Luciogobius griseus, Koreeda & Maeda & Motomura, 2023

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 : 392-400

publication ID	https://doi.org/ 10.11646/zootaxa.5361.3.5
publication LSID	lsid:zoobank.org:pub:AFEFD8C9-ABC1-4793-8B83-49FB7B526389
DOI	https://doi.org/10.5281/zenodo.10166562
persistent identifier	https://treatment.plazi.org/id/03EC5C3E-1C45-0C79-FF7B-FECEFD91FA54
treatment provided by	Plazi
scientific name	Luciogobius griseus
status	sp. nov.

Treatment

Luciogobius griseus n. sp.

[New English name: Dark Spear Earthworm Goby; new standard Japanese name: Sumizome-yari-mimizuhaze]

Figures 1– 3 View FIGURE 1 View FIGURE 2 View FIGURE 3 , 5E, F View FIGURE 5 ; Tables 1–2 View TABLE 1 View TABLE 2

Luciogobius sp. 2 : Maeda et al., 2008: 166, fig. 2a, b (Aritsu Beach, Okinawa-jima island , Okinawa Islands, Okinawa Pref., Japan).

Luciogobius platycephalus View in CoL B: Yamada et al., 2009: 6 (Imazato, Amami-oshima island , Amami Islands, Kagoshima Pref., Japan; Zatsun, Okinawa-jima island, Okinawa Islands, Okinawa Pref., Japan).

Luciogobius sp. 1 : Maeda, 2014: 1249 (referred to Maeda et al., 2008).

Holotype. KAUM–I. 144559 , male, 38.8 mm SL, rocky coast of Imazato (28°19′40″N, 129°17′01″E), Yamato , Oshima-gun , Amami-oshima island , Amami Islands , Kagoshima Pref., Japan (one of the collection sites of Luciogobius platycephalus B sensu Yamada et al., 2009), collected by R. Koreeda, R. Furuhashi & T. Akaike, 21 July 2020. GoogleMaps

Paratypes. 39 specimens (14.7–42.3 mm SL) from Japan. Yaku-shima island (Osumi Islands), Kagoshima Pref.: BMNH 2023.7.19.1 female, 33.1 mm SL, KAUM–I. 163085 , male, 39.7 mm SL, KAUM–I. 163086 , female, 35.2 mm SL, KAUM–I. 163087 , female, 34.4 mm SL, KAUM–I. 163088 , female, 33.9 mm SL, KAUM–I. 163090 , female, 29.4 mm SL, KAUM–I. 163091 , female, 28.9 mm SL, KAUM–I. 163250 , male, 38.6 mm SL, KAUM–I. 163251 , female, 36.4 mm SL, KAUM–I. 163253 , female, 34.3 mm SL, KAUM–I. 163254 , male, 34.2 mm SL, KAUM–I. 163255 , female, 31.0 mm SL, KAUM–I. 163256 , male, 28.6 mm SL, KAUM–I. 163257 , female, 27.3 mm SL, Otoko River mouth, Koseda, Yakushima-cho , Kumage , collected by R. Koreeda, R. Furuhashi & D. Kato, 4 Dec. 2021 ; KAUM–I. 163183 , female, 42.3 mm SL, GoogleMaps KAUM–I. 163184 , male, 39.6 mm SL, GoogleMaps KAUM–I. 163185 , female, 38.1 mm SL, GoogleMaps KAUM–I. 163186 , female, 36.4 mm SL, GoogleMaps KAUM–I. 163187 , female, 32.9 mm SL, rocky coast of Ambo (30°19′14″N, 130°39′40″E), Yakushima-cho, Kumage , collected by R. Koreeda & R. Furuhashi, 3 Dec. 2021 GoogleMaps . Amami-oshima island (Amami Islands), Kagoshima Pref.: KAUM–I. 144560 , female, 37.0 mm SL, same as holotype; GoogleMaps KAUM–I. 144658 , male, 21.8 mm SL, sandy beach on south of Heda River mouth (28°15′13″N, 129°12′28″E), Heda, Uken , Oshima , collected by R. Koreeda, 23 July 2020 GoogleMaps ; KAUM–I. 144656 , sex unknown, 27.6 mm SL, Honohoshi Beach (28°07′45″N, 129°12′29″E), Sogari, Setouchi, Oshima , collected by N. Shimizu, 24 July 2020 GoogleMaps . Tokuno-shima island ( Amami Islands ), Kagoshima Pref.: ANSP 208665 View Materials , male, 23.0 mm SL, GoogleMaps KAUM–I. 143835 , female, 33.9 mm SL, GoogleMaps KAUM–I. 143836 , female, 31.1 mm SL, GoogleMaps KAUM–I. 143837 , male, 31.4 mm SL, GoogleMaps KAUM–I. 144028 , male, 22.8 mm SL, GoogleMaps KAUM–I. 144029 , male, 21.5 mm SL, GoogleMaps USNM 445731 View Materials , female, 31.9 mm SL, south of Akirigami River mouth (27°45′49″N, 128°54′25″E), collected by R. Koreeda & R. Furuhashi, 2–3 July 2020 GoogleMaps . Okinawa-jima island ( Okinawa Islands ), Okinawa Pref.: AMS I. 51113-001 , female, 34.7 mm SL, KAUM–I. 154202 , female, 38.4 mm SL, KAUM–I. 154203 , female, 39.7 mm SL, KAUM–I. 154204 , female, 39.0 mm SL, KAUM–I. 154205 , 35.4 mm SL, Zatsun River mouth, Kunigami-son, collected by R. Koreeda, R. Furuhashi, T. Akaike & N. Shimizu, 13 Mar. 2021 ; KAUM–I. 180992 , female, 20.6 mm SL, KAUM–I. 180993 , sex unknown, 21.7 mm SL, KAUM–I. 180994 , sex unknown, 14.7 mm SL, KAUM–I. 180996 , male, 21.5 mm SL, Aritsu coast, Nago , collected by K. Maeda & N. Ogata, 19 Apr. 2008 ; KAUM–I. 182433 , sex unknown, 16.3 mm SL, Aritsu coast, Nago , collected by R. Furuhashi, 9 Apr. 2023 .

Non-type specimens. 2 specimens (13.8–26.6 mm SL) from Okinawa-jima island, Japan. KAUM–I. 180991 , female, 26.6 mm SL, Aritsu River mouth, Nago , collected by K. Maeda & N. Ogata, seine net, 15 Mar. 2008 (collected as postflexion larva and maintained in aquarium until fixation on 17 Mar. 2009) ; KAUM–I. 182447 , postflexion larva, 13.8 mm SL, Aritsu River mouth, Nago , collected by K. Maeda, R. Furuhashi & R. Koreeda, seine net, 9 Apr. 2023 .

Diagnosis. The new species is distinguished from all congeners by the following combination of characters: total second dorsal-fin rays 9–12 (modally 11); total anal-fin rays usually 12–14 (modally 13); pectoral-fin rays 12–15 (modally 13); vertebrae 17 or 18 + 23 or 24 = 40–42 (usually 18 + 23 = 41); P-V 22·23, 23, 23·24, 24, 24·25 (usually 23·24, 24, 24·25); anteriormost anal-fin pterygiophore inserted behind 19–24th (usually 19–21st, modally 21st) vertebrae; uppermost 2–4 (modally 2–3) rays free on pectoral fin; 8–12 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 13.9–20.8% of SL; P 2 A length 32.0–36.4% of SL; pre-pelvic-fin length 14.4–22.1% of SL; pre-dorsal-fin length 68.9–72.9% of SL; pre-anal-fin length 63.5– 67.7% of SL; pelvic-fin length 2.8–4.7% of SL and 4.0–6.5% of pre-dorsal-fin length; greenish dark brown body when fresh; post-flexion larvae lacking black lateral midline posteriorly on body.

TABLE 1. (Continued)

Description. Data for holotype (mature male) is presented first, followed by paratypes and non-type specimens data in parentheses (if different). Counts and measurements are given in Tables 1 View TABLE 1 and 2 View TABLE 2 . Body elongate, compressed posteriorly. Head strongly depressed. Eyes small (sometimes unequally-sized), rounded, covered with thin skin (sometimes deeply embedded after fixation), located anterodorsally on head; dorsal and posterior surface of skin covering eyes rounded, not projecting posteriorly. Interorbital space wide (relatively narrow in females and young males), shorter than snout, with a transverse ridge anteriorly (rarely completely flat). Anterior nostril with short tube, anterior tip reaching to upper lip, base located just behind maxilla; posterior nostril rounded, located in front of eye. Dorsal profile of snout slightly swollen dorsally, especially above nostril. Posterior dorsum of head between eye and nape relatively strongly swollen, concave centrally in dorsal view (less swollen in females and young males). Single low longitudinal ridge extending from below anterior nostril to behind eye ( Fig. 2 View FIGURE 2 ). Lateral outline of head from nostril to behind eye slightly concave (females and young males relatively strongly concave: Figs. 1B View FIGURE 1 , 2 View FIGURE 2 ). Mouth oblique; posterior end of maxilla extending beyond vertical through eye. Pair of symphysial flaps fused anteriorly, tip rounded. Jaws with bands of 4–6 rows of small conical teeth. Tongue free, anteriorly bilobed. Gill opening narrow, extending below upper end of pectoral-fin base to between posterior end of preopercle and pectoral-fin base. Anus located behind midpoint of body. Urogenital papilla just behind anus, small and rounded or short longitudinally ellipsoid (relatively long longitudinally ellipsoid with ventral slit in females, sometimes unclear in young individuals of both sexes).

Second dorsal fin relatively small; origin posterior to anus; distal margin weakly elevated, rounded; posteriormost rays branched at base, posterior branch shorter than anterior branch; posterior margin lacking serrations. Anal fin relatively small and low; origin slightly behind midpoint between anus and dorsal-fin origin, distance between anus and anal-fin origin greater than half body depth at anus to anal-fin origin; distal margin of anal fin weakly convex; posteriormost rays branched basally, posterior branch shorter than anterior branch; posterior margin lacking serrations. Pectoral fin small; uppermost 2 rays (uppermost 2–4 rays and sometimes lowermost single ray) free (free rays absent in post-flexion larvae); free rays unbranched, other rays branched; posterior margin of fin membrane between each ray weakly concave, except for free rays; all rays lacking serrations. Paired sucker-shaped pelvic fins small, fused, frenum with smooth margin. Caudal fin rounded (truncated in post-flexion larvae).

Cephalic sensory system: Canals and pores absent. Cephalic sensory papillae shown in Fig. 2 View FIGURE 2 .

Coloration of live and fresh specimens: In juveniles and adults ( Fig. 1 View FIGURE 1 ), body slightly greenish- brown, except white ventrally from head to anal-fin origin (ventral part of trunk yellow to orange, eggs visible through semitransparent muscle tissue on ventral surface in mature females). Iris golden. Pupil black. In life, body sometimes pale gray or slightly blueish or purplish. Larval stage coloration given in Maeda et al. (2008); photographs of anesthetized post-flexion larva shown in Fig. 3 View FIGURE 3 .

Coloration of preserved specimens. Body brown dorsally, pale yellowish-brown ventrally.

Sexual dimorphism. Sexual dimorphism observed in adult males are as follows: posterior dorsum of head strongly swollen ( Figs. 1 View FIGURE 1 , 2 View FIGURE 2 ); interorbital space relatively long ( Figs. 1 View FIGURE 1 , 4 View FIGURE 4 ); urogenital papilla small rounded or short longitudinally ellipsoid (long longitudinally ellipsoid with a ventral slit in females).

Swelling of the head in males is generally common Luciogobius , including the Luciogobius platycephalus complex ( Shiogaki & Dotsu, 1976, 1977). However, a difference in interorbital width between sexes is known in only one species to date, L. parvulus ( Snyder, 1909) ( Shiogaki & Dotsu, 1971: as Expedio parvulus ), although it is common in species of the L. platycephalus complex (this study: Figs. 1 View FIGURE 1 , 3 View FIGURE 3 , 10 View FIGURE 10 , 11). Urogenital papilla shape is closely similar to that of L. platycephalus (see Shiogaki & Dotsu, 1976).

Etymology. The specific name griseus refers to the gray dorsal body color in living specimens ( Fig. 5E, F View FIGURE 5 ).

Distributional and ecological notes. Currently known from subtropical areas of Japan, only in the Nansei Islands ( Maeda et al., 2008; Yamada et al., 2009; Maeda, 2014; this study: Fig. 6 View FIGURE 6 ): Yaku-shima, Amami-oshima, Tokuno-shima, and Okinawa-jima islands.

Except on Tokuno-shima ( Fig. 5D View FIGURE 5 ) and Honohoshi Beach (Amami-oshima), all adult specimens were collected at low tide from just under rocky gravel or at depths of 5–10 cm in intertidal sediment subjected to freshwater runoff from springs or rivers ( Fig. 5A–C, E–F View FIGURE 5 ). At Tokuno-shima and Honohoshi Beach sites, only a few small individuals were found, 20–30 cm deep in deposited gravels. Larger individuals were found only in coastal areas influenced by river mouths or freshwater springs, in this study. Such habitats were strongly influenced by freshwater flowing through gravel or sediment interstitial spaces ( Fig. 5A, C, E, F View FIGURE 5 ). At the Zatsun River, no individuals were observed when the river mouth was completely closed and freshwater inflow to the adjacent gravel area restricted ( Fig. 5B View FIGURE 5 ; 10 View FIGURE 10 Apr. 2023), whereas many had been observed when the river mouth was open, releasing considerable freshwater to the gravel deposits ( Fig. 5E View FIGURE 5 ; 13 Mar. 2021). The species may inhabit deep underground-gravel layers or the hyporheic zone of brackishwater areas, moving to surface-gravel layers as the freshwater input increases.

Maeda et al. (2008) documented the collection of larvae belonging to the species at Aritsu Beach, situated in close proximity to the entrance of the Aritsu River on Okinawa-jima island. This collection period extended from January to April, with the larvae estimated to be between 34 and 36 days old. In the present study, ripe females were collected on Yaku-shima island in December 2021.

Comparisons. Luciogobius griseus n. sp. belongs to the L. platycephalus complex, characterized by dorsal-fin rays fewer than 13; total vertebrae 40–42; dorsal-fin origin posterior to anal-fin origin; pectoral fin with more than two free rays; distance between anus to anal-fin origin greater than half body depth at anus; and first anal-fin pterygiophore inserted between second and fourth haemal spines.

The Luciogobius platycephalus complex comprises three species, L. griseus n. sp., L. platycephalus , and Luciogobius sp. 7 sensu Shibukawa et al. (2019), all of which share similar meristic counts ( Table 2 View TABLE 2 ). Although Luciogobius griseus n. sp. is very similar to L. platycephalus , the former has greater pre-dorsal-fin length (68.9– 72.9% of SL vs. 64.5–71.1%; Fig. 8C View FIGURE 8 ) and P 2 A length (32.0–36.4% of SL vs. 28.6–33.2%; Fig. 8B View FIGURE 8 ). In fact, the combination of these two characters further differentiates the two species (pre-dorsal-fin length + P 2 A length 103.0– 107.3% of SL vs. 95.4–101.6%; Fig. 7B View FIGURE 7 ). In addition, L. griseus n. sp. differs from L. platycephalus in having P-V 22·23, 23, 23·24, 24, or 24·25 (usually 23·24, 24, or 24·25) vs. P-V 21·22, 22, 22·23, 23, 23·24, or 24 (usually 22, 22·23, 23, or 23·24) in L. platycephalus ( Table 2 View TABLE 2 ); anteriormost anal-fin pterygiophore usually inserted behind 21st vertebrae in L. griseus vs. 20th in L. platycephalus ( Table 2 View TABLE 2 ); shorter head length than in the same size class of L. platycephalus ( Fig. 8A View FIGURE 8 ); longer pre-anal-fin length, usually 63.5–67.7% of SL vs. 59.4–65.3% ( Fig. 8D View FIGURE 8 ); shorter pre-pelvic-fin length 14.4–22.1% of SL vs. 15.3–21.3% ( Fig. 8E View FIGURE 8 ); shorter pelvic-fin length 2.8–4.7% of SL vs. 3.5–5.6% ( Fig. 8F View FIGURE 8 ), and 4.0–6.5% of pre-dorsal-fin length vs. 5.3–7.8% ( Fig. 7A View FIGURE 7 ); and body relatively darker, greenish-brown vs. usually light green to yellowish-green body, except adults> 50 mm SL ( Figs. 1 View FIGURE 1 , 9 View FIGURE 9 ). Luciogobius griseus n. sp. is also slightly slender than L. platycephalus , with body depth at pelvic-fin origin 5.2–7.1% of SL vs. 5.5–8.8%. Morphometrics are important characters to separate L. griseus n. sp. from L. platycephalus , but changes associated with growth should be considered when using these characters to distinguish between the two species.

Luciogobius griseus n. sp. is also similar to Luciogobius sp. 7 sensu Shibukawa et al. (2019) in having a relatively darker body. However, the pectoral-fin membrane is less incised in L. griseus n. sp. (strongly incised in Luciogobius sp. 7 ), with more branched pectoral-fin rays [8–12 vs. 0–8 (usually fewer than 6, and 0, respectively, in specimens <38.0 mm SL)].

Post-flexion larvae of L. griseus n. sp. lack a black lateral midline posteriorly on the body ( Maeda et al., 2008: fig. 2; this study: Fig. 3B View FIGURE 3 ), such being present in L. platycephalus ( Shiogaki & Dotsu, 1977) . The larval stage of Luciogobius sp. 7 is unknown.

Remarks. KAUM–I. 163183 (42.3 mm SL) had a longer pre-anal-fin length (73.0% of SL: Fig. 8D View FIGURE 8 ) than other specimens (63.5–67.7%), with the anteriormost anal-fin pterygiophore inserted behind the haemal spine of the 24th vertebrae (usually 19th to 21st). The specimen was regarded as a deformed individual due to lacking the anterior part of the anal-fin rays (including spines: anal-fin rays 7) and associated pterygiophores.

Yamada et al. (2009) reported two clades of L. platycephalus ( L. platycephalus A from Honshu, Kyushu, and surrounding islands; L. platycephalus B from Amami-oshima and Okinawa-jima) in their phylogenetic tree based on the mitochondrial cytochrome b gene and six protein-coding nuclear genes. Given the designated localities, it is probable that the former and latter clades correspond to L. platycephalus and and the new species described herein. Several specimens of L. griseus n. sp. examined in this study (including the holotype) were collected from Imazato (Amami-oshima) and Zatsun (Okinawa-jima), the same location in which Yamada et al. (2009) collected L. platycephalus B for their study.