Luciogobius sp. 7 sensu Shibukawa et al. (2019)

[Standard Japanese name: Hauchiwa-yari-mimizuhaze]

Figure 10; Table 2

Luciogobius sp. 7: Shibukawa et al, 2019: 67, figs. 19B, 20E–G, 21C (Shizuoka Pref., Japan).

Examined specimens. 10 specimens (33.9–65.9 mm SL) from Japan. Shizuoka Prefecture: KAUM –I. 139315, 43.1 mm SL, collected by R. Yamashita. KAUM –I. 157744–157747, 4 specimens, 33.9–65.9 mm SL, collected by H. Saito, 10 June 2021, KAUM –I. 165340, 49.3 mm SL, KAUM – I. 165341, 41.8 mm SL, collected by K. Mochizuki, 2 Jan. 2022, Yaizu. Kochi Prefecture: KAUM –I. 159028, 32.1 mm SL, KAUM – I. 159029, 33.2 mm SL, collected by H. Saito, 13 July 2021, Niyodo River mouth, Haruno. KAUM – I. 159033, 51.3 mm SL, collected by H. Saito, 22 July 2021, Shinjo River mouth, Suzaki .

Morphological characters of examined specimens. Total second dorsal-fin rays 10–12 (modally 12); total anal-fin rays 13–15 (usually 13 or 14); pectoral-fin rays 13–16; vertebrae 17 + 24–25 = 41 or 42; uppermost 2–4 rays free on pectoral fin; fewer than 5 pectoral-fin rays branched (central rays branched in specimens> 50 mm SL); 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 strongly concave anteriorly; pelvic fins united.

Distribution. Currently known from Japan [Shizuoka, Wakayama and Kochi prefectures (Shibukawa et al., 2019; Maeda & Hirashima, 2021; Okumura et al., 2023)]. The species prefers gravel deposits on beaches, rather than rocky coasts (Shibukawa et al., 2019).

Remarks. The pre-dorsal fin length + P 2 A length of 98.4–102.1% of SL in Luciogobius sp. 7 sensu Shibukawa et al. (2019) is similar to that of L. platycephalus, but shorter than in L. griseus n. sp. (Fig. 7).

Three individuals from Kochi Prefecture had relatively shorter pelvic-fin length (3.0–3.2 % of SL vs. 3.1–4.0% of SL) than in Shizuoka specimens (Fig. 8F), although specimens from both areas shared fewer than 8 branched pectoral-fin rays, a diagnostic character of the species according to Shibukawa et al. (2019). The latter reported also that branched rays were absent in individuals <38.0 mm SL.

Key to species of the Luciogobius platycephalus complex (except larvae and juveniles): each body proportion needs to be aware of changing with growth (see Figs. 7, 8)

1a. Pectoral fin with 7–13 branched rays (usually more than 10); posterior margin of pectoral-fin membrane not strongly concave (except for free rays).................................................................................. 2

1b. Pectoral fin with 0–8 branched rays (usually 6; 0 in specimens <38 mm in SL); posterior margin of pectoral-fin membrane strongly concave; occurs in accreting beach......................................................................................... Luciogobius sp. 7 sensu Shibukawa et al. (2019) (Japanese name: Hauchiwa-yari-mimizuhaze)

2a. Pre-dorsal-fin length <70% of SL (except in a specimen 26.1 mm SL); pelvic-fin length> 5.3% of pre-dorsal-fin length in specimens 32 mm SL or larger (> 5.9% in smaller specimens); pre-dorsal-fin length + P 2 A length 95.4–101.6% of SL; bright yellow to green body in live and fresh specimens (except individuals> 50 mm SL); usually occurs along temperate rocky coasts in Japan (Aomori Pref. to Tanega-shima island) and Korea ….............. Luciogobius platycephalus (Yari-mimizuhaze)

2b. Pre-dorsal-fin length> 69.5% of SL; pelvic-fin length <5.3% of pre-dorsal-fin length in specimens 32 mm SL or larger (<6.0% in smaller specimens); pre-dorsal-fin length + P 2 A length 103.0–107.3% of SL; gray in life (sometimes bluish or purplish), greenish dark brown when fresh; usually occurs near subtropical river mouths or coastal freshwater springs in Japan (Yaku-shima island to Okinawa-jima island)......................... Luciogobius griseus n. sp. (Sumizome-yari-mimizuhaze)