New Korean record of the Banded Driftfish, Psenes arafurensis (PISCES: Nomeidae)

PKU 9645, 1 specimen, 185.6 mm SL, 33°67.99′N, 127° 47.85′E, Jeju-si, Jejudo Island, Korea, August 2013; PKU 9855, 1 specimen, 194.0 mm SL, 35°32.80′N, 125° 58.99′E, Yeonggwang-gun, Jeollanam-do, Korea, September 2013; PKU 9949, 1 specimen, 199.0 mm SL, 35°95.89′N, 125° 65.04′E, Gunsan-si, Jeollabuk-do, Korea, September 2013; PKU 11311, 1 specimen, 184.8 mm SL, 33°67.99′N, 127° 47.85′E, Jeju-si, Jejudo Island, Korea, September 2014. Additional muscle tissues used for molecular analysis: FAKU 130210 (muscle tissue was transferred to PKU 12385), Oki Island, Shimane Prefecture, Japan, August 2003; FAKU 132174 (muscle tissue was transferred to PKU 12386), Chitose, Maizuru, Kyoto, Japan, November 2009.

Dorsal fin rays XI-I, 20–21; pectoral fin rays 19–20; anal fin rays III, 21–22; lateral-line scales 46–48; gill rakers 25–27; vertebrae 30–31. Meristic and morphometric characters are shown in Table 1. Body ovate, deep [41.5–44.8 % standard length (SL)], and compressed. Head large (30.5–33.3 % SL); eyes large (28.8–31.2 % of head length); snout rounded and short; two pairs of nostrils located nearer to tip of snout than to eye. Mouth terminal; upper jaw oblique, posterior margin not reaching to middle part of eye; teeth on jaws small and conical in a single row. Lateral line slightly arched, located nearer to dorsal part of body than to middle part of body. Two dorsal fins separated from each other by a narrow space; first dorsal fin beginning at base of pectoral fin, reaching anus; second dorsal fin beginning at anus, reaching anterior caudal peduncle, base length of first dorsal fin much shorter than that of second dorsal fin; two fins of similar depth. Anal fin origin slightly behind origin of second dorsal fin; spines of anal fin weak. Pectoral fin origin slightly anterior to the origin of pelvic fin, reaching to 9–10th second dorsal fin rays. Pelvic fin short, reaching to origin of second dorsal fin. Caudal fin long and strongly forked. Caudal peduncle short (4.5–4.9 % SL) and compressed. Body, head and cheeks covered with relatively large ctenoid scales.

When fresh, the dorsal surfaces of the head and body are dark purple, the ventral surfaces are gray, dorsal and caudal fin dark gray; pectoral fins translucent; pelvic fins and anal fin gray. After fixation, the dorsal surfaces of the head and body are dark brown, the ventral surfaces are gray brown, fin color as for fresh specimens.

This species is found in the tropical and subtropical seas of the Pacific, Indian and Atlantic Oceans, at depths of 150–850 m (Nakabo and Doiuchi 2013), and off Jejudo Island at the eastern margin of the Yellow Sea and the Korean Strait (present study).

These four specimens collected from Korean waters are similar to Psenes arafurensis, P. cyanophrys, P. maculatus and P. pellucidus in having a short snout (29.5–31.9 % head length) and fewer scales in the lateral line (46–48) (Nakabo and Doiuchi 2013). These four species can be distinguished easily from each other by differences in the number of lateral line scales (44–47 in P. arafurensis, 60–63 in P. cyanophrys, 67–70 in P. maculatus and 120 in P. pellucidus) and vertebrae (31 in P. arafurensis, 30–31 in P. cyanophrys, 34–38 in P. maculatus and 40–42 in P. pellucidus); the present specimens resemble P. arafurensis closely, having 44–47 lateral line scales and 31 vertebrae (Abe et al. 1963; Heemstra 1986; Nakabo and Doiuchi 2013). However, the number of dorsal fin spines in these specimens is obviously different from the original description of P. arafurensis [11 in the present specimens vs. 7 in Günther (1889)], although other counts entirely correspond with the present study. Regan (1902) pointed out the miscount of this character by Günther (1889) and indicated that the actual number is 11. According to this correction, the number of dorsal fin spines of the present specimens is also congruent with the holotype of P. arafurensis. However, several morphometric differences were observed between the present four specimens and the holotype shown by Günther (1889) and Regan (1902) (Table 1). Proportional changes with growth, especially between young and sub-adult stages, are generally known in the nomeid fishes (Haedrich 1967), and the body sizes of the present specimens (184.8–199.0 mm SL) are much larger than that of the holotype (30 mm SL). Therefore, we concluded that these morphometric differences are intraspecific variations caused by body size differences. So, to identify the species more accurately, we analyzed 562 base pairs of the mtDNA COI sequence. The mtDNA COI sequence determined in this study is nearly identical to the sequences of Indian and Japanese P. arafurensis (genetic distances, d = 0.002–0.004) (Fig. 3). Therefore, these morphological differences seem to be intraspecific variations. Since a Korean name, “A-ra-pu-ra-dom”, for P. arafurensis has already been proposed by Myoung et al. (2002), we also adopted this name for the species.

Fig. 3. Neighbor-joining tree constructed by the mitochondrial DNA COI sequences of Psenes arafurensis, with two outgroups (Psenes pellucidus and Psenopsis anomala). Numbers at branches indicate bootstrap probabilities in 1000 bootstrap replications. Bar indicates genetic distance of 0.02

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