Cabillus nigrostigmus, Kovačić, Marcelo & Bogorodsky, Sergey V., 2013

Kovačić, Marcelo & Bogorodsky, Sergey V., 2013, Two new species of Cabillus (Perciformes: Gobiidae) and the first record of Cabillus macrophthalmus from the Western Indian Ocean, Zootaxa 3717 (2), pp. 179-194 : 186-191

Cabillus nigrostigmus sp.nov.

( Figs. 5–7 )

Holotype. PMR VP2846, female, 37.9+ 9.9 mm, Red Sea, Sharm el Sheikh, Sharm el Moya Bay, 34° 17' 30.94'' N, 27° 51' 30.21'' E, coll. Bogorodsky, S.V., 13 Jul. 2011.

Paratype. PMR VP3046, female, 42.0+ 11.1 mm, Red Sea, Gulf of Aqaba, Dahab, 34° 31' 06.91'' N, 28° 29' 54.14'' E, coll. Bogorodsky, S.V., 13 Nov. 2012.

Diagnosis. Pectoral-fin rays 19; transverse scale series 7; nape scaled, median predorsal scales 7; body depth 5.8–6.0 in SL; snout length 1.5-1.9 in eye diameter.

Description. Body moderately elongate, laterally compressed posteriorly, the depth at pelvic-fin origin 16.7– 17.2 % of SL, width at pectoral-fin origin 17.9–18.6 % of SL. Head length 30.2–30.9 % of SL, head width 1.4–1.5 in head length, head depressed (head width 20.1–21.4 % of SL, head depth 16.6–16.9 % of SL). Snout with moderately sloping profile, short, the length 1.5–1.9 in eye diameter, 6.9–7.1 % of SL. Anterior nostril short, tubular, lacking process from rim. Posterior nostril opening flat. Eyes wide, dorsolateral, eye diameter 2.4–2.9 in head length, 10.5–12.9 % of SL. Interorbital very narrow, less than pupil diameter (width 1.3–1.4 % of SL). Mouth terminal, oblique. Angle of jaws ending posteriorly below anterior half of eye, the upper jaw length 10.6–11.0 % of SL. Rows of pointed teeth in both jaws, outer row the largest. Tongue bilobed. Chin lacking barbels. Branchiostegal membranes fused to isthmus, gill openings end forward at pectoral-fin base. No spines on preopercle. No dermal crest anterior to first dorsal fin. Caudal-peduncle depth 9.0–9.8 % of SL, caudal-peduncle length 22.4–23.6 % of SL, caudal-peduncle depth in its length 2.4–2.5.

Fins: dorsal-fin rays VI + I,9; anal-fin rays I,8; pectoral-fin rays 19; segmented caudal-fin rays 17, branched 14; pelvic-fin rays I/5 + 5/I. The first dorsal-fin base 12.6–14.5 % of SL; the second dorsal-fin base 26.0–26.1 % of SL; anal-fin base 18.8–19.0 % of SL. Dorsal-fin spines thin and flexible. Spines of first dorsal fin not elongate or filamentous, ending backwards before the origin of the first spine of the second dorsal fin when folded down. The first dorsal-fin origin behind vertical of pectoral-fin base. Origin of anal fin posterior to vertical of origin of the second dorsal fin, at the level between the first and second soft ray of the second dorsal fin. Pectoral fins not reaching posteriorly to a vertical of origin of anal fin, ending vertical of anus, length 23.5–25.7 % of SL, pectoralfin rays all branched, upper rays within membrane. Pelvic fin complete, longer than wide, 23.5–27.4 % of SL, reaching anus. Pelvic frenum moderately reduced (minimum pelvic frenum height 1/4–1/3 of pelvic spine length). Caudal fin rounded, shorter than head, 0.85–0.87 of head length, 26.1–26.4 % of SL.

Scales: body covered with ctenoid scales, except cycloid on nape, prepelvic area and abdomen. Longitudinal scale series 27–30, transverse scale series 7. Predorsal scaled, median predorsal scales 7, scaled area ending forward between the posterior margin of preopercle and opercle. Prepelvic area scaled, prepelvic scales at ventral median 5. Opercle and cheek naked. No modified scales with enlarged ctenii at the caudal-fin base.

Cephalic sensory systems: head with anterior oculoscapular and preopercular canals, with pores σ, λ, κ, ω, α, β, ρ, and γ, δ, ε respectively. Rows of head sensory papillae ( Fig. 7 ). Preorbital: upper row r (1–3) above level of pore σ; upper row s1 has two papillae at pore σ, row s2 as single papilla below pore σ, and lower row s3 (6–7) horizontal above upper lip. Lateral series c in three parts: superior c2 (3–4) below posterior nostril; middle c1 (1–5) behind anterior nostril; inferior upper c2 (5–9) as longitudinal row above upper lip, anterior and above to row c1, inferior lower row c1 has two papillae above upper lip. Suborbital rows: row a (8–12) single longitudinal row below eye from about anterior edge of pupil to posterior end of eye. Row b (18–25) longitudinal, beginning below anterior edge of eye or in front of it, ending below posterior edge of eye. Row c (11–12) single longitudinal row starting bellow between anterior edge of eye and anterior edge of pupil, ending posteriorly more or less bellow end of row b. Row d (16–23) continuous from above upper lip, ending backwards below the posterior part of pupil. Preoperculo - mandibular rows: external row e (19+18 to 20+27); and internal row i (12+9 to 15+15) divided into anterior and posterior sections; mental row f (6–7) longitudinal. Oculoscapular rows partially visible in holotype but clearly visible in paratype. In holotype the number of papillae in some rows could be higher than the visible count: anterior longitudinal row x1 (7) starting anteriorly above pore ρ and going backwards, separate from posterior longitudinal row x2 (3); row z (2–4) between pores γ and ρ; row q longitudinal row (9) behind pore ρ in the paratype, but just as two papillae visible in holotype; row y (4) longitudinal bellow row x2, not visible in holotype; transversal axillary rows as1 (2–3), as2 (3–5), as3 (3–7) present; axillary row la1 (1–3) present above as2; axillary row la2 visible just in holotype as single papilla above row as3. Opercular rows: transverse row ot (17–24); superior longitudinal row os (6–15); and inferior longitudinal row oi (5–6). Anterior dorsal rows present in paratype, in holotype not visible probably due to the combination of damaged skin surface and present scales, pigmentation and mucus: anterior transverse row n as single papilla behind pore ω, transverse row o (4); longitudinal row g (3), longitudinal row m (3) below and behind row g, longitudinal row h (3+3) divided.

Colour in life (based on the photo of live holotype and paratype, Figs. 5 A and 6A). Head and body mottled gray, suffused with yellow ventrally. A dark brown bar commencing dorsally on body from fourth dorsal spine to first spine of second dorsal fin, the anterior margin slanting to beneath pectoral fin, the posterior margin vertical to abdomen, then curving obliquely ventrally beneath pectoral fin, ending on lower side of abdomen where bar becoming narrower. Five indistinct, irregular, dark bars along back: first at the first dorsal-fin origin, three below the second dorsal fin and last at the caudal peduncle. Three dark blotches along lateral midline behind broad bar, the dark spot at the end of caudal peduncle is the lowest points of the dark zigzag pattern. The midlateral black spot at the end of caudal peduncle is followed by an S-shaped dark bar, with lower half of the bar on caudal-fin base, upper half extending onto basal part of caudal fin. Predorsal area with scattered melanophores and one brown band above pectoral fins. An oblique dark brown band from upper lip to pupil of eye, broadening on iris behind and above pupil, and continuing as a band across interorbital. Cheek, and opercle more or less pale, with scattered melanophores, except for more pigmented area on lower part of cheek below eye, and a dark mark at lower opercle. The postorbital head and operculum suffused with pink. Dorsoanterior oblique zone of eye white. The first dorsal fin pigmented at tip between the first and fourth spine and with elongate black blotch along posterior basal part, continuing halfway between sixth spine and spine of second dorsal fin, with the sixth spine and adjacent membranes dark. The second dorsal fin transparent, with rarely scattered dark dots. Caudal fin transparent, with the described S-shaped dark bar at the caudal-fin base and poorly pigmented vertical rows of dots behind. Pectoral fins transparent and poorly pigmented, except for a brown, deeper than longer, oval mark at upper pectoral-fin base. Pelvic and anal fins whitish.

Colour preserved. Some coloration details visible in paratype PMR VP3046 ( Fig. 6 C), but lacking in holotype PMR VP2846 ( Fig. 5 B) due to damaged fin membranes and missing scales. Body dusky, with dark colour pattern. Upper part of body with rectangular pattern of melanophores following the edges of scales, lower third of body without pigment. The dark area on the upper part of body below the first dorsal fin and the dark zigzag pattern visible. The midlateral black spot at the end of caudal peduncle and the S-shaped dark bar on the caudal fin intensive and well preserved. Predorsal with scattered melanophores and dark scale edges, more uniformly coloured compared to live coloration, separated from the dark area below the first dorsal fin by the pale diagonal band starting between first to fourth spine of the first dorsal and ending downwards behind pectoral axil. The dark band present between eyes and upper jaw, but the specimen lost the intensive brown bar across eye visible in live specimen. The lower part of cheek below eye more pigmented and the dark mark present at lower opercle. The rest of cheek and opercle with rarely scattered melanophores, but darker compared to live specimen. The body and head ventrally without pigmentation, except for the dark mark on chin. The dorsal and anal fin colouration of preserved specimen based on paratype. The first dorsal fin pigmented at tip between the first and fourth spine and with two pigmented stripes starting at the first spine, and joining posteriorly in a single large dark blotch at lower posterior part of fin. The second dorsal fin with dark dots arranged on membranes between rays. Caudal fin with the Sshaped dark bar at the caudal-fin base and poorly pigmented vertical bands behind it. Pectoral fins pigmented more intensively in the lower part. A large, dark mark present at upper pectoral fin base and origin of upper rays. Pelvic and anal fins darkly pigmented.

Etymology. Named nigrostigmus from the Latin in reference to the distinctive black mark in the lower posterior of the first dorsal fin.

Remarks. Cabillus nigrostigmus is unique among the species of Cabillus , except for C. pexus , C. macrophthalmus and C. atripelvicus , in having median predorsal scales and the absence of posterior oculoscapular canal with pores ρ1, ρ2 (Randall et al. 2007; Shibukawa & Aizawa 2013). Another species without the posterior oculoscapular canal, C. caudimacula , has no median predorsal scales and, unlike C. nigrostigmus , has two large scales with enlarged ctenii at the caudal-fin base.

Cabillus nigromarginatus can be distinguished from C. pexus in having 7 predorsal scales vs 5, and absence of modified scales with enlarged ctenii at the caudal-fin base.

Cabillus nigrostigmus is easily separated from C. atripelvicus by several morphological characters: shorter pectoral fins, reaching to a vertical line at the anus vs. reaching to a vertical line at the origin of anal fin; transverse scale series 7 vs. 9 in C. atripelvicus ; head length 3.2–3.3 in SL vs. 3.35–3.5 in C. atripelvicus ; snout length 1.5–1.9 in eye diameter vs. 1.4–1.5 in C. atripelvicus (calculated from the Table 1 in Randall et al. (2007)) and by coloration. Cabillus atripelvicus has more intensive fin coloration: anal and pelvic fins black, broad horizontal dark brown band across entire lower half of the first dorsal fin, and dark brown bands on the second dorsal fin and caudal fin. The body coloration of C. nigrostigmus is dominated by the broad, dark brown bar on the upper part of body below the first dorsal fin. Cabillus atripelvicus has dark brown blotches of equal intensity along dorsal twothirds of body, forming a bold zigzag pattern, resulting in four clear pale spots along back and five midlateral dark marks (including caudal-fin base mark) as the lowest points of the pigmented area.

Cabillus nigrostigmus resembles in coloration C. macrophthalmus , both have a broad, dark brown bar on upper part of body below first dorsal fin, two dark pigmented bands on the first dorsal fin, and black spot at caudal-fin base; however, they clearly differ in several morphological characters and in coloration pattern details. Cabillus nigrostigmus is a more slender fish with a shorter head compared to C. macrophthalmus : body depth 5.8–6.0 in SL vs. 4.4–5.1 in SL, caudal peduncle depth in its length 2.4–2.5 vs. 1.8–1.9, and head length 3.2–3.3 in SL vs. 2.7–3.0 in SL; pectoral-fin rays 19 vs. 17; median predorsal scales 7 vs 8 or 9; scaled area on nape not reaching forward to a vertical line through posterior margin of preopercle vs. scaled area on nape reaching forward to a vertical line through posterior margin of preopercle. The two species differ by the following coloration characters: broad, dark brown area on upper part of body below first dorsal fin beginning anteriorly at the level of fourth spine of the first dorsal fin in C. nigrostigmus vs. broad, dark brown area on upper part of body continuous anteriorly to predorsal area in C. macrophthalmus ; first dorsal fin pigmented at tip and elongate black blotch present along posterior basal part continuing halfway between sixth spine and spine of second dorsal fin, and sixth spine and adjacent membranes black in C. nigrostigmus vs. first dorsal fin pigmented at tip and with diagonal band anteriorly more intensively pigmented, beginning at about middle of the first spine (males) or at lower part of the first spine (female holotype in drawing in Koumans (1953)), and less intensive backwards, ending at the origin of the sixth spine; midlateral black spot at the end of caudal peduncle followed by S-shaped dark bar, with lower half of the bar on caudal-fin base, upper half extending onto basal part of caudal fin in C. nigrostigmus vs. diffuse pigmentation covering entire height of caudal peduncle at caudal-fin base and no S-shaped dark bar on caudal-fin base and basal part of caudal fin.

Cabillus nigrostigmus is a typical sandy bottom dwelling goby: both specimens were observed in shallow water in open sandy areas, from the Sharm el Moya Bay at depth of 1m, and from Dahab at depth of 6 m, respectively. The goby is active at night and partly borrowes quickly in the sand when alarmed, like dragonets, by shaking the body and digging using large pectoral fins with their thickened membranes.

Figures

FIGURE 5. Cabillus nigrostigmus sp. nov., holotype, PMR VP 2846, female, 37.9 mm SL, Sharm el Moya Bay, Red Sea, A: live specimen; B: preserved specimen. Photos by S. V. Bogorodsky.

FIGURE 6. Cabillus nigrostigmus sp. nov., paratype, PMR VP 3046, female, 42.0 mm SL, Dahab, Red Sea, A: live specimen; B: freshly collected specimen; C: preserved specimen. Photos by S. V. Bogorodsky (A, B), M. Kovačić (C).

FIGURE 7. Cabillus nigrostigmus sp. nov., cephalic sensory canal pores and papillae: holotype, PMR VP 2846, female, 37.9 mm SL, Sharm el Moya Bay, Red Sea. Terminology in text. Drawing by M. Kovačić.