Callogobius shunkan Takagi, 1957

(俊Îȇǝȇṯ)

Figures 1–3

Callogobius shunkan Takagi, 1957: 112, Fig. 4 (Holotype: TUFLFB 38063, Matsugaura, Kagoshima Prefecture, Japan)— Delventhal & Mooi, 2013: 156 (comparative material); Akihito et al., 2013: 1397 (key); An et al., 2020: 252 (Jejudo Island, Korea); Goto et al., 2022: 1 (description); Delventhal & Mooi, 2023: 459 (species account).

Callogobius snelliusi (not Koumans, 1953)— Akihito & Meguro, 1977: 119 (description); Akihito, 1984: 264 (species count, Japan).

Materials Examined

NTOUP201506-26, 4, 22.3–48.8 mm SL, locality unknown; coll. I-Shiung Chen et al., 25 Jun. 2015. NTOUP200606-624, 1, 45.5 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. I-Shiung Chen et al., 15 Jun. 2006. NTOUP200710-016, 1, 32.2 mm SL, waters near Chaojing Ocean Park, Zhongzheng District, Keelung City; coll. I-Shiung Chen et al., 31 Jul. 2007. NTOUP200710-021, 1, 30.5 mm SL, waters near Chaojing Ocean Park, Zhongzheng District, Keelung City; coll. I-Shiung Chen et al., 31 Jul. 2007. NTOUP202006-125, 2, 33.0– 33.6 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 3 Jun. 2020. NTOUP202006- 127, 1, 47.5 mm SL, waters near Chaojing Ocean Park, Zhongzheng District, Keelung City; coll. Yu-Yang Shia & Tonisman Harefa, 24 Jun. 2021. NTOUP202007-121, 4, 19.6–41.8 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Hsien-En Li & Tonisman Harefa, 3 Jul. 2020. NTOUP202007-130, 1, 43.8 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 21 Jul. 2020. NTOUP202007-133, 4, 27.0– 40.4 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 23 Jul. 2020. NTOUP202008- 281, 1, 39.9 mm SL, waters near NTOU, Zhongzheng District, Keelung City; coll. Hsien-En Li et al., 21 Aug. 2021. NTOUP202106-389, 1, 38.7 mm SL, waters near NTOU, Zhongzheng District, Keelung City; coll. Hsien-En Li et al., 27 Aug. 2021. NTOUP202106-013, 3, 26.5–47.8 mm SL, Mao’ao Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 7 Jun. 2021. NTOUP202106-022, 1, 37.1 mm SL, Xiaoxianglan, Gongliao District, New Taipei City; coll. Tonisman Harefa & De-Yi Hong, 10 Jun. 2021. NTOUP202107-045, 1, 38.7 mm SL, Mao’ao Bay, Gongliao District, New Taipei City; coll. Tonisman Harefa & De-Yi Hong, 7 Jul. 2021. NTOUP202107-005, 1, 41.6 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Tonisman Harefa & De-Yi Hong, 29 Jul. 2021. NTOUP202107-103, 1, 30.6 mm SL, Dong’ao Bay, Nan’ao Township, Yilan County; coll. Tonisman Harefa & De-Yi Hong, 30 Jul. 2021. NTOUP202108-122, 2, 19.4–36.3 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 5 Aug. 2021. NTOUP202108-129, 4, 30.3–38.4 mm SL, Mao’ao Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 9 Aug. 2021. NTOUP202109-131, 1, 47.3 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 6 Sep. 2021. NTOUP202202-034, 1, 32.6 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 2 Feb. 2022. NTOUP202203-038, 7, 27.9–45.5 mm SL, Longdong Bay, Gongliao District, New Taipei City; coll. Hsien-En Li et al., 2 Feb. 2022.

Diagnosis

D2 I, 9–11; A I, 7–9; P1 16–19; LR 28–32; TR 9–11; Pred 7–9; D-P 4–6.

Three brown blotches present along lateral side of the body (much distinct in juveniles or freshly dead specimens). D1 golden to ochre in colour, marked with about three white oblique wavy stripes. D2 dark ochre with two rows of white oblique spots. Anal fin black, while fades to transparent white at base with a black margin post-mortem.

Descriptions

Morphometric proportions are presented in table 1. Body slightly elongate, cylindrical anteriorly, and laterally compressed toward caudal peduncle. Head slightly depressed; head width greater than depth. Multiple papillose dermal ridges present on the cheek, lower jaw, and operculum, arranged both transversely and longitudinally. Mouth slightly oblique; posterior end of gape not reaching through vertical point of the anterior margin of orbit. Upper lip slightly thicker than lower lip; inner edge of lower lip lined with short, velvety papillae. All teeth conical without specialized forms. Anterior and posterior nostrils both tubular; anterior nostril reaches upper lip when compressed. Genital papillae in males slender and elongate, extending to 1 st anal-fin spine; in females, papilla short, stout, and blunt-ended. Vertebrae counts 10+26=26, P-V=3-22110.

Fins. See table 2 for frequencies of fin element counts. D1 slightly triangular, 1 st and 2 nd spines longest, filamentous elongation of the 2 nd spine occasionally present in mature males; posterior margin slightly curved in some mature individuals. D2 sub-rectangular; posterior soft rays elongated in mature individuals. Anal fin with short base; posterior rays elongated, reaching near posterior margin of caudal peduncle when depressed. P1 slightly ovate, reaching the vertical point of anal fin origin. P2 fused, forming a well-developed disc, posterior tip does not reach anus; connecting membrane and frenum both fully developed.

Squamation. See Table 2 for frequencies of scale counts. Cycloid scales coverage extending posteriorly from the operculum to the first dorsal fin and from abdomen to anus. Mixed patches of cycloid and ctenoid scales present laterally beneath first dorsal fin; from midbody to caudal peduncle, ctenoid scales dominate, bearing numerous fine ctenii. Large cycloid scales with distinctly outlined centre embedded between dermal ridges of cheek, on predorsal region, and ventral side of head, extending anteriorly to vertical point of orbit. Small cycloid scales present from orbit to pectoral base. Fleshy base of pectoral and pelvic fins covered with a few large cycloid scales.

Cephalic sensory organ. See figure 3 for canal pore and papillae row arrangements. Anterior oculoscapular canal bears paired pores σ (anterior orbital margin), and single pores λ and κ (interorbital region), all with short tubular openings (pore λ absent in 5 of 43 specimens). Postorbital portion of anterior oculoscapular canal with paired pores ω and α. Paired pores β and ρ located just above posterior margin of preopercle. Preopercular canal with paired pores γ, δ, and ε, each with short tubular openings. Postorbital canal contains paired pores Θ and τ. Anterior infraorbital and preopercular canals not continuous. All papillae rows located on dermal ridges. Anterior orbital row r divided into r 1 (adjacent to nasal tube) and r 2 (antero-interorbital region), the latter further subdivided into left and right rows. Postorbital row n bilaterally divided. Paired row h not located on a raised ridge and divided into anterior and posterior sections. Cheek rows b and d intersect vertical row 4 below eye, dividing it into 4s (further subdivided into 4s 1 and 4s 2) and 4i. Rows d and e interrupted between rows 1 and 2, forming segments d 1, d 2, e 1, and e 2. Rows z and ot remain unfused. Row i comprises 3 short transverse dermal ridges and a single row of 20–23 papillae. Row f consists of 2 longitudinal rows of papillae symmetrically aligned on anterior lower jaw.

Fresh coloration. See figure 1 for fresh postmortem coloration and figure 2 for underwater in situ coloration. Body overall brown, with abdominal region greyish white. Three prominent triangular brown blotches aligned laterally: one beneath D1 and two beneath D2, each reaching the base of corresponding fin. Head and lips brown, mottled with irregular pale yellow to white blotches. Elevated dermal ridges marked alternately in dark brown and white. Iris with 5 radiating dark brown stripes; orbit encircled by alternating orange-brown and white pigment. D1 ochre with approximately three oblique white stripes or blotches. D2 fin dark yellow to black with white margin and 2 rows of oblique white spots. P1 dark brown with scattered white spots and white margins. P2 dark brown to black; in faded individuals, entire fin becomes white except for a retained black tip. Anal fin black in fresh individuals; faded specimens show white base with black margin. Caudal fin dark brown with white-edged margin and 3–4 transverse rows of white spots extending to mid-fin.

Preserved colorations. All light markings fade to greyish-white. Dark body markings become brownish and may blend with background coloration in specimens not fixed in cold formalin.

Distribution and habitat

Callogobius shunkan was previously recorded from the northwestern Pacific region including coastal areas of Japan and Korea (An et al. 2020; Goto et al. 2022), and its new distribution in Taiwan was exclusively from the northeastern coastal waters not exceeding 15 meters deep. It prefers to inhabit crevices among coral reef rocks in the subtidal zone.

Remarks

Current distribution record of Callogobius shunkan in Taiwan marks the southernmost limit of its known global range, however Sadovy and Cornish (2000) had documented a Callogobius collected from Port Shelter (+尾ª) that closely resembles C. shunkan based on the figures given (pp. 244, unnumbered figure), but the species was identified as C. maculipinnis (Fowler, 1918), examinations upon this collection may confirm the identity of this Callogobius and possibly will extend the distribution of C. shunkan southwards. Among the Callogobius species found in Taiwan, C. shunkan can be distinguished primarily by the sensory papillae row i, which bears only 3 transverse rows of cutaneous ridges (vs.> 10 in other species), it most resembles C. nigromarginatus but can be differentiated from the latter by the 1 st and 2 nd spines of D1 being the longest (vs. 3 rd spine longest), more transverse scale row counts (9–11, modally 10 vs. 7–9, modally 8) and predorsal scale counts (7–9, modally 8 vs. 5–6, modally 5), and the papillose fleshy ridges rows z and ot not fusing (vs. rows z and ot fusing into a single row z+ot).

This species was previously misidentified as the apparently closely related C. snelliusi Koumans, 1953 in Japanese literatures (Akihito & Meguro 1977; Akihito 1984). In the original descriptions of C. shunkan (Takagi 1957), it was differentiated from C. snelliusi by having lower body depth (18% of SL vs. 25% of SL), smaller eye diameter (20% of HL vs. 33% of HL), longer snout (approx. 1.6 times of eye diameter vs. slightly shorter than eye diameter), and differences in fin ray counts (D2 I, 10 vs. I, 8; A I, 8 vs. I, 6). Akihito et al. (2013), upon examination of the holotype of C. shunkan (NSMT-P110000, formerly TUFLFB 38063) and syntypes of C. snelliusi (RMNH 20289), concluded that the 2 species can be further distinguished by the extent of scale coverage on ventral side of head (extending to the vertical point of preopercle vs. to the vertical point of the anterior margin of eye) and by the size and number of scales covering the head (numerous small scales vs. fewer, larger scales). Based on the morphological characteristics of “ C. snelliusi ” addressed by Shen (1993) —D VI–I, 10; A I, 8; P1 14—it is likely that this record represents a misidentification of C. shunkan, and the notable difference in pectoral fin element counts (14 vs. 16–19) is presumed to be a result of counting error. Delventhal & Mooi (2018) reported possible intraspecific variation in the fusion state of the sensory papillae rows z and ot, but no such variation was observed in the specimens examined in this study, all specimens examined exhibits the fusion of rows z and ot.