (NIBR- P13719) collected from Jeju Island, Korea.

Table 1. Comparion of diagnostic characters between Korean specimens and previous reports of Luciogobius pallidus Luciogobius pallidus

Jeju Island, Korea Syntypes Kanagawa et al. (2011)

Standard length (mm) 31.2~53.6 (n==4) 29.4~53.8 (n==3) -

Second dorsal fin rays I, 10~11 I, 9 I, 10~11

Anal fin rays I, 10~12 I, 9 I, 10 (10~11)

Pectoral fin rays 13~15 13 13 (13~15)

Pelvic fin rays I, 5 I, 5 I, 5

Vertebrae 36 35 36 (35~37)

Eye embedded beneath skin Yes Yes Yes

A

B C

sian well, Japan.

ACKNOWLEDGEMENTS

I thank to Dr. Seung-Ho Choi (Institute of Biodiversity Research, Jeonju), and Mr. Hyun-Geun Cho (Kunsan National University) for their assistance of field survey and especially grateful to Dr. K. Sakamoto (ZUMT) for giving opportunity to examine the type specimens of Luciogobius pallidus Regan.

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Akihito, Prince, K. Sakamoto, Y. Ikeda and K. Sugiyama.

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제주도에서 처음 발견된 지하수계 서식 희귀 망둑어류 한국미기록종, Luciogoius pallidus

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