A total of approximately 275 species in about 70 genera are recognized in the family Cottidae, order Scorpaeniformes (Nelson, 2006); of those, 33 species in 18 genera have been recognized in Korea (Kim et al., 2005). The genus Icelus Krøyer, 1845, is distinguished by the presence of a pelvic fin with one spine and three soft rays, small conical teeth on both jaws, vomer, and palatines. Four preopercular spines are present. Lateral line scales are tubular and flattened on lateral and medial surfaces (Nelson, 1984). Icelus comprises 17 species worldwide, with three species previously recorded in Korea (Kim et al., 2005): Icelus cataphractus Pavlenko, 1910, Icelus ochotensis Schmidt, 1927, and Icelus stenosomus Andriashev, 1937.
In this study, three specimens of Icelus toyamensis Matsubara and Iwai, 1951, were collected from Korea for the first time; we here describe the species on the basis of these specimens. Methods for counts and measurements follow those of Hubbs and Lagler (2004); the numbers of fin rays and vertebrae were counted by soft X-ray (Hitex HA-100; Hitex Co., Tokyo, Japan). The specimens are deposited in the National Institute of Biological Resources (NIBR), Korea.
Family Cottidae Bonaparte, 1832
Genus Icelus Krøyer , 1845
1*Icelus toyamensis (Matsubara and Iwai, 1951) (Table 1, Fig. 1)
Ricuzenius toyamensis Matsubara and Iwai, 1951: 87, figs. 1-3 (type locality: Off Uozu, Japan); Masuda et al., 1984: 324.
Icelus toyamensis: Nakabo, 2002: 633; Tsuruoka et al., 2006: 51; Shinohara et al., 2011: 44.
Material examined. 2 specimens, 77.7-117.7 mm standard
length (SL), Gyeongsanbuk-do, Uljin-gun, Hupo-myeon, Hupo-ri, Hupo fishing ports, 18 Mar 2009, NIBR-P 4791. 1 specimen, 90.1 mm SL, Gangwon-do, Goseong-gun, Jukwangmyeon, Oho-ri, 18 Mar 2007, Kim AR, NIBR-P 0000016324, from a deep sea water pump at 300 m water depth.
Comparative material examined. Icelus cataphractus, 1 specimen, 141.18 mm SL, Gangwon-do, Yangyang, 2 Dec 2010, PKU 5044 (Fig. 2).
Description. Counts and measurements are shown in Table 1. Body slightly compressed; head large and slightly depressed. Snout short and blunt. Mouth terminal; anterior tip of lower jaw projecting further than anterior tip of upper jaw. Conical teeth on both jaws; small teeth on vomer and palatines. Eyes large; interorbital space very narrow and flat. Pair of small sharp nasal spines directed posterodorsally on anterior nostril. Pair of strong spines in occipital region. Four preopercular spines; uppermost spine simple, sharp, slightly curved upward, and longer than the other three spines, which are short. Gill rakers 2+9; those on the lower limb short, rounded or tubular in shape, and with spiny processes on upper surface. Small spines scattered on suborbital, cheek, and nuchal regions. Origin of dorsal fin vertically above upper end of gill opening; dorsal fin extends until above 32nd-33rd lateral line scale; dorsal spine rays and soft rays smoothly separated. Pectoral fin relatively long, extending posteriorly to below 5th-6th dorsal fin ray. Pelvic fin small; begins under lower base of pectoral fin and extends to anus. Caudal fin slightly rounded and truncate. Small scattered ctenoids; rare on dorsal and ventral sides. Lateral line scales tubular and sparse, extending from opercular flap to base of caudal fin.
Coloration. After fixation in formalin: body and head uniformly blackish brown; snout and circumorbital regions black; posterior margin of dorsal fin spines blackish, with
several irregular dark brown bars on dorsal fin soft rays, pectoral fin rays, and caudal fin rays (Fig. 1).
Distribution. Icelus toyamensis was collected from Korea, in Goseong, Gangwon-do and Hupo, Gyeongsangbuk-do. The species also occurs in the Niigata and Ishikawa prefectures, Japan (Nakabo, 2002).
Remarks. The specimens collected in Goseong, Gangwondo and Hupo, Gyeongsangbuk-do, belong to the genus Icelus, based on the presence of teeth on the vomer and palatine, the presence of small spines on occipital, cheek, and nuchal regions (Krøyer, 1845; Matsubara and Iwai, 1951; Nakabo, 2002), and the presence of small scattered ctenoids on the dorsal and ventral sides of the body (Matsubara and Iwai, 1951; Nakabo, 2002). When compared with the original description (Matsubara and Iwai, 1951) and other references (Watanabe, 1981; Nakabo, 2002), most of the meristic characters correspond to those described by other authors, except for the number of caudal fin rays and the number of lower limbs of the gill rakers. These differences are thought to be related to geographic variations, but the correspondence of variations to geographic provinces requires further clarification.
When compared with the congeneric species I. cataphractus, our specimens of I. toyamensis are similar in terms of counts and measurements, but differ in terms of morphological characteristics. These are distinguished by the absence of spinous scales on the base of the dorsal fin in I. toyamensis vs. their presence in I. cataphractus (Fig. 3). Also, the gill rakers in I. toyamensis are short, tubular, and relatively broad, whereas those in I. cataphractus are large, circular, and relatively narrow (Fig. 4). Lastly, the uppermost preopercular spine in I. toyamensis is sharp and simple, whereas the preopercular spine in I. cataphractus is bifurcate (Fig. 5). Icelus ochotensis and I. stenosomus are distinguished from I. toyamensis by the distributions of body scales (scattered in I. toyamensis vs. arranged in rows in I. ochotensis and I. stenosomus) (Nelson, 1984; Nakabo, 2002; Kim et al., 2005). We propose a new Korean name for I. toyamensis, “Min-julga- shi-hoet-dae.”
Korean name: 1*민줄가시횟대