Fusigobius humerosus Kovačić, Bogorodsky & Alpermann, 2023

Bogorodsky, Sergey V., Kovačić, Marcelo, Mal, Ahmad O. & Alpermann, Tilman J., 2023, A new species of Fusigobius (Teleostei: Gobiidae) from the Red Sea and Gulf of Aden, Zootaxa 5256 (2), pp. 101-124 : 106-114

Fusigobius humerosus Kovačić, Bogorodsky & Alpermann sp. nov.

Red Sea Shoulderspot Sandgoby

( Figures 2–5 , 6A & C , Table 1 )

Fusigobius humeralis (non Randall) — Randall 2001: 212 (in part, Red Sea & Gulf of Aden); Ryanskiy 2022: 105, line 2, left (Sharm el Naga, Egypt).

Fusigobius longispinus (non Goren) — Lips et al. 2016: 96 (Arta, Djibouti).

Fusigobius maximus (non Randall) — Ryanskiy 2022: 105, line 3, left (Sinai).

Holotype. SMF 35901 (sample number KAU17-167), male, 28.7 + 8.0 mm, Red Sea , Saudi Arabia, northern side of Farasan Island, a small sand patch at wreck, 16°54.789’N, 41°50.494’E, 4–5 m, T.J. Alpermann, S.V. Bogorodsky & M. Sonnewald, 09 February 2017.

Paratypes, all from the Red Sea. KAUMM 199 , female, 27.6 + 7.9 mm, Saudi Arabia, Al Lith, 20°14.725’N, 040°00.057’E, 8 m, fringing reef, coll . T.J. Alpermann & S . V. Bogorodsky , 19 June 2013 ; KAUMM 463 (sample number KAU12-91), male, 31.2 + 8.2 mm, Farasan Isl. , Mazaghef, 16°35.939’N, 42°20.076’E, 6–8 m, coll . T.J. Alpermann & S . V. Bogorodsky , 19 February 2012 ; PMR VP5271 , 2 females, 25.2 + 6.3, and 25.0 + 6.4 mm and male, 26.4 + 7.3 mm, Saudi Arabia, northern side of Farasan Island , 16°54.789’N, 41°50.494’E, 4–5 m, coll . T.J. Alpermann & S . V. Bogorodsky , 09 February 2017 ; PMR VP5272 , male, 24.1 + 6.7 mm, Saudi Arabia, Al Lith , 20°07.941’N, 40°05.927’E, 6–8 m, a small isolated coral reef, coll . T.J. Alpermann & S . V. Bogorodsky , 16 November 2014 ; SMF 35224 , female, 23.2 + 6.4 mm, Saudi Arabia, Duba, 27°05’42.32”N, 35°46’42.39”E, 13–15 m, coral block on steep slope of island, coll. S . V. Bogorodsky , 19 June 2013 ; SMF 35902 , female, 22.1 + 6.2 mm, and male, 25.1 + 7.4 mm, Farasan Isl. , Abkar I., 16°37.123’N, 041°56.038’E, 7 m, coll . T.J. Alpermann & S . V. Bogorodsky, 27 February 2012 (used only to study morphological characters in the mouth cavity and gill chamber); SMF 35904 (sample number KAU12-40), female, 28.2 + 7.0 mm, Farasan Isl. , Mazaghef, 16°35.939’N, 42°20.076’E, 6–8 m, coll . T.J. Alpermann & S . V. Bogorodsky , 19 February 2012 ; SMF 35905 , female, 20.9 + 5.7 mm, Farasan Isl. , 16°54.933’N, 041°50.761’E, 7 m, isolated coral block, coll . T.J. Alpermann & S . V. Bogorodsky , 02 April 2011 .

Non-type material. Red Sea: BPBM 18272 , female, 23.5 mm, caudal fin damaged, Gulf of Aqaba , Israel ; BPBM 35714 , female, 25.6 + 6.9 mm, Hanish group, Yemen ; KAUMM 464 , 2 males, 24.7 + 7.5 mm and 24.4 + 7.4 mm, and 2 females, 20.9 + 6.5 mm and 18.7 mm + caudal fin damaged, Saudi Arabia, Amaq , 7 m, coll . T.J. Alpermann & S . V. Bogorodsky, 31 March 2011 ; KAUMM 465 , female, 20.2 + 6.3 mm, Saudi Arabia, Al Lith , 6–9 m, coll . T.J. Alpermann & S . V. Bogorodsky, 18 November 2014 ; KAUMM 466 (sample number KAU12-443), male, 26.2 + 7.0 mm, Saudi Arabia, Farasan Arch. , 26 February 2012 ; KAUMM 467 (sample number KAU12-445), female, 26.6 + 7.8 mm, Saudi Arabia, Farasan Arch. , 6–8 m, coll . T.J. Alpermann & S . V. Bogorodsky, 26 February 2012 ; SMF 35207 , male, 19.0 + 5.2 mm, Saudi Arabia, Al Khoreybah , 8–12 m, coll. S . V. Bogorodsky, 23 June 2013 ; SMF 35906 , 2 males, 31.5 + 8.9 mm and 23.4 + 7.3 mm, and female, 21.9 + 6.8 mm, Saudi Arabia, Al Lith , 8 m, coll . T.J. Alpermann & S . V. Bogorodsky, 05 March 2012 ; SMF 35907 , female, 22.1 + 6.9 mm, Saudi Arabia, Rabigh , 10 m, coll . T.J. Alpermann & S . V. Bogorodsky, 08 April 2011 ; SMF 35908 (sample number KAU12-442), male, 29.8 + 7.8 mm, Saudi Arabia, Farasan Arch. , 6-8 m, coll . T.J. Alpermann & S . V. Bogorodsky, 26 February 2012 ; SMF 35909 (sample number KAU12-444), male, 24.3 + 6.8 mm, Saudi Arabia, Farasan Arch. , 6–8 m, coll . T.J. Alpermann & S . V. Bogorodsky, 26 February 2012 ; SMF 35910 (sample number KAU12-446), female, 27.4 + 7.3 mm, Saudi Arabia, Farasan Arch. , 6–8 m, coll . T.J. Alpermann & S . V. Bogorodsky, 26 February 2012 . Gulf of Aden : BPBM 35726 , male, 28.2 + 8.1 mm, Djibouti .

Diagnosis. Dorsal-fin rays VI+I,8–9; anal-fin rays I,8; pectoral-fin rays 17–18; first dorsal-fin spine longest, 1.4–1.6 in head length, 19.9–23.6% SL, subsequent spines progressively shorter; first and second dorsal-fin spines not elongate or filamentous; first dorsal fin slightly higher than second in females, about equal in males; anal-fin spine length 3.4–3.9 in head length; pelvic fins noticeably joined medially by membrane, fifth ray branched, shortest branch of fifth pelvic-fin soft ray 83–94% of longest branch of fourth ray, 18.1-22.1% SL; pelvic frenum present, its width at midline about 1/4–1/5 of pelvic-spine length; body depth 4.4–4.9 in SL; snout short, its length 4.0– 4.9 in head length, 12.4–15.3 in SL; posterior nostril about halfway between orbit and anterior nostril ( Fig. 2A ); eye diameter 3.0– 3.2 in head length; upper-jaw length 3.3–3.5 in head length; gill openings extending forward to about half of opercle width from posterior edge of preopercle; longitudinal scale series 26–28; head and predorsal area naked, scales on side of nape usually ending just anterior at line between upper pectoral-fin base and origin of first dorsal fin ( Fig. 2B ) or 1–2 rows of cycloid scales extending forward to above preopercular edge ( Fig. 2C ); body translucent with numerous small dusky orange-yellow spots on head and body, series of melanophores within and adjacent of each spot; a round black spot smaller than or as large as pupil in humeral region just above base of pectoral fin and equal or slightly larger than pupil a black spot at midbase of caudal fin, covering less than 1/3 height of caudal-fin base; first dorsal fin with oblique dusky line from middle of first spine to anterior base of third spine.

Description. Body moderately elongate, body depth 4.4–4.9 in SL, and laterally compressed, width 1.2–1.4 in depth, caudal peduncle narrow, caudal peduncle depth 7.5–9.5 in SL, 2.4–3.2 in head, caudal peduncle length 3.5–3.9 in SL, 1.1–1.2 in head. Head large, length 2.9–3.1 in SL, ventral part and breast broad; head triangular from dorsal view. Head triangular in cross section. Crest or ridge of head absent. Snout moderately short and steep, its length 4.0– 4.9 in head length, 12.4–15.3 in SL. Anterior nostril a nasal tube without process from rim, at level of lower edge of pupil, about equally distant between front of snout at base of upper lip and anterior edge of orbit, reaching to or nearly reaching upper lip. Posterior nostril with a slightly erected rim, dorsoposterior to anterior nostril and about equally distant to orbit and to anterior nostril. Eyes dorsolateral, moderately large, eye diameter is 3.0– 3.2 in head length, orbit projecting slightly above dorsal profile. Interorbital very narrow, 51.3–67.6 in head length. Mouth terminal, oblique. Mouth moderately large, upper jaw 3.3–3.5 in head length, angle of jaws extending posteriorly to between a vertical of anterior edge of eye and of vertical at anterior edge of pupil. Cheek broad.

Upper jaw with outer row of long, slender, well-spaced, incurved conical teeth continuing backwards on side of jaw, middle band of small conical teeth in a few irregular rows, narrowing backwards on side of jaw and inner row of slender, strongly incurved, conical teeth of medium size. Lower jaw with 10–12 well-spaced, long, slender, slightly incurved, conical teeth restricted to a front of jaw; a middle band of small conical teeth in a few irregular rows narrowing and decreasing in number of rows backwards on side of jaw, and an inner row of long, slender, curved teeth. Tongue well developed, with anterior edge rounded and anterior part free from floor of mouth. Branchiostegal membranes fused to isthmus, gill openings extending forward to about half of opercle width from posterior edge of preopercle. Gill rakers 1–2 + 6, pseudobranchial filaments 6. Branchiostegal rays 5. Genital papilla of adult males 3/5 of orbit diameter, of adult females 1/5 to 2/5 of orbit diameter.

Fins. Dorsal-fin rays VI+I,8–9 (holotype 8, paratypes 8: 2, 9: 7); anal-fin rays I,8; branched caudal-fin rays 12–13 (holotype 12, paratypes 12: 8, 13: 1); upper unbranched caudal-fin rays 7–8 (holotype 8, paratypes 7: 1, 8: 8), posterior 2-3 segmented (holotype 3, paratypes 2: 3, 3: 6); lower unbranched caudal-fin rays 5–7 (holotype 5, paratypes 5: 4, 6: 3, 7: 2), posterior 1–2 segmented (holotype 2, paratypes 1: 2, 2: 7). Pectoral-fin rays 17–18 (holotype 18: 2, paratypes 17: 14, 18: 4), upper 2–5 and lowermost 1–2 unbranched. Pelvic fins I,5+5, I. Origin of first dorsal fin slightly behind upper base of pectoral fin, predorsal distance 2.6–2.9 in SL. First dorsal-fin spine longest, 4.2–5.0 in SL, 1.4–1.6 in head length, first and second dorsal-fin spine not elongate or filamentous in both sexes, second to sixth spine progressively diminishing in length. All spines of first dorsal fin barely reaching origin of second dorsal fin when folded down. Last membrane of first dorsal fin separated from origin of second dorsal fin by a space about equal to space of first membrane of second dorsal fin. Spine of second dorsal fin 1.8–2.0 in head. First dorsal fin slightly higher than second in females, about equal in males, although longest dorsal-fin soft ray longer in males, 1.4–1.6 in head length, than in females, 1.7–1.9 in head. Origin of anal fin between vertical at base of first soft ray and vertical of second soft ray of second dorsal fin, preanal length 1.6–1.7 in SL, anal-fin spine 3.4–3.9 in head length, longest anal-fin soft ray longer in males, 1.4–1.7 in head, than in females, 1.8–2.2 in head. Caudal fin rounded, shorter than head, 1.1–1.3 in head length, 3.5–4.0 in SL. Pectoral fins pointed, middle rays longest, 3.2–3.7 in SL. No free pectoral-fin rays. Pectoral fins extending posteriorly well below origin of second dorsal fin. Pelvic fins joined medially by membrane at least 2/3 of pelvic fin length (membrane connection was broken in specimens so exact extend of connection along fin was not determined, but membrane was still visible on rays from origin up to 2/3 of pelvic fin length) possibly to 9/10 of pelvic fin length (length of fifth pelvic-fin soft ray to tip of shortest branch of fifth 83–94% of length of fourth pelvic-fin soft ray to tip). All pelvic-fin rays including fifth ray branched. Pelvic frenum present, width at midline about 1/4–1/5 of pelvic-spine length. Origin of pelvic fins below base of pectoral fins, prepelvic length 2.8–3.0 in SL, pelvic-fin spine 3.9–5.3 in head, fourth pelvic soft ray longest, 3.9–4.9 in SL, longer in males, 1.2–1.4 in head length, than in females, 1.4–1.6 in head, and reaching to origin of anal fin.

Squamation. Body covered with ctenoid scales, cycloid on breast, prepectoral area, above base of pelvic fins and on belly, anterior part of belly naked. Head, including cheek and operculum, and predorsal area naked, scales on side of nape usually ending anterior at line between upper pectoral-fin base and origin of first dorsal fin or 1–2 rows of cycloid scales extending forward to above opercle. No scales on fins except of a few on base of caudal fin, most of which are smaller than scales on body. Longitudinal scale series 26–28 (holotype 26, right side damaged, paratypes 26: 3, 27: 12, 28: 1, right sides of SMF 35904 and KAUMM 463 too damaged for count), transverse scale series 6–7 (holotype 6, paratypes 6: 6, 7: 10, right sides of SMF 35904 and KAUMM 463 too damaged for count); circumpeduncular scales 10–12 (holotype 11, right side damaged, paratypes 10: 1, 11: 5, 12: 3); breast with three scales in longitudinal series and prepectoral area with single vertical row of scales.

Cephalic sensory systems ( Fig. 3 ). All three head canals present: anterior oculoscapular canal with pores B’, C (single), D (single), E, F, G, and H’; posterior oculoscapular canal with pores K’ and L’; preopercular canal with pores M’, N, and O’. Anterior oculoscapular head canal with short side branch to pore E below eye. Rows and number of sensory papillae as follows: (1) preorbital: snout with three rows in median preorbital series, superior row r close on inner side to pore B (1–2), inferior row s with two sections, s 1 (1) below pore B, close to nostrils, s 3 (1) above upper lip. Lateral series c in four parts: superior c 2 (2–3) between anterior and posterior nostrils, middle c 1 (1–2) behind and bellow anterior nostril and inferior upper c 2 (1–2) and lower c 1 (2) above upper lip. (2) suborbital: suborbital rows without transverse proliferations and uniserial. Row a (3) longitudinal without transverse proliferation below rear part of eye; row c (4) longitudinal without transverse proliferation below anterior and middle part of eye, more distant from eye than row a, starting anteriorly at about vertical of front border of eye, posteriorly ending before vertical of row a. Two cp as papillae below first papilla of row b, lower papilla nearly below upper one. Longitudinal row b (6–11) below rear border of eye. Longitudinal row d continuous from anteriorly above posterior part of upper lip along cheek posterior nearly to a vertical at rear edge of eye (17–19) or divided in supralabial part and part on cheek (6+3–9+7). (3) preoperculo-mandibular: external row e and internal row i divided into anterior (e: 11–16, i: 6–8), and posterior sections (e: 14–20, i: 6–7); mental row f longitudinal (1–4). (4) oculoscapular: anterior longitudinal row x 1 (7–12) continuous from above pore G to above halfway between pores H’ and K’, posterior row x 2 (1–4) above pore L’; row z (3–5) from behind pore G downwards to behind pore M’, row q (1–3) behind pore H’, row y (1–2) behind L’. Axillary rows as 1 (5–8), as 2 (5–9), as 3 (6–8) not visible in every specimen, la 1 and la 2 absent. (5) opercular: transverse row ot (12-18); superior longitudinal row os (6–11); inferior longitudinal row oi (5–8) anteriorly starts close to row ot. (6) anterior dorsal: transverse row n behind pore E (1); transverse rows o (1) divided from each other; longitudinal row g (3–4) ends posteriorly laterally and slightly behind row o, longitudinal row m (2–3) behind and below of row g; longitudinal row h discontinuous (2+3–3+3) in front of first dorsal fin.

Color in life and immediately after death ( Fig. 4A & B , Fig. 5 ). Body translucent in live specimens, slightly murky in fresh specimens, with numerous small dusky orange-yellow spots on head and body, series of melanophores within and adjacent of each spot, spots on head irregularly arranged in oblique rows going posterodorsally and posteriorly. Body covered with small silver or bluish reflective markings. Internal organs well visible, especially in live specimens, gills red and peritoneum silvery; body with an internal series of six horizontally-elongate, dark brown blotches along vertebral column and several, irregularly scattered, oval dark brown blotches in lower part of body. A round black spot smaller than or as large as pupil in humeral region just above base of pectoral fin ( Fig. 6A ), a second subequal or slightly larger black spot at midbase of caudal fin, barely visible underwater, more apparent in freshly dead material, covers less than 1/3 of caudal-fin base height ( Fig. 6C ). Seven faint, brown dorsal marks on back, two in front of the first dorsal fin, two more below first dorsal fin, remaining three marks below second dorsal fin, marks extending onto basal part of both fins and more visible in freshly dead material. Upper pectoralfin base with white streak. An oblique blackish bar extending from anteroventral edge of eye across suborbital area ending on upper lip visible in freshly dead specimens but not visible in life. Eyes with uniform brown-orange iris, sometimes suffused with yellow, and green pupil in life, pupil black immediately after death. Sometimes an orange-brown oblique dash starts at the end of jaw extending backwards and up on cheek. Dorsal and caudal fins with orange and yellow dots, except for unspotted ventral one-fourth of caudal fin, the first dorsal fin with variably distinct oblique dusky line from the middle of first spine to anterior base of third spine. Pectoral fins transparent with a white longitudinal stripe at the midline of pectoral-fin base extending into middle of pectoral fin and nearly reaching fin margin. Anal and pelvic fins transparent with snow-white area: origin of anal fin and center of pelvic fin, respectively.

Color preserved ( Fig. 4C ). Body opaque fawn, orange-yellow coloration lost. The pigmented pattern of small spots on head and body brown. A round black spot smaller or as large as pupil in humeral region just above base of pectoral fin ( Fig. 6A ), a second about equal black spot at midbase of caudal fin, covers less than 1/3 of caudal-fin base height, both well visible to less vivid in some specimens ( Fig. 6C ). Eyes dark, including pupil. Oblique brown bar from eye to upper lip, parallel oblique brown bar from end of jaw backwards and up onto cheek. Dorsal fins transparent with dark pigmented pattern extending from the base, more intense on the first dorsal fin, a dark lines extends from the origin of the third spine upward to the upper part of the first spine. Anal fin darkly pigmented in males, poorly pigmented in females. Caudal fin, pectoral fins and pelvic fins transparent, poorly pigmented except for the black spot at origin of caudal fin that extends slightly onto caudal rays.

Etymology. The species name humerosus in reference to resemblance to the sister F. humeralis . Both species share the presence of a distinct black spot in the humeral area above pectoral-fin base.

Distribution and Habitat. At present Fusigobius humerosus is known from the Red Sea, including Gulf of Aqaba, south to the inner Gulf of Aden. Found on sand and rubble near or within coral reefs, at depths of 3– 15 m.

Remarks. Fusigobius humerosus differs from all other Fusigobius species by a combination of external morphological characters and coloration, except from F. gracilis and F. humeralis (e.g., Randall 2001, Figs. 1 –18). The new species is compared with each species below by the set of the most useful characters. Comparison is ordered as in diagnosis, the species descriptions may be found in the following publications ( Günther 1877; Goren 1978; Hoese & Reader 1985; Winterbottom & Emery 1986; Hoese & Obika 1988; Chen & Shao 1997; Randall 1994, 2001, 2005; Allen & Erdmann 2012; Larson 2022).

Fusigobius humerosus differs from F. aureus by pelvic fins joined by membrane, pelvic frenum present (vs. pelvic fins separated, except for the narrow connection, pelvic frenum absent), snout length 4.0– 4.9 in head length (vs. 3.1–3.2 in head length) and longitudinal scale series 26–28 (vs. 23–24). The new species differs from F. duospilus by first dorsal-fin spine longest, longer than second and third (vs. first three spines subequal in length), the shortest branch of fifth pelvic-fin soft ray 83–94% of the longest branch of fourth ray (vs. 2/3 of the longest branch of fourth ray) and longitudinal scale series 26–28 (vs. 22–25, however the method applied by Hoese & Reader (1985) could count 2–3 fewer scales than the present method following Randall (2001) and, counts for the two species may overlap). The new species differs from F. gracilis by pelvic frenum present (vs. pelvic frenum absent), body depth 4.4–4.9 in SL (vs. body slender, its depth 5.6–5.8 in SL) and longitudinal scale series 26–28 (vs. 25). The new species differs from F. inframaculatus by pectoral-fin rays 17–18 (vs. 19), first and second dorsal-fin spines not elongate or filamentous (vs. first and second dorsal-fin spines elongate and first usually filamentous), scales on side of nape not extending forward to above preopercular edge (vs. scales on side of nape extending forward nearly to eye). Fusigobius humerosus differs from F. longispinus by first and second dorsal-fin spines not elongate (vs. first dorsal-fin spine very long, reaching to the rear base of the second dorsal fin), gill openings extending forward to about half of opercle width from posterior edge of preopercle (vs. gill openings reaches only to below pectoral-fin base), longitudinal scale series 26–28 (vs. 25). The new species differs from F. maximus by first dorsal-fin spine longest, remaining spines progressively shorter (vs. second dorsal-fin spine longest, first to fifth spines only slightly shorter than second), first dorsal fin slightly higher than second in females, about equal in males (vs. first dorsal fin lower than second in females, about equal in males), scales on side of nape usually ending anterior at line between upper pectoral-base and first dorsal-fin origin or rarely 1–2 rows of cycloid scales extending to above opercle (vs. scales on side of nape extending forward to above upper end of preopercular margin). The new species differs from F. melacron by dorsal-fin rays VI+I,8–9 (vs. VI+I,10), anal-fin rays I,8 (vs. I,9), pectoral-fin rays 17–18 (vs. 19–21), first dorsal fin slightly higher than second in females, about equal in males (vs. first dorsal fin distinctly higher than second dorsal fin). The new species differs from F. neophytus by eye diameter, 3.0– 3.2 in head length (vs. 3.2–3.7), longitudinal scale series 26–28 (vs. 23–25), scales on side of nape ending anterior at line between upper pectoral-base and first dorsal-fin origin or rarely 1–2 rows of cycloid scales extending above opercle (vs. scales extending forward nearly to eye), operculum naked (vs. operculum rarely with a single scale on the dorsal half). The new species differs from F. pallidus by pectoral-fin rays 17–18 (vs. 19–20), scales on side of nape ending anterior at line between upper pectoral-base and first dorsal-fin origin or rarely 1–2 rows of cycloid scales extends above opercle (vs. scales on side of nape extending forward to above upper end of preopercular margin). The new species differs from F. signipinnis by pelvic fins joined by membrane, pelvic frenum present (vs. pelvic fins nearly fully separated, pelvic frenum absent), longitudinal scale series 26–28 (vs. 21–25, however the method applied by Hoese & Obika (1988) could count 2–3 fewer scales than the present method following Randall (2001) and counts for the two species may overlap).

Fusigobius gracilis , F. humeralis and F. humerosus are very similar in coloration and possess a translucent body with numerous small dusky orange-yellow spots on the head and body combined with a round black spot smaller than or as large as pupil in humeral region just above base of pectoral fin and another slightly larger black spot at midbase of caudal fin. Fusigobius humerosus differs from F. gracilis by having dusky orange-yellow spots with a series of melanophores within and adjacent in each spot vs. numerous very small orange-yellow spots that cover head and body, each containing a single melanophore except for ventral half of the posterior part of body with a longitudinal series of orange-yellow spots surrounded by a series of melanophores, and a distinct patch of melanophores on side of abdomen in F. gracilis . Also iris is usually unicolor in Fusigobius humerosus vs. dorsal iris and dorsal surface of orbit with tiny orange-brown spots in F. gracilis .

The new species differs from the similarly colored F. humeralis ( Fig. 7 ) in minor details of coloration of live individuals: a unicolor iris, rarely suffused with yellow vs. iris with orange-red marks anteriorly and dorsally around eye in F. humeralis . The new species also differs from F. humeralis in the following morphological characters: first dorsal-fin spine longest, 1.4–1.6 in head length, 4.2–5.0 in SL, remaining spines progressively shorter vs. second and third dorsal-fin spines longest and subequal, 1.8–2.5 in head length, 5.1–6.8 in SL; anal-fin spine short, the length 3.4–3.9 in head length vs. 2.5–3.2 in head length; the shortest branch of fifth pelvic-fin ray short, length 18.1–22.1% SL vs. 19.4–27.5% SL (single overlapping value of 19.4% SL was found only in ROM 60914, French Polynesia); posterior nostril about halfway between anterior margin of orbit and anterior nostril vs. posterior nostril closer to orbit than to anterior nostril; upper jaw short, the length 3.3–3.5 in head length vs. 2.5–3.2 in head length; longitudinal scale series 26–28 vs. 23–25; head and predorsal naked, scales on side of nape ending usually anterior at line between upper pectoral-base and first dorsal-fin origin or rarely 1–2 rows of cycloid scales extending above opercle vs. scales on side of nape variably extending forward nearly to eye, to between eye and above preopercular edge or to above preopercular edge. The two species are also delimited by their geographic ranges, F. humerosus is known from the Red Sea and the Gulf of Aden, while F. humeralis is widespread from the Comoros, Maldive Islands and Chagos Archipelago in the western Indian Ocean to French Polynesia in the Pacific Ocean ( Randall 2001, present research).

Size of the spot in humeral area and spot at caudal-fin base may be useful characters to differentiate F. humerosus from F. humeralis , with exceptions of some specimens of the latter species showing overlapping characters. The round black spot in humeral region just above the pectoral-fin base is smaller or as large as pupil in F. humerosus vs. dark spot usually larger than pupil in F. humeralis (with the exception of some comparative specimens having dark spot size of pupil or slightly smaller: ROM 85028, Indonesia; ROM 81801 and ROM 81686, Palau; ROM 64085, New Caledonia; and ROM 37240, ROM 37241, ROM 37243, ROM 37244, Chagos Archipelago). The oval black spot at midbase of caudal fin covers less than 1/3 of caudal-fin base height in F. humerosus vs. irregular spot at midbase of caudal fin larger than 1/3 of caudal-fin base height in F. humeralis (except for some specimens where it is equal to but not less than 1/3 of caudal-fin base height: ROM 85028, Indonesia; ROM 81801 and ROM 81686, Palau; Fig. 6B & D ).

Randall (2001) noted that specimens from the Red Sea and Gulf of Aden, which were described as non-types, have 17 pectoral-fin rays whereas specimens from the Indo-West Pacific usually have 18 rays. Re-examination of Randall’s material and additional Red Sea material of the new species confirmed possessing usually of 17 rays. This material was added as non-type material of F. humerosus in the present new species description.

Specimens of Fusigobius humerosus from the Red Sea and Gulf of Aden have been incorrectly identified as F. humeralis . Along with the above morphological evidence, both molecular approaches for the species delimitation (i.e. ABGD and PTP) recognized the new species as an independent lineage at species level (see Fig. 1 ). The phylogenetic analysis of mitochondrial COI showed that sequences generated from the type specimens of Fusigobius humerosus formed a monophyletic clade with other sequences of Red Sea origin. The resulting clade was sister to a clade composed of Fusigobius humeralis from French Polynesia and Taiwan. Unfortunately, no tissue material was available from or close to the type locality of F. humeralis (i.e. Maldives). However, the identities of the two most distant specimens (from French Polynesia) were confirmed by images in BOLD and by the original identifier based on distinguishing characters as defined herein (J.T. Williams, pers. comm.).

Figures

FIGURE 1. Maximum likelihood tree estimated from the barcoding region of the mitochondrial COI gene displaying phylogenetic relationships among haplotypes from Fusigobius species.The holotype of the new species F. humerosus sp. nov. is printed in bold. Branch length is proportional to the estimated number of average nucleotide substitutions. Numbers at branches represent bootstrap proportions in percentages. Values <50% are not shown. Results from species delimitation analyses based on COI gene sequences using the ABGD and bPTP algorithms are displayed as vertical bars that link terminal taxa in the tree if assigned to the same hypothetical species.

FIGURE 2. Fusigobius humerosus sp. nov. Paratype, KAUMM 199, female, 27.6 + 7.9 mm, Al Lith, Saudi Arabia, Red Sea: A: the origin of posterior nostril about equal to orbit and to the origin of anterior nostril, the origin of nostrils and the edge of orbit outlined; B: 1–2 rows of cycloid scales extends above opercle. C: Paratype, PMR VP5272, male, 24.1 + 6.7 mm, Al Lith, Saudi Arabia, Red Sea, the scales ending anterior at line between upper pectoral-fin base and first dorsal fin origin. The anteriormost scales marked with arrow. Photos by M. Kovačić.

FIGURE 3. Cephalic sensory pores system and papillae of Fusigobius humerosus sp. nov. Paratype, KAUMM 199, female, 27.6 + 7.9 mm, Al Lith, Saudi Arabia, Red Sea. Terminology in text. Drawing by M. Kovačić.

FIGURE 4. Fusigobius humerosus sp. nov. holotype, SMF 35901, male, 28.7 + 8.0 mm, northern side of Farasan Island, Saudi Arabia, Red Sea, A: live specimen, B: freshly collected, C: preserved specimen. Photos by S.V. Bogorodsky (A & B) and M. Kovačić (C).

FIGURE 5. Fusigobius humerosus sp. nov., underwater photographs of uncollected individuals. A: Dahab, Egypt, Red Sea; B: Al Wajh, Saudi Arabia, Red Sea; C: Mangrove Bay, El Quseir, Egypt, Red Sea. Photos by S.V. Bogorodsky.

FIGURE 6. A and C: Fusigobius humerosus sp. nov., PMR VP5271, paratype, male, 26.2 + 7.3 mm, northern side of Farasan Island, Saudi Arabia, Red Sea. B and D: F. humeralis, BPBM 36627, paratype, female, 29.5 + 7.8 mm, Manuk Island, Banda Sea, Indonesia. Humeral region just above base of pectoral fin. A: round black spot is smaller than or equal to pupil in F. humerosus sp. nov., B: dark spot larger than pupil in F. humeralis; midbase of caudal fin: C: oval black spot covers less than 1/3 of caudal base height in F. humerosus sp. nov., D: irregular spot at midbase of caudal fin larger than 1/3 of caudal base height in F. humeralis.

FIGURE 7. Fusigobius humeralis. A: BPBM 32955, holotype, 28 mm SL, South MaleAtoll, Maldives; B: USNM 439586, 25.7 mm SL, Moorea, Society Islands; C: Ngulu Atoll, Micronesia; D: Raja Ampat Is., West Papua, Indonesia. Photos by J.E. Randall (A), J.T. Williams (B) and G.R. Allen (C & D).