Luciogobius platycephalus Shiogaki & Dotsu, 1976

Koreeda, Reo, Maeda, Ken & Motomura, Hiroyuki, 2023, A new subtropical species of goby of the genus Luciogobius (Gobiidae) from southwestern Japan, Zootaxa 5361 (3), pp. 390-408 : 400-404

Luciogobius platycephalus Shiogaki & Dotsu, 1976

[New English name: Spear Earthworm Goby; standard Japanese name: Yari-mimizuhaze]

Figure 9 , Table 2

Luciogobius platycephalus Shiogaki & Dotsu, 1976: 126 , figs. 1–2 (type locality: Kawahara, Sanwa, Nagasaki Pref., Japan); Shiogaki & Dotsu, 1977: 43, figs. 1, 2BC, 4, 5 (Shimabara Pen., Nagasaki Pref., Japan); Akihito, 1984: 270, pl. 255, fig. E; Akihito et al., 1993: 1009, 1091; Aizawa, 1997: 621, fig. 4 (Minma, Aomori Pref., Japan); Aizawa, 2006: 14, unnumbered fig. (Nagasaki Pref., Japan); Akihito et al., 2000: 1146, 1277; Takagi et al., 2010: 126, unnumbered fig. (Morode Bay, Ehime Pref., Japan); Akihito et al., 2013: 1376, 2116; Tsuji, 2013: 5, fig. 8 (Nezumi-jima island, Ehime Pref., Japan); Cho & Choi, 2014: 22, fig. 1; Koreeda et al., 2020: 357, figs. 2B, 3A–F; Yamashita & Suga, 2021: 197; Tashiro et al., 2022: 252, unnumbered fig.; Koreeda et al., 2023: 9 , fig. 3A, B (Miyazaki Pref., Japan).

Luciogobius elongatus (not of Regan): Masuda & Kobayashi, 1994: 326, fig. 6.

Luciogobius platycephalus A: Yamada et al., 2009: 6 (Horonai, Aomori Pref.; Shionomisaki, Wakayama Pref.; Kamaura and Oki Is., Shimane Pref.; Naga-shima I., Yamaguchi Pref.; Fukue and Tsushima Is., Nagasaki Pref., Japan).

Non-type specimens. 85 specimens (14.9–61.4 mm SL) from Japan. Sado-shima island (Niigata Pref.): KAUM– I. 180989 , 54.0 mm SL, KAUM–I. 180990 , 49.7 mm SL, collected by S. Fujii, 18 July, 2022, Kitaebisu, Sado (38°06′00″N, 138°15′40″E). Nagasaki Peninsula (Nagasaki Pref.): KAUM–I. 166320 , 60.9 mm SL, collected by T. Iwasaki, 22 Feb. 2022, Kawara Coast, Miyazaki (32°37′35″N, 129°50′07″E). Kagoshima Bay (Kagoshima Pref.): KAUM–I. 132026–132031 , 6 specimens, 32.4–38.3 mm SL, collected by R. Koreeda, 14 July 2019; KAUM– I. 134456–134460 , 37.4–55.3 mm SL, collected by R. Koreeda, R. Furuhashi, T. Akaike & N. Shimizu, 13 Nov. 2019; KAUM–I. 139181–139189 , 139191–139194 , 16.5–53.9 mm SL, 13 specimens, collected by R. Koreeda & N. Shimizu, 1 Feb. 2020; KAUM–I. 139743 , 18.6 mm SL, KAUM–I. 139744 , 14.9 mm SL, KAUM–I. 139794 , 43.8 mm SL, collected by R. Koreeda, 14 Feb. 2020; KAUM–I. 140931 , 23.6 mm SL, collected by R. Koreeda, 15 Feb. 2020; KAUM–I. 153336 , 55.7 mm SL, KAUM–I. 153351–153355 , 5 specimens, 48.7–58.9 mm SL, collected by R. Koreeda & T. Akaike, 13 Feb. 2021, Shirahama Beach , Wakimoto, Aira (31°40′58″N, 130°36′35″E); KAUM– I. 184695 , 36.4 mm SL, collected by R. Koreeda, 13 June. 2021, Kiiresesekushi, Kagoshima City (31°25′54″N, 130°31′16″E). Satsuma Peninsula (Kagoshima Pref.): KAUM–I. 141761 , 47.5 mm SL, collected by R. Koreeda, 28 Mar. 2020, gravel beach at Taniyama River mouth, Nomaike , Kasasa , Minamisatsuma (31°25′52″N, 130°09′16″E); KAUM –I. 138918 , 17.1 mm SL, collected by R. Koreeda & N. Shimizu, 13 Jan. 2021, coast near Hinokami Park , Hinokami-misaki , Makurazaki (31°14′59″N, 130°16′43″E); KAUM–I. 139487 , 21.3 mm SL, collected by T.Akaike, 9 Feb. 2021, west coast of Hinokami Cape , Hinokami-misaki , Makurazaki (31°14′57″N, 130°16′29″E); KAUM–I. 157935–157937 , 3 specimens, 29.9–61.4 mm SL, KAUM–I. 158034 , 34.8 mm SL, KAUM–I. 158035 , 32.0 mm SL, rocky coast of Arakawa, Ichikikushikino (31°44′00″N, 130°14′24″E); KAUM–I. 142255–142260 , 142273–142275 , 142312–142313 , 12 specimens, 24.7–49.8 mm SL, collected by R. Koreeda, R. Furuhashi, N. Shimizu & S. Kano, 25 Apr. 2020, gravel beach at Arakawa River mouth, Ichikikushikino (31°44′19″N, 130°13′57″E); KAUM–I. 142212– 142220 , 142227–142241 , 24 specimens, 28.7–52.6 mm SL, collected by R. Koreeda, R. Furuhashi, N. Shimizu & S. Kano, 25 Apr. 2020, gravel beach at Tsuchikawa, Ichiki-kushikino (31°46′49″N, 130°10′48″E). Osumi Peninsula (Kagoshima Pref.): KAUM–I. 149613 , 33.6 mm SL, collected by R. Koreeda, 13 Feb. 2021, gravel beach near Furusato River mouth, Sata , Minami-osumi , Kimotsuki-gun (31°02′52″N, 130°43′41″E). Tanega-shima island (Kagoshima Pref.): KAUM–I. 146245 , 26.2 mm SL, collected by R. Furuhashi, 18 Sept. 2020, gravel beach on east coast of Kumano Fishing Port , Nakatane, Kumage-gun (30°27′48″N, 130°58′08″E) .

Diagnosis. A species of Luciogobius with the following combination of characters: total second dorsal-fin rays 10–13 (modally 11); total anal-fin rays 12–15 (usually 13 or 14); pectoral-fin rays 10–16 (usually 13–15); vertebrae 16–18 + 23–25 = 40–42 (modally 17 + 24 = 41); P-V 21·22, 22, 22·23, 23, 23·24, 24 and usually 22, 22·23, 23, 23·24; anteriormost anal-fin pterygiophore inserted behind 19–21st (modally 20th) vertebrae; uppermost 2–4 (usually 2–3) rays free on pectoral fin; more than 7 (usually more than 10) pectoral-fin rays branched (uppermost free rays and sometimes lowermost ray unbranched); AAA longer than half body depth at anus to anal-fin origin; dorsal-fin origin just above or behind anterior 1/3 of anal-fin base; pectoral-fin membrane not significantly concave between rays; pelvic fins united, forming a ventral disc; head length 14.2–20.4% of SL; P 2 A length 28.6–33.2% of SL; pre-pelvic-fin length 15.7–21.3% of SL; pre-dorsal-fin length 64.5–71.1% of SL; pre-anal-fin length 59.4– 66.2% of SL; pelvic-fin length 3.6–5.6% of SLand 5.3–7.7% of pre-dorsal-fin length; fresh specimens with bright yellow to green body; post-flexion larvae with narrow and black lateral midline posteriorly on body.

Distribution. Currently known from Korea and Japan ( Fig. 6 ). In Japanese waters, the species has been recorded from Aomori Prefect (Aizawa, 1997; Yamada et al., 2009), Pacific coasts of Honshu to Kyushu [Shizuoka Pref. ( Arai, 1981; Shibukawa et al., 2019), Wakayama Pref. ( Yamada et al., 2009; Hirashima, 2018), Kochi Pref. ( Hirata et al., 1996), Miyazaki Pref. ( Koreeda et al., 2023), and Kagoshima Pref. (this study)], Seto Inland Sea [Osaka Pref. ( Shibukawa et al., 2019), Hiroshima Pref. (Imnoshima island: Yoshigo & Yoshigo, 2018), Yamaguchi Pref. (Naga-shima island: Yamada et al., 2009), and Ehime Prefect ( Takagi et al., 2010; Tsuji, 2013)], Japan Sea and East China Sea coasts of Honshu to Kyushu [Shimane Pref. (mainland and Oki Island: Yamada et al., 2009), Nagasaki Pref. (mainland, Fukue-jima and Tsushima islands: Shiogaki & Dotsu, 1976, 1977; Aizawa, 2006; Yamada et al., 2009), and Kagoshima Prefect (mainland: Tashiro et al., 2022; this study], Kagoshima Bay ( Koreeda et al., 2020), and Osumi Islands (Tanega-shima island: Motomura, 2023).

In southern Kyushu, L. platycephalus is a common species in gravel beaches of Ichiki-kushikino City and on the northwestern coast of Kagoshima Bay (Shirahama beach, Aira City), Kagoshima Prefecture and southern parts of Miyazaki Prefecture, whereas occurrences are very rare (usually only juveniles) in more southern areas. The southern limit of the species appears to be Tanega-shima island ( Fig. 5 ), with L. griseus n. sp. replacing the former on the neighboring island of Yaku-shima. Motomura & Matsunuma (2022) reported that fish faunas differed between Tanega-shima and Yaku-shima, both included in the Osumi Islands; the former being the southernmost distribution limit for many temperate marine fishes, and the latter having a fish fauna similar to that of subtropical western Pacific regions. The boundary between the above fish faunas, known as the Osumi Line ( Fig. 6 ), is believed to be due to the position of the islands relative to the course of the Kuroshio Current, which transports planktonic larvae of tropical/subtropical fishes from lower latitudes ( Motomura & Matsunuma, 2022). The allopatric distribution of L. platycephalus and L. griseus n. sp. appears to be linked to this biogeographical boundary.

Remarks. The P 2 A length of the holotype was not measured in this study, but other morphometrics of the holotype fell within the ranges seen in other material of L. platycephalus .

Luciogobius platycephalus sensu Motomura et al. (2010) was re-identified as L. guttatus by Shibukawa et al. (2019). Luciogobius platycephalus sensu Jin et al. (2013) was not included in the clade of L. platycephalus (this study), suggesting that it was misidentified. Although Shibukawa et al. (2019) included Okinawa-jima island in the distribution of L. platycephalus (without comment), the currently recognized distribution of the latter (temperate regions only), suggests that the Okinawa-jima island record was applicable to L. griseus n. sp..

Figures

FIGURE 5. Habitats of Luciogobius griseus n. sp. A: Rocky coast of Ambo, Yaku-shima island (red arrow: pool formed by freshwater spring in intertidal zone); B and F: coast around Zatsun River mouth, Okinawa-jima island; C: rocky coast of Imazato, Amami-oshima island (red arrow: freshwater spring in intertidal zone); D: gravel beach of Akirigami, Tokuno-shima island; E: Otoko River mouth, Yaku-shima island.

FIGURE 6. Distribution of species of the Luciogobius platycephalus complex. Stars: L. griseus; circles: L. platycephalus; triangles: Luciogobius sp. 7 sensu Shibukawa et al. (2019). Purple dotted line indicates Osumi line.

FIGURE 9. Fresh specimens of Luciogobius platycephalus from Kagoshima Bay (A: KAUM–I. 153354, male, 51.6 mm SL), western coast of Kyushu (B: KAUM–I. 142212, female, 51.5 mm SL; C: KAUM–I. 142238, female, 30.6 mm SL), southeastern coast of Kyushu (D: KAUM–I. 149613, female, 33.6 mm SL), and Tanega-shima island (E: KAUM–I. 146245, female, 26.2 mm SL). Photographs taken immediately after fixation.

Tables

TABLE 2. Frequency distribution of meristic counts of the Luciogobius platycephalus complex (this study only).

			Dorsal-fin rays						Anal-fin rays
	9	10	11	12	13		7	...	11	12	13	14	15
L. griseus n. sp. L. platycephalus Luciogobius sp. 7	1	10 13 1	27 47 2	5 18 7	1		1			4 4	24 31 4	14 39 4	5 2
			Pectoral-fin rays						Abdominal vertebrae				Caudal vertebrae
	10	11	12	13	14	15	16		16	17	18		23	24	25
L. griseus n. sp. L. platycephalus Luciogobius sp. 7	1		3 5	23 17 3	11 32 3	5 22 4	2 1		3	13 59 4	26 6		25 6	12 54 2	8 2
	Total vertebrae						P-V								APB*
	40	41	42		21·22	22	22·23 23		23·24	24	24·25		19	20	21	…	24
L. griseus n. sp. L. platycephalus Luciogobius sp. 7	5 4	32 55 2	2 9 2		1	11	1 24	3 17 2	9 11	10 1 1	11 1		1 8	9 37 2	21 3 1		1