Obliquogobius yamadai Shibukawa & Aonuma, 2007

Su, Yo, Hsu, Yu-Chieh & Ho, Hsuan-Ching, 2025, New records of two goby species from Taiwan, northwestern Pacific Ocean (Gobiiformes: Gobiidae), Zootaxa 5693 (1), pp. 66-78 : 72-75

Obliquogobius yamadai Shibukawa & Aonuma, 2007

English name: Yamada’s deep-dwelling goby

New Chinese name: ƜHKÑṞẊ

Figs. 4 , 5 . Tables 3 , 4 .

Obliquogobius yamadai Shibukawa & Aonuma, 2007:147 (Type locality: East China Sea, 31°28'48''N, 127°00'54''E, depth 133 meters. Holotype: NSMT-P73003): Chen et al. 2012: 269 (in key). Matsui et al. 2014: 8 (listed, Wakasa Bay, Japan). Sonoyama et al. 2020: 106 (listed, Yamaguchi Prefecture, Japan). Fujiwara et al. 2021: 547 (compared to the new species described). Ho et al. 2021: 500, plate 8C (listed, South Java, Indonesia). Fricke 2022: 7 (in key). Gloerfelt-Tarp & Kailola 2022:257 (southern Indonesia and northwestern Australia)

Specimens examined

NMMB-P 41620 , 41.4 mm SL, male, off Dong-gang fishing port ( ca. 22°22'22"N, 120°27'34"E), Pingtung, southwestern Taiwan, 9 January 2025, collected by Y. Su et al.

Description of Taiwanese specimens. Meristic and morphometric data are provided in Tables 3 and 4 .

Dorsal-fin rays VI–I, 9; pectoral-fin rays 22/22; pelvic-fin rays I, 5/I, 5; anal-fin rays I, 9; principal caudal-fin rays 8+7. Gill rakers on outer face of first arch 2+1+10=13. Longitudinal scale rows 24; transverse scale rows from anal-fin origin dorsoanterior to first dorsal-fin base 6; transverse scale rows from anal-fin origin dorsoposterior to second dorsal-fin base 7; transverse scale rows from second dorsal-fin origin ventroposterior to anal-fin base 8; circumpeduncular scales 12; predorsal scales 0. Vertebrae 10+16=26; dorsal-fin interdigitation pattern 3/22110/9; anal-fin pterygiophores anterior to first haemal spine 2.

Body robust, greatest depth at second dorsal-fin origin, depth 3.5 in SL. Head oval in shape, length 3.5 in SL, its depth smaller than its length, depth 1.6 in HL; upper profile in front of dorsal fin slightly rounded; eyes large, 2.3 in HL; space between eyes narrow, interorbital width 35.6 in HL; snout slightly rounded, its length 4.7 in HL and not protruding before premaxilla.

Mouth moderate, upper-jaw length 2.3 in HL; its posterior end anterior to vertical through middle of eye. Two nostrils, with anterior nostril forming short tube and situated at horizontal through middle of eye; posterior nostril forming pore, immediately in front of eye and situated higher than anterior nostril. Premaxilla and dentary covered with canine teeth, with outermost row enlarged and recurved. Vomer and palatine edentate.

Gill rakers on first arch rod-shaped and laterally compressed; rakers on outer face of second to fourth arches and on inner face of outer three arches forming bumps. Pseudobranchial filaments present and short, their number undetectable. Gill membrane connected to isthmus anteriorly; gill opening extending anteriorly, reaching slightly before vertical through posterior margin of preopercle.

Body scales deciduous, covering body, upper operculum, and pectoral and caudal-fin bases. Nape naked. Head sensory pores and papillae shown in Fig. 5 . Sensory canal well developed, including pores B’, C, D, E, F, G, H’, M’, N and O’; all pores paired except for C and D. Sensory papillae on head well developed: row a and c with 3 papillae aligned in nearly horizontally; row cp with 1 papilla, situated just below posterior most papillae of row c; row d with 7 papillae; row f with 2 papillae just after symphysis of lower jaw; row ot with 11 papillae; and row z with 3 papillae aligned vertically.

Dorsal-fin spines flexible, with first spine longest and filamentous; all soft rays branched. Pectoral fin rounded, slightly pointed; length 3.5 in SL, its tip reaching beyond vertical through anal-fin origin. Pelvic fin long, its length 4.3 in SL; its tip reaching anus when adpressed; fifth rays connected via membrane; pelvic fin united anteriorly but without frenum. Anal-fin soft rays progressively longer posteriorly. Caudal fin pointed, length 2.6 in SL. Caudal-peduncle somewhat stout, length and depth 1.0 and 2.6 in HL, respectively.

Coloration

When fresh ( Fig. 4A, B ), body dusky, with eight transverse yellow bars from nape to caudal-fin base. Head dusky and slightly darker than body. Sclera and nape behind eye slightly yellow. First dorsal fin dusky, becoming darker to black distally; second dorsal-fin, anal, pectoral-fin rays dusky; caudal-fin rays with yellow bars but faded and turned dusky subsequently (YS and YCH, pers. obs.), with its tips black; membranes of second dorsal and caudal fins pale, or with very scare black pigments; second to fifth pelvic-fin soft rays dark to black, with its membranes with dense black pigments. Caudal-fin base with rounded patch of dense black pigments.

When preserved ( Fig. 4C ), coloration similar to that of fresh, with yellow region turned pale. Oral cavity, inner operculum, and gill rakers and arches pale. Caudal peduncle with one thin black line ventrally, originates from end of anal-fin base to near procurrent caudal-fin rays.

Distribution

Originally described from the East China Sea and Japan, with possible records from the Philippines and from regions between southern Indonesia and northwestern Australia (Gloerfelt-Trap & Kailola 1984; Shibukawa & Aonima 2007). The latter record from southern Indonesia and northwestern Australia was confirmed by Gloerfelt-Trap & Kailola (2022). Our specimen represent the first record of the genus Obliquogobius from Taiwan and fills the distribution gap of this species between Japan and southern Indonesia and northwestern Australia. Inhabits at depths down to 165 m (Shibukawa & Aonima 2007). Our specimens were collected at depth ca. 100– 300 m.

Remarks

The present specimen is identified as Obliquogobius yamadai based on the combination of second dorsal-fin ray I, 9; pore G of anterior oculoscapular canal present; anterior end of gill opening reaching slightly before posterior margin of preopercle; lateral side of nape, pectoral-fin base, and cheek with scales; midline of nape naked; head length 28.4% SL; caudal-fin length 38.8% SL, with its upper lobe longer than lower lobe; first dorsal fin without a black spot; eight transverse yellow bars from the nape to caudal-fin base; and a rounded patch of dense black pigment at the caudal-fin base ( Shibukawa & Aonuma 2007; Chen et al. 2012).

Meristic values closely match those of the type series ( Table 3 ). Several morphometric differences are apparent ( Table 4 ), particularly in caudal-peduncle length (31.4% SL vs. 50.6–57.6% SL in the type series) and the length of the first dorsal-fin spine (26.1% SL vs. 13.0–16.8% SL). The caudal-peduncle discrepancy likely reflects different measurement landmarks; here, it was measured from the end of the anal-fin base to the caudal-fin base, whereas Shibukawa & Aonuma (2007) appear to have measured from either the anal-fin origin or the anus. Additionally, our examination revealed that the first dorsal-fin spine in our specimen is elongated and filamentous, a condition not mentioned in the original description. This character is unlikely to be related to sexual dimorphism, as either sex of type specimens does not have their fin spine elongated ( Shibukawa & Aonuma 2007). Therefore, further specimens are required to determine whether this represents an abnormality or intraspecific variation.

Figures

FIGURE 4. Obliquogobius yamadai Shibukawa & Aonuma, 2007, NMMB-P 41620, 41.4 mm SL. A. Freshly caught B. Fresh, photographed after ca. three hours of keeping fresh. C. Preserved.

FIGURE 5. Line drawing of head pores (yellow) and sensory papillae of Obliquogobius yamadai Shibukawa & Aonuma, 2007, NMMB-P 41620, 41.4 mm SL. A. Dorsal view B. Lateral view C. Ventral view. Anterior to right. FIGURE not to scale. Damaged areas were shaded in gray. Red arrow indicates anterior-most end of gill opening. Abbreviations: AN, anterior nostril; DO, dorsal-fin origin; PN, posterior nostril.