Callogobius clitellus McKinney & Lachner, 1978

(Figs. 5–7; Table 2)

Callogobius clitellus McKinney & Lachner, 1978: 212, fig. 5 (type locality: Madang Harbor, New Guinea); Allen & Erdman, 2012 (East Indies); Delventhal & Mooi, 2013.

Materials Examined

NTOUP2003-11-284, female, 1 (34.6 mm SL); Yufu Village, Shiao-Liu-Chiu Island, Pingtung County, Taiwan; coll. I-S. Chen et al., 11 Nov. 2003 ; NTOUP2007-10-015, male, 1 (35.0 mm SL); Yufu Village, Shiao-Liu-Chiu Island, Pingtung County, Taiwan; coll. I-S. Chen et al., 12 Dec. 2003 .

Diagnosis

Callogobius clitellus can be distinguished from its congeners by the following unique combination of characters: (1) D VI-I, 10; A I, 8; P1 17; P2; I, 5; LR 44–43; TR 22–21; D-P 11; Pred 22–23; V 10+16=26; P-V 3/22110/9; (2) head lateral-line system: papillae ridge row i in 12 rows of short, transverse flaps; (3) Body completely covered in small cycloid scales; and (3) specific coloration pattern: body strongly bicolored with dark brown saddle-like bars, with head having broad brown bars above cephalic region, forming a horse-shoe like marking.

Redescription

Body proportions as shown in Table 2. Body slightly elongated, slightly cylindrical anteriorly and laterally compressed posteriorly. Head depressed; both anterior and posterior nostril openings in short tubes with anterior tube reaching upper lip when depressed; mouth relatively small with posterior end of gape not reaching anterior margin of orbit; snout pointy; body deep and slightly compressed, lateral line vague; vertebrae 10+16.

Fins. First dorsal fin elements VI (2); second dorsal fin elements I, 10 (2); anal fin elements I, 8* (2); pectoral fin elements 17 (2); pelvic fin elements I, 5 (2). D VI-I, 10 A I, 9 P 16, V I, 5. First and second dorsal fins in same height. Second dorsal fin base longer than anal fin base; origin of second dorsal fin extending just slightly before anus. Longest anal fin ray reaching posterior end of caudal peduncle. Pelvic fins separated, spines not connected by frenum but innermost ray connected with a very low membrane (Fig. 7), longest pelvic fin ray almost reaching anus. Pectoral fins reaching vertical position of anus. Caudal fin longer than head, with median rays slightly elongated, resulting in a slight lanceolate shape.

Squamation. LR 43 (1) or 44 (1); TR 22; D-P 11; Pred 22 (1) or 23 (2). Body completely covered in cycloid scales, irregularly arranged. All scales small in size except for those on posterior half of caudal peduncle slightly enlarged towards caudal fin base. Head scaled on predorsal regions, postorbital regions, below orbit, and upper operculum. Fleshy pectoral fin base with several cycloid scales.

Head lateral line system.

Canals.—Head lateral line systems including oculoscapular canal openings (sensory pores) and sensory papillae ridge patterns shown in Fig. 6. Sensory pores with simple, non-tubular opening. Anterior oculoscapular canals present with paired openings pores σ (located at anterior edge of orbit) and unpaired pores λ and κ (located at interorbital region). Postorbital anterior oculoscapular canal with paired pores ω and α. Postorbital part of anterior oculoscapular canal paired pores β and ρ located above preopercle. Preopercular canals with paired pores γ, δ and ε. Posterior oculoscapular canal absent. Anterior oculoscapular canals not continuous with preopercular canals.

Sensory papillae. —Most sensory papillae rows in single rows and located on raised ridges of skin flaps, with some rows in single rows of papillae without ridges. Postorbital row n separated into two sections. Row r separated into two sections, r 1 (located beside nasal region) and r 2 (located at the anterior end of interorbital region), with row r 2 further separated into left and right sections. Cheek with horizontal rows b and d, separating vertical row 4 into 4s (further separated into 4s 1 and 4s 2, lined longitudinally) and 4i; row d and row e not separated into two segments. Rows z and ot joined together, forming a single skin ridge of z+ot. Row i in form of a row of 12 short flaps arranged longitudinally, each flap with 4–5 papillae. Lower jaw with single row f, arranged longitudinally. Vertical rows of papillae located transversely along middle line of body laterally.

Coloration in preservatives. Preserved coloration strongly bicolored; trunk yellowish to milky-orange; two stripes on head running from lower lip, upper lip, eyes until posterior end of opercle, these bars slightly thicker than orbit except bars around orbit, narrowing down to width equal to orbit; predorsal regions with a thick bar running transversely from left pectoral fin base to another, width about 1.5 times orbit diameter, this bar joined with two head stripes forming a horseshoe-like marking on head; chin with a little square-shaped blotch located between origin of two head stripes; pectoral fins with one oblique stripe running from base of first fin ray to end of 11th–12th ray; first dorsal fin with thick band running from middle of first spine to mid-line of trunk, extending from fourth ray anteriorly to posterior end of first dorsal fin base; second dorsal fin with thick oblique bar running downwards from middle of first ray to middle of fourth anal fin ray, band extending from posterior end of anal fin to posterior end of second dorsal fin; posterior end of caudal peduncle with a thin transverse stripe, connecting to longitudinal band on caudal fin; caudal fin band loosely mottled with white circular spots.

Distribution and habitat

Callogobius clitellus has a distribution in Western Pacific from Vietnam, Philippines, Flores Island (Indonesia) to Papua New Guinea, Solomon Islands and Palau (Eschmeyer & Fricke 2023). This species has been so far only documented from our specimen collections obtained from Shiao-Liu-Chiu Island, a small island surrounded by coralline substrates located on the southern west part of Taiwan. The current record marks the northernmost record of the species.

Remarks

Callogobius clitellus belongs to the hasseltii species group, characterized by having sensory papillae row i in form of 11–13 rows of short flaps. This species was originally documented by Shao et al. (2008) as a shallow reef fish with a distribution in Pingtung County. However, there is currently no reliable specimen record to support this documentation as the listed accession number in Shao et al. (2008) (NMMBP-003469) is lost in the specimen archives of the Pisces collection of NMMB, and no description was given for the specimens. Hence, we designate the current 2 specimens we have collected as the first specimen-based record of C. clitellus in Taiwan.