Callogobius falx, Fujiwara & Suzuki & Motomura, 2021

Fujiwara, Kyoji, Suzuki, Toshiyuki & Motomura, Hiroyuki, 2021, Callogobius falx, a new species of goby from southern Japan, Zootaxa 5048 (2), pp. 253-264 : 254-261

Callogobius falx n. sp.

[New English name: Wagtail Goby; new standard Japanese name: Sekirei-haze]

Figures 1–6 ; Table 1

urn:lsid:zoobank.org:act:50599144-F520-48AF-A6BD-FDFE77494A3D

Callogobius sp. 3 : Suzuki et al., 2004: 73, unnumbered fig (underwater photograph: Ishigaki Island, Yaeyama Islands, Japan); Yoshino, 2008: 412, unnumbered figs. (underwater photographs: Ishigaki Island, Yaeyama Islands, Japan); Yoshino, 2018: 414, unnumbered figs. (same as Yoshino, 2008); Suzuki et al., 2021: 79, unnumbered fig. (underwater photograph: Okinawa Island, Okinawa Islands, Japan)

Callogobius stellatus (non McKinney & Lachner, 1978b): Allen & Erdmann, 2012: 967, unnumbered fig. (underwater photograph: Anilao, Luzon Island, Philippines)

Callogobius sp. : Hayashi & Shiratori, 2003: 211, unnumbered fig. (underwater photograph: Ishigaki Island, Yaeyama Islands, Japan); Hayashi & Shiratori, 2013: 211, unnumbered fig. (underwater photograph: Ishigaki Island, Yaeyama Islands, Japan); Koeda et al., 2016: 89, fig. 408 (listed, based on KAUM–I. 78359, Yonaguni Island, Yaeyama Islands, Japan)

Holotype. OMNH-P 33597 , 23.1 mm SL, Nagura Bay , Ishigaki Island , Yaeyama Islands , Okinawa, Japan, hand net, T. Suzuki (purchased at local aquarium shop at Ishigaki Island), July 2007.

Paratype. KAUM –I. 78359, 14.4 mm SL, Kubura Port , Yonaguni Island, Yaeyama Islands, Okinawa, Japan, 24°26′35″N, 122°56′22″E, hand net, 22 m , T. Yoshida & K. Koeda, 18 Sept. 2015 .

Diagnosis. A species of Callogobius ( Fig. 1 ) characterized by the following combination of characters: dorsalfin rays VI-I, 8 or 9; anal-fin rays I, 7; pectoral-fin rays 18 or 19; lateral scale rows 20–22; body depth moderate, neither particularly slender nor deep (depth at pelvic-fin origin 18.3–20.0% of SL); pelvic-fin base with frenum; caudal-fin length moderate, margin rounded; cephalic sensory-canal pores absent; interorbital papillae row (Row 3) separated, forming two rows (one row in 14.4 mm paratype); postorbital papillae row (Row17) not continuous with upper cranial papillae row (Row 18); preopercular and transverse opercular papillae rows (Rows 20 and 21, respectively) connected, forming single transverse row; body with three oblique black bars, angled upwards anteriorly and continuous with black bars on dorsal fins, anteriormost bar extending from 1 st dorsal fin to midline of body, posterior two bars extending from second dorsal fin to dorsal surface of body and caudal peduncle, respectively; pectoral fin white, upper half widely (ca. 1/2 length of rays) margined with black; caudal-fin base with narrow sickle-like bar.

Description. Dorsal-fin rays VI-I, 9 (8); anal-fin rays I, 7; pectoral-fin rays 19 (18); pelvic-fin rays I, 5; lateral scale rows 22 (20, counted on right side); transverse scales 9 (damaged in paratype); predorsal scale rows 9. Proportional measurements given in Table 1 .

Body slender, subcylindrical anteriorly, compressed posteriorly ( Figs. 1 , 2 ). Anus located just before anal-fin origin. Head relatively large, slightly depressed anteriorly. Snout moderate (slightly shorter than eye diameter), rounded. Eye large, located dorsolaterally. Interorbital region somewhat broad (relatively narrow), flattened. Anterior and posterior nostrils close to each other, latter slightly larger than former, both with a membranous tube; former located on anterior tip of snout, latter midway between anterior nostril and orbit. Mouth small, terminal, inclined anterodorsally, forming angle of ca. 60° with body axis. Upper jaw thick, length moderate (slightly shorter than snout length), its posterior tip rounded, reaching to vertical through posterior nostril. Both jaws with 2 or 3 rows of small, slender conical teeth, tips of each slightly incurved posteriorly; teeth on outermost row on jaws larger than teeth on inner rows. Tongue rounded. Gill membranes attached anteriorly to isthmus. Gill opening narrow, anteroventral point located posterior to vertical level of preopercular margin.

Head sensory-canal pores absent. Sensory papillae on head well developed, forming raised ridges ( Fig. 3 ); postnasal rows (Row 2) long, joined across dorsal midline (separated; Fig. 4 ); interorbital papillae row (Row 3) separated, forming two rows (not separated; Fig. 4 ), anterior row slightly longer than posterior row, both rows on each side very close, but not connected; anterior suborbital (Row 9) and mid suborbital (Row 10) rows moderately long, upper tip of latter reaching to eye; posterior suborbital row (Row 11) separated into two short rows of combined length subequal to upper longitudinal premaxillary row (Row 6); maxillary row (Row 14) continuous, extending from posterior tip of jaws to just below transverse cheek row (Row 13); longitudinal mandibular row (Row 15) continuous; transverse mandibular row (Row 16) including 12 short rows on each side; postorbital papillae row (Row17) moderately long, not continuous with upper cranial papillae row (Row 18); preopercular and transverse opercular papillae rows (Rows 20 and 21, respectively) connected, forming single long transverse row (damaged in paratype), upper tip not articulating with lower cranial row (Row 19).

Large cycloid scales covering nape, prepelvic region, and anterior part of body; cheek and opercle with relatively large, embedded cycloid scales; scales on body becoming ctenoid posteriorly below level of second dorsal-fin base, ctenii of caudal-peduncle scales slightly more elongated; all scales deciduous.

First dorsal fin squarish, 2 nd and 3 rd spines longest, thereafter becoming shorter posteriorly; all spines lacking filamentous tips; dorsal-fin origin located slightly posterior to vertical through pectoral-fin base. Second dorsal and anal fins relatively short with rounded margin, origin of latter slightly posterior to vertical through 2 nd dorsal-fin origin; all soft ray tips (except for last ray) with two branches, last rays branched to base; 2 nd and 3 rd dorsal-fin soft rays longest (longer than dorsal-fin spines), thereafter becoming shorter posteriorly; last anal-fin soft ray located just below base of 7 th (8 th) dorsal-fin soft ray. Pectoral fin rounded, very large, tips reaching to above 4 th (8 th) anal-fin soft ray; all rays branched, connected by membrane. Pelvic fins fused medially with connecting membrane between innermost rays and well developed frenum between spines; posterior margin rounded, reaching below 2 nd dorsal-fin origin (2 nd dorsal-fin soft ray) when appressed; pelvic-fin origin anterior to vertical through ventral end of pectoralfin base; posterior margin of pelvic frenum smooth, slightly emarginated; all segmented pelvic-fin rays branched. Caudal fin rounded, moderate in size, its length slightly larger than head length.

Color when fresh. Based on Figures 1 , 2 . Head light brown dorsally, white ventrally with two black oblique bars; anterior bar relatively narrow (width less than pupil diameter), angled upwards posteriorly, extending from middle of upper jaw to behind eye, posterior part of both stripes on each side connected mid-dorsally (separated; Fig. 2C ), forming U-shaped marking; posterior bar angled downwards posteriorly, extending from just above pupil to around lower edge of opercle, its width very narrow anteriorly, becoming wider posteriorly (width subequal to pupil diameter), intersected on mid-interorbital region. Black trapezoid-like blotch on posterior part of nape, its width subequal to (smaller than; Fig. 2A ) eye diameter, anterior and posterior margins distinctly and slightly emarginated, respectively, lower margin horizontally level with upper end of pectoral-fin base. Body white with three oblique black bars, angled upwards anteriorly and continuous with black bars on dorsal fins; anteriormost bar extending from upper part of 1 st spine of 1 st dorsal fin to midline of body through center of first dorsal-fin base; middle bar short, extending from lower part (including base) of 1 st spine of 2 nd dorsal fin to dorsal surface of body, posterior tip reaching just below 5 th (4 th) dorsal-fin soft ray, its width slightly narrower than anterior bar, subequal to pupil diameter; posteriormost bar wide (width subequal to eye diameter), extending from anterodorsal margin of 2 nd dorsal fin to mid-ventral region of caudal peduncle through posterior part of 2 nd dorsal-fin base (bar tapering posteriorly, bending at center of caudal peduncle; Fig. 2A ). Small poorly defined black blotch above anal-fin origin (absent; Fig. 2A ). All fins white basally; posterior margins of vertical fins, except caudal fin, with small faint black spots (spots absent, 1 st dorsal-fin margin brownish yellow; Fig. 2A ); upper half of pectoral fin widely (ca. 1/2 length of rays) margined with black; caudal-fin base with narrow black sickle-like bar; large, poorly defined black blotch (ca. 1/2 size of fin) on center of caudal fin.

Color in alcohol. Head and body pale whitish-brown. All bars and blotches of fresh specimens retained as dark brown.

Distribution. Currently known only from southern Japan and Luzon, the Philippines ( Allen & Erdmann, 2012; this study). In Japanese waters, the species has been recorded from Hachijo Island (Izu Islands), Kashiwa Island (Shikoku), Kakeroma and Okinoerabu islands (Amami Islands), Okinawa, Ie, and Kume islands (Okinawa Islands), and Ishigaki and Yonaguni islands (Yaeyama Islands) in depths of 12–22 m (KPM-NR 36624, 43551, 54505, 57185, 84845; Hayashi & Shiratori, 2003, 2013; Suzuki et al., 2004, 2021; Yoshino, 2008, 2018; Koeda et al., 2016; Figs. 5 , 6 ).

Etymology. The specific name, falx , a Latin noun meaning “sickle,” refers to the characteristic narrow bar on the caudal-fin base of the new species.

Comparisons. Although C. falx is most similar to C. plumatus and Callogobius sheni Chen, Chen & Fang, 2006 in coloration (e.g., bar patterns and pectoral-fin pigmentation), it differs from both in having 20–22 lateral scale rows (vs. 30–33 in C. plumatus and 27 or 28 in C. sheni ), a narrow sickle-like bar on the caudal-fin base (vs. wide barrel- or diamond-like bar), and no cephalic sensory-canal pores (vs. pores present on anterior oculoscapular canal) ( Smith, 1959; Chen et al., 2006; Figs. 1–4 , 7 , 8 ). Furthermore, the following conditions of the sensory-papillae rows on the head of C. falx also differ from the other two species: Row 3 is separated into two rows (one row in 14.4 mm paratype, possibly due to its small size) (vs. consistently a single row in C. plumatus and C. sheni ) and Row 17 is not continuous with Row 18 (vs. middle of Row 17 continuous with anterior tip of Row 18 in C. sheni ) ( Chen et al., 2006: fig. 1; Figs. 3 , 4 , 8 ).

To date, four species of Callogobius are known to lack cephalic sensory-canal pores (reviewed by Delventhal & Mooi, 2013): Callogobius clarki ( Goren, 1978) , Callogobius crassus McKinney & Lachner, 1984 , Callogobius hastatus McKinney & Lachner, 1978a , and Callogobius winterbottomi Delventhal & Mooi, 2013 ( Delventhal & Mooi, 2013; Allen et al., 2020; Akihito & Ikeda, 2021). Callogobius falx , the fifth known species to lack canal pores, clearly differs from the others in coloration and many morphological characters [e.g., body appearance (moderate depth, neither particularly slender nor deep), presence of pelvic frenum, caudal fin (moderate size, not pointed) and sensory-papillae rows (Rows 20 and 21 connected, forming a single transverse row)] ( McKinney & Lachner, 1978a, 1984; Delventhal & Mooi, 2013; Delventhal et al., 2016; this study). Although Allen & Erdmann (2012) identified an underwater photograph taken at Luzon Island as Callogobius stellatus McKinney & Lachner, 1978b , that species was identified here as C. falx . Callogobius stellatus is readily distinguished from the new species by its very slender body and the presence of one or two relatively large oblong blotches anteriorly on the pectoral fin ( McKinney & Lachner, 1978b: fig. 1; this study).

Figures

FIGURE 1.Fresh (A) and preserved (B, C) holotype of Callogobius falx, OMNH-P33597, 23.1 mm SL, Ishigaki Island,Yaeyama Islands, Okinawa, Japan. (A, B): lateral view; (C): dorsal view.

FIGURE 2. Fresh (A) and preserved (B, C) paratype of Callogobius falx, KAUM–I. 78359, 14.4 mm SL,Yonaguni Island, Yaeyama Islands, Okinawa, Japan. (A, B): lateral view; (C): dorsal view.

FIGURE 3. Photographs of head of Callogobius falx (OMNH-P 33597, 23.1 mm SL), showing cephalic sensorysystem. Sensory papillae rows expressed as black and red numbers (following Delventhal & Mooi, 2013: fig.5, table 2), the latter indicating rows regarded as diagnostic of the new species. AN and PN indicate anterior and posterior nostrils, respectively.

FIGURE 4. Photograph of head of Callogobius falx (KAUM–I. 78359, 14.4 mm SL), showing variations insensory papillae rows 2 and 3.

FIGURE 5. Underwater photograph of Callogobius falx, Okinoerabu Island, Amami Islands, Kagoshima, Japan (specimen not collected). Photo by K. Uehara.

FIGURE 6. Distributional map of Callogobius falx. Red stars: records based on specimens examined in this study; red circles: records based on photographs.

FIGURE 7. Preserved type specimens of Callogobius plumatus. (A): SAIAB 208, holotype, 36.4 mm SL, Cape Delgado, Mozambique; (B): SAIAB 736, paratype, 21.5 mm SL, Cape Delgado, Mozambique. Black brokenlines indicate extent of bar on caudal-fin base.

FIGURE 8. Photographs of heads of Callogobius plumatus, showing cephalic sensory system (holotype: left side; paratype: right side). Red and yellow labels indicate canal pores and papillae rows (in part), respectively (following Akihito & Meguro, 1977 and Delventhal & Mooi, 2013: fig. 5, table 2).