Eumicrotremus awae

Eumicrotremus awae (Jordan and Snyder, 1902)

[Japanese name: Dango-uo]

(Figs. 1 A, B, 2A, 3A; Table 1)

Lethotremus awae Jordan & Snyder, 1902: 344 (type locality: Kominato, Awa, mouth of Tokyo Bay); Ueno, 1970:129 (Chiba, Kanagawa, and Shizuoka); Kido, 1984: 337, pl. 303-I, in part (Shizuoka to Chiba); Nakabo, 1993: 577, in part (Shizuoka to Chiba); Nakabo, 2000: 622, in part (Shizuoka to Chiba); Nakabo, 2002: 662, in part (Pacific coast of Honshu Is.); Mecklenburg & Sheiko, 2003: 11, listed, in part (Pacific coast of Honshu Is.); Nakabo & Kai, 2013: 1202, in part (Pacific coast of Honshu Is.).

Cyclopsis awae: Lindberg & Legeza, 1955: 442 (Awa, mouth of Tokyo Bay).

Materials examined. 33 specimens. CAS-SU 6971 (1 specimen, presumed holotype of Lethotremus awae, examined from photo and radiograph), near river mouth at Kominato, former Awa Province, Bay of Tokyo, coll. by Jordan and Snyder; CAS-SU 6970 (1, presumed paratype of L. awae, examined from photo and radiograph), Bay of Tokyo, coll. by Jordan and Snyder; FAKU 102873 (1), 18.9 mm SL, Heta, Shizuoka; FAKU 134183 * (1), 134725* (1), 135824 (1), PKU 55991* (mtDNA only, 1), 15.3–24.4 mm SL, Kanagawa (locality details unknown); FAKU 135362 * (1, genetic analysis only), FRLM 2425 (1), 2426 (1), 3361 (1), 4009 (1), 40382 (1), 40944* (1), 9.3–22.9 mm SL, Shima, Mie; KPM-NI 11874–11876 (3), 11886 (1), 18.8–21.5 mm SL, Jyogajima, Kanagawa; KPM-NI 13695 (1), 13696 (1), 14925 (4), 17585 (3), 14.3–22.1 mm SL, Koajiro, Misaki, Kanagawa; KPM-NI 15126 (1), 13.3 mm SL; Moroiso, Kanagawa; KPM-NI 16004 (1), 8.6 mm SL, Yokosuka, Kanagawa; KPM-NI 31619 (1), 22.2 mm SL, Manazuru, Kanagawa; KPM-NI 34207 (1), 34223 (1), 13.7–17.1 mm SL, Ito, Shizuoka.

Diagnosis. A species of Eumicrotremus with the following combination of characters: no spiny tubercles or fleshy papillae on body; anterior three mandibular pores each with a barbel-like tube; interorbital and suborbital pores usually absent; opercular flap rounded; many papillae present on ventral disk; caudal-fin relatively short, 21.0–30.5% of SL.

Description. Counts and proportional measurements are shown in Table 1. Body globose, completely naked, lacking spiny tubercles or fleshy papillae; caudal peduncle compressed. Interorbital space broad, slightly concave. Eye small, lower margin above level of snout. Two nostrils, anterior with relatively long tube, posterior with short tube. Mouth terminal, wide, slightly oblique, posterior margin of maxilla reaching to level with anterior margin of orbit (or center of orbit). Jaws with small conical teeth, arranged in three or four diagonal rows. Teeth on vomer and palatine absent. Gill slit short, its length much shorter than orbit diameter, located below origin of first dorsal fin and not reaching upper pectoral origin. Opercular flap small, rounded, directed posterodorsally.

Cephalic pores small (Fig. 2 A). Nasal canal with two pores, one anterior to nostrils and another just behind anterior nostril; interorbital canal without pores (rarely a single interorbital pore, one of four specimens of KPM-NI 14925, one of three specimens of KPM-NI 17585); postorbital canal usually with postbranchial pore, rarely supraorbital pore present anteriorly (one of four specimens of KPM-NI 14925, one of three specimens of KPM-NI 17585, KPM-NI 3 4223); branch from supraorbital canal sometimes with two small pores; infraorbital canal with two or three suborbital pores; operculomandibular canal with four mandibular pores along lower jaw, posterior three each with a barbel-like tube, anteriormost pore below tip of mandibular, second below posterior part of lower jaw, third below center of orbit, fourth at posteroventral margin of preopercle with relatively long tube. Free neuromasts reduced or indiscernable, originating from above gill slit and extending downward to level at midbody, posteriorly extending to caudal portion.

Two dorsal fins; first dorsal fin without spiny tubercles, somewhat higher in mature males than in females and immature specimens; second dorsal fin located slightly anterior to opposite anal fin, length and height almost equal, without spiny tubercles. Second dorsal and anal fins not reaching caudal fin base when depressed. Caudal fin short, rounded, its length usually shorter than pelvic disc length. Pectoral fins short, posterior tips usually not reaching level of posterior margin of pelvic disk; pectoral-fin base long, lowermost point below posterior margin of orbit. Pelvic disc large, round, slightly constricted anteriorly, with many papillae (Fig. 3 A). Anus approximately midway between posterior margin of pelvic disc and anterior origin of anal fin.

Color when fresh (Fig. 1 A, B). Coloration [from observations on FAKU 134725, 135824; KPM-NI 11874, 11875, 11876, 11886 (digital images of the latter four specimens deposited as KPM-NR 5 5941–55944 in the photographic database of KPM: http://fishpix.kahaku.go.jp/fishimage/index.html)]. Body and head coloration variable—dark brownish overall with dark brown dots, dark reddish or yellowish with irregular white markings on head, extending to base of pectoral fin, and anteriorly on bases of second dorsal and anal fins. Eye margin red or dark brown. First dorsal fin dark brown, reddish or yellowish; second dorsal, anal, caudal and pectoral fins translucent, pale reddish or yellowish. Ventral disc white, margined with yellow or dark reddish.

Color in preservative. In 70% ethanol, body and head dark, sometimes with black dots or pale irregular markings. First dorsal fin dark; second dorsal, anal, caudal and pectoral fins translucent. Ventral disc white, with dark margin.

Distribution. Specimen records indicated a distribution along the Pacific coast of Honshu Is., from Chiba westward to Mie (Fig. 4).

Remarks. Eumicrotremus awae was originally described by Jordan and Snyder (1902) in the genus Lethotremus, on the basis of the holotype, CAS-SU 6539 and other specimens (no catalog numbers given in the original description). According to Mecklenburg and Sheiko (2003), CAS-SU 6539 is now missing and CAS-SU 6971 may, in fact, be the missing holotype (suggested by notes in the collection database). Earlier, Böhlke (1953) had listed CAS-SU 6971 and 6970 as holotype and paratype of E. awae, respectively. Although the type status of CAS-SU 6971 remains unclear, both CAS-SU 6971 and 6970 had many ventral disk papillae, and lacked interorbital and supraorbital pores, being consistent with E. awae (see Jordan and Snyder, 1902). In addition, the type specimens, including that initially listed as CAS-SU 6539 in the original description, were all collected from Bay of Tokyo, being only included in the established distributional range of E. awae.

The description of Cyclopsis awae given by Lindberg & Legeza (1955) was partly based on Jordan & Snyder (1902), but suggested also that some of the type specimens of Cyclopsis tentacularis Popov 1930 from the Sea of Okhotsk may have been the former species. Probably following Lindberg and Legza (1955), Parin et al. (2002, 2014) listed E. awae from the southern Kuril Islands. However, the specimens examined by Lindberg and Legeza (1955) were not available during the present study and the record from the Sea of Okhotsk is doubtful due to the distance of that region from the area populated by E. awae.

In his review of lumpsuckers, Ueno (1970) described L. awae on the basis of nine specimens collected from Chiba, Kanagawa and Shizuoka, the Pacific coast of Honshu Is. According to his figure, the specimens had many papillae on the ventral disk, a supraorbital pore and no interorbital pores, characters consistent with the present specimens of E. awae. In addition, Ueno’s (1970) color plates of specimens (apparently> 20 mm SL) had no dark spot above anal fin origin, which also supported their identity as E. awae.

Various authors have recorded “ Lethotremus awae ” from (or near) the established range of the presently recognized E. awae [Suzuki & Kataoka (1997), from Mie; Zama (2001), from Miyagi; Nakabo (2002), from the Pacific coast of Honshu Is.; Aizawa (2003), from Chiba; Shiogaki et al. (2004), from Aomori; Senou et al. (2006), from Sagami Bay], although these reports cannot now be attributed with certainty to E. awae as recognized here because of the lack of definitive characters. Abe and Sato (2009) also reported the reproductive biology of E. awae in Shizugawa Bay, Pacific coast of northern Honshu Is., but no presently recognized species diagnostic characters could be determined from their description and photos. Similarly, the short descriptions of L. awae in Kido (1984), Nakabo (1993, 2000, 2002) and Nakabo and Kai (2013) did not include recognizable definitive characters, the distribution ranges given extending over those of the three species recognized here.