A new subtropical species of goby of the genus Luciogobius (Gobiidae) from southwestern Japan Author Koreeda, Reo 0000-0002-6977-3357 The United Graduate School of Agricultural Sciences, Kagoshima University, 1 - 21 - 24 Korimoto, Kagoshima 890 - 0065, Japan k4920583@kadai.jp Author Maeda, Ken 0000-0003-3631-811X Marine Eco-Evo-Devo Unit, Okinawa Institute of Science and Technology Graduate University, 1919 - 1 Tancha, Onna, Okinawa 904 - 0495, Japan Author Motomura, Hiroyuki 0000-0002-7448-2482 The Kagoshima University Museum, 1 - 21 - 30 Korimoto, Kagoshima 890 - 0065, Japan text Zootaxa 2023 2023-11-02 5361 3 390 408 https://www.mapress.com/zt/article/download/zootaxa.5361.3.5/52197 journal article 10.11646/zootaxa.5361.3.5 1175-5326 10144864 AFEFD8C9-ABC1-4793-8B83-49FB7B526389 Luciogobius griseus n. sp. [New English name: Dark Spear Earthworm Goby; new standard Japanese name: Sumizome-yari-mimizuhaze] Figures 1– 3 , 5E, F ; Tables 1–2 Luciogobius sp. 2 : Maeda et al ., 2008: 166 , fig. 2a, b (Aritsu Beach, Okinawa-jima island , Okinawa Islands, Okinawa Pref. , Japan ). Luciogobius platycephalus 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 . 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, KAUM–I. 163184 , male , 39.6 mm SL, KAUM–I. 163185 , female , 38.1 mm SL, KAUM–I. 163186 , female , 36.4 mm SL, 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 . Amami-oshima island (Amami Islands), Kagoshima Pref. : KAUM–I. 144560 , female , 37.0 mm SL, same as holotype; 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 ; 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 . Tokuno-shima island ( Amami Islands ), Kagoshima Pref. : ANSP 208665 , male , 23.0 mm SL, KAUM–I. 143835 , female, 33.9 mm SL, KAUM–I. 143836 , female , 31.1 mm SL, KAUM–I. 143837 , male , 31.4 mm SL, KAUM–I. 144028 , male , 22.8 mm SL, KAUM–I. 144029 , male , 21.5 mm SL, USNM 445731 , 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 . 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. Counts and proportional measurements of Luciogobius griseus n. sp. .

Holotype	Paratypes
Standard length (SL; mm)	38.8	14.7–42.3
Counts
Total dorsal-fin elements	12	9–12
Total anal-fin elements	13	7–14
Pectoral-fin rays	13	12–15
Pectoral-fin free rays	2	2–5
Pectoral-fin branched rays	10	8–12
Caudal-fin segmented rays	10 + 9	9–12 + 8–10
Pelvic-fin rays	I, 5	I, 5
Vertebrae	17 + 24	17–18 + 23–24 = 40–41
P-V	23·24	22·23, 23, 23·24, 24, 24·25
Measurements (% SL)	r*
Head length (HL)	15.7	13.9–20.8	-0.83
Head depth	6.3	5.2–8.3	0.07
Head width	10.0	7.4–10.0	-0.20
Snout length	4.6	3.5–6.0	-0.49
Upper-jaw length	5.6	4.3–6.3	-0.30
Eye diameter	1.2	1.0–2.2	-0.73
Interorbital width	3.8	2.1–3.7	0.28
Body depth at pelvic-fin origin	5.6	5.2–7.2	-0.11
Body depth at anal	6.3	5.8–8.8	-0.04
Body depth at anal-fin origin	7.2	6.6–9.0	0.03
Body width	6.7	5.0–8.1	-0.08
P2A length	105.9	32.0–36.4	0.63
AAA	10.5	5.2–15.9	0.46
Least caudal-peduncle depth	6.9	6.0–8.4	-0.03
Maximum caudal-peduncle depth	8.8	6.7–9.1	-0.09
Caudal-peduncle length	21.5	19.0–22.9	0.30
Pre-anal length	56.2	54.0–58.3	-0.63
Pre-second dorsal-fin length (PDF)	70.5	68.9–72.9	-0.59
Pre-anal-fin length	66.2	63.1–73.0	-0.37
Pre-pelvic-fin length	16.8	14.4–22.1	-0.76
PDF + P2A length	105.9	103.0–107.3	0.10
Second dorsal-fin base length	11.9	9.3–11.9	-0.04
Anal-fin base length	14.7	7.6–17.1	-0.30
Pectoral-fin length	5.7	5.2–9.2	-0.48

...Continued on the next page TABLE 1. (Continued)

Holotype	Paratypes
Pelvic-fin length	3.0	2.8–4.7	-0.82
Caudal-fin length	10.8	10.8–15.9	-0.69
Measurements (% HL)
Head depth	40.0	32.4–54.3	0.57
Head width	63.6	43.1–63.6	0.54
Snout length	29.5	23.0–29.9	0.24
Upper-jaw length	35.6	28.8–38.3	0.47
Eye diameter	7.5	7.0–13.1	-0.44
Interorbital width	24.1	13.9–23.3	0.70
Measurements (% PDF)
Pelvic-fin length	23.2	15.3–24.9	-0.74

*Pearson’s correlation coefficient. 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 and 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 ). Lateral outline of head from nostril to behind eye slightly concave (females and young males relatively strongly concave: Figs. 1B , 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 . Coloration of live and fresh specimens : In juveniles and adults ( Fig. 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 . 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 , 2 ); interorbital space relatively long ( Figs. 1 , 4 ); urogenital papilla small rounded or short longitudinally ellipsoid (long longitudinally ellipsoid with a ventral slit in females). FIGURE 1. Fresh specimens of Luciogobius griseus n. sp. from Amami-oshima island (A: holotype; KAUM–I. 144559, male, 38.8 mm SL), Yaku-shima island (B: KAUM–I. 163253, female, 34.3 mm SL), Tokuno-shima island (C: KAUM–I. 144049, male, 21.5 mm SL) and live specimens from Yaku-shima island (D: KAUM–I. 163186, female, 36.4 mm SL; E: KAUM–I. 163183, female, 42.3 mm SL). A–C: euthanized before fixation; D, E: living specimens. 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 , 3 , 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 ). 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 ): Yaku-shima, Amami-oshima, Tokuno-shima, and Okinawa-jima islands. FIGURE 2. Head of Luciogobius griseus n. sp. (KAUM–I. 154203), showing cephalic sensory system. Black dots, AN and PN indicate papillae, and points of anterior and posterior nostrils, respectively. FIGURE 3. Fresh specimen of post-flexion larva of Luciogobius griseus n. sp. (KAUM–I. 182447, 13.8 mm SL). Photographs taken before fixation. Except on Tokuno-shima ( Fig. 5D ) 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 ). 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 ). 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 ; 10 Apr. 2023 ), whereas many had been observed when the river mouth was open, releasing considerable freshwater to the gravel deposits ( Fig. 5E ; 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. FIGURE 4. Sexual dimorphism of interorbital space as % of standard length (A) and head length (B) in Luciogobius griseus n. sp. Triangles: males; squares: females; diamonds: sex unknown. 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. 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 ). 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 ) and P 2 A length (32.0–36.4% of SL vs. 28.6–33.2%; Fig. 8B ). 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 ). 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 ); anteriormost anal-fin pterygiophore usually inserted behind 21st vertebrae in L. griseus vs. 20th in L. platycephalus ( Table 2 ); shorter head length than in the same size class of L. platycephalus ( Fig. 8A ); longer pre-anal-fin length, usually 63.5–67.7% of SL vs. 59.4–65.3% ( Fig. 8D ); shorter pre-pelvic-fin length 14.4–22.1% of SL vs. 15.3–21.3% ( Fig. 8E ); shorter pelvic-fin length 2.8–4.7% of SL vs. 3.5–5.6% ( Fig. 8F ), and 4.0–6.5% of pre-dorsal-fin length vs. 5.3–7.8% ( Fig. 7A ); and body relatively darker, greenish-brown vs. usually light green to yellowish-green body, except adults> 50 mm SL ( Figs. 1 , 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. 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. 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 ), such being present in L. platycephalus ( Shiogaki & Dotsu, 1977 ) . The larval stage of Luciogobius sp. 7 is unknown. FIGURE 7. Relationship of (A) pelvic-fin length (P 2 F length) as % of pre-dorsal-fin length (PDF) and (B) PDF + P 2 A length as % of standard length (SL) in the Luciogobius platycephalus complex. Closed star: holotype of L. griseus ; open stars: paratypes of L. griseus ; circles: non-type specimens of L. platycephalus ; triangles: Luciogobius sp. 7 sensu Shibukawa et al . (2019) . Remarks. KAUM–I. 163183 ( 42.3 mm SL) had a longer pre-anal-fin length (73.0% of SL: Fig. 8D ) 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.