Thorogobius laureatus, Sauberer & Iwamoto & Ahnelt, 2018

Sauberer, Michael, Iwamoto, Tomio & Ahnelt, Harald, 2018, Two new deep-water species of the genus Thorogobius (Teleostei: Gobiidae) from the upper continental slope of the Eastern Central Atlantic, Zootaxa 4429 (2), pp. 357-371 : 366-370

Thorogobius laureatus sp. nov.

( Figures 1 , 4–7 ; Tables 1–3)

Holotype. CAS 243854, male, standard length+caudal fin length 65.1+ 23.1 mm, Angola, sw. of Congo R. mouth, (6°27′S, 11°55′E) from depths of 109– 108 m, R/V Dr. Fridtjof Nansen (DFN) stn. 3783, 22 April 2005.

Paratypes. (10 specimens). Angola: CAS 225191, 1 male 74.0+ 24.2 mm SL+CL, off Cape Santa Maria (11°46.28′S, 13°29.29′E), 165– 164 m, DFN stn. 43, 4 March 2007; CAS 244058 , 1 female 74.9+ 21.5 mm SL+CL, same data as for holotype ; ZSM 32517, 1 female 80.2+ 23.9 mm SL+CL, off Sumbe (11°13′S, 13°36′E), 147– 146 m, DFN stn. 3044, 8 March 2003; ZSM 35530, 1 female 78.0+ 21.8 mm SL+CL, same data as for ZSM 32517 . São Tomé and Príncipe: CAS 243850 , 2 females 58.1+19.3 & 58.5+ 18.8 mm SL+CL, off São Tomé Is. (0°08.7′N, 6°41.7′E), 65– 57 m, DFN stn. 30, 18 May 2010 ; CAS 243851 , 1 male 60.8+ 19.6 mm SL+CL, off São Tomé Is. (0°09.9′N, 6°42.6′E), 65– 64 m, DFN stn. 34, 18 May 2010 ; CAS 243852 , 1 male 58.3+d mm SL+CL, off São Tomé Is. (0°08.84′N, 6°41.8′E), 57–65 m, DFN stn. 40, 19 May 2010 ; CAS 243853 , 1 female 58.8+ 18.4 mm SL+CL, off São Tomé Is. (0°15.8′N, 6°47.1′E), 71– 60 m, DFN stn. 35, 19 May 2010 ; NMW 99080, 1 male 59.1+ 20.9 mm SL+CL, same data as for CAS 243850 ( Fig. 6 ).

Non-type specimens. (4 specimens). Excluded from type material because of damage and/or juvenile stage. CAS 244223, 4 specimens of undetermined sex (35.7–46.9 mm SL), same data as for CAS 243850.

Diagnosis. Thorogobius laureatus sp. nov. is distinguished from its congeners in the combination of following characters: Fins: first dorsal fin with six spiny rays, second and third distinctly elongated; pectoral fin ray count 19–22; pelvic disc complete and short with well-developed anterior membrane (frenum), with pointed lateral lobes. Scales: scales on nape and predorsal area in lateral band; no scales on opercle; scales in longitudinal series 24–27. Pattern of free neuromasts (sensory papillae): supratemporal rows tr and trp developed, extending transversally between pores H and K; longitudinal row g long, passing row m posteriorly and relatively close to row h; infraorbital row 6 long, ventrally extending to lower margin of preopercle, its ventral (6i) and dorsal (6s) originating opposite to each other; posterior lateral rows: row h long, reaching anteriorly above middle of opercle. Body proportions: body depth (18.9–23.8% at anal-fin origin in SL), head width (48.5–56.0% in head length); upper jaw long (41.8–58.0% in head length); minimum height of caudal peduncle (45.1–59.8% in caudal peduncle length); eyes large (23.9–30.9% in head length); caudal fin long (27.9–35.5% in SL). Coloration: body pale fawn and brownish; margin of scale pockets dark brown pigmented, yielding a reticulated pattern; five brown blotches on flanks in lateral midline from below first dorsal fin to caudal peduncle; caudal fin with 6–7 distinct dark vertical bands.

Description. Profile of head steep; dorsal outline of body straight. Tubular anterior nostril short, without process from rim; branchiostegal membrane attached to side of isthmus.

Fins. D1 6 spiny rays (6*: 11); D2 1 spiny and 11 articulated rays (1+11*: 11); anal fin 1 spiny and 10 articulated rays (1+10*: 11); pectoral fin 19–22 articulated rays (19: 1, 20: 5, 21*: 4, 22: 1); dorsalmost rays of pectoral fin within fin membrane; pelvic disc 1 spiny and 5 articulated rays on each side (1+5*: 11); caudal fin 16– 17 segmented rays (16: 1, 17*: 10), 14–15 of them branched (14*: 10, 15: 2). Second to fourth spiny rays of D1 longest; second spiny ray of D1 extremely elongated in males, depressed reaching to end of D2 base; depressed third dorsal spiny ray reaching approximately to half of D2 base. Pelvic disc complete (oval-shaped) with welldeveloped anterior membrane (frenum) that extends over approximately 75% of first (spinous) ray; lobes distinct but narrow and pointed.

Squamation. Scales in lateral series 24–27 (24: 1, 25*: 3, 26: 3, 27: 3); transversal series 8–12 (8: 3; 9*: 3, 11: 1, 12: 1). Entire trunk covered by large scales; including breast, base of pectoral fin and sides of predorsal area where a narrow band of scales runs anteriorly from origin of D1 to above opercle. Single transversal row of scales directly in front of D1 ( Figs. 4 , 5 ). Otherwise predorsal area, nape, cheek and opercle naked; scales on trunk reach base of D2, but not base of D1, with narrow scaleless band on both sides of D1 that extends posteriorly to origin of D2.

Dentition. The premaxillary teeth arranged in an outer row of distinctly larger canine teeth and 5–6 inner rows of small conical teeth; on dentary some teeth of anteriormost row enlarged and caniniform, followed by series of 5– 6 intermediate rows of small conical teeth and an innermost row of enlarged teeth.

Gill-rakers (holotype). Seven short, stout gill-rakers on ceratobranchial bone, all of about same size; each gillraker with few (2–4) tiny denticles on its tip; no gill-rakers on epibranchial bone.

Vertebrae. Total number 28; 11 precaudal and 17 caudal, including urostyle.

Body proportions. Presented in table 2.

Head lateral line system ( Fig. 5 ). Anterior and posterior oculoscapular canals complete with pores (from anterior to posterior) B, C (unpaired), D (unpaired), E, F, G, H and K and L respectively. Preopercular canal with pores (from dorsal to ventral) M, N and O; these pores larger than pores of other head canals. Rows and number of neuromasts (sensory papillae) given in table 1. Generally, a high number of papillae in most neuromast rows.

Coloration (preserved in ethanol). Body pale fawn and brown; head, except nape, darker than trunk; lips not distinctly darker than head; neuromasts (sensory papillae) dark brown; margin of scale pockets dark brown, yielding a reticulated pattern. Two large brown blotches on flanks in lateral midline below center of first and of anterior half of second dorsal fin, respectively; no dark patches at bases of dorsal fins; brownish marking at origin of caudal fin faint; pectoral fin with distinct dark brown vertical band on its base, otherwise, like pelvic fins, uniformly dusky greyish; first dorsal and anal fins light dusky greyish; second dorsal fin with faint oblique stripes; caudal fin yellowish with 6–7 distinct dark vertical bands ( Fig. 6 ).

Etymology. From the Latin word laureatus meaning crowned with a laurel. The name refers to the shape of the scaled areas in the predorsal region.

Distribution and habitat. So far Thorogobius laureatus sp. nov. is only known from the type localities off Angola and from São Tomé and Príncipe, off the island of São Tomé. Specimens were dredged on upper slope of the continental shelf from 109– 57 m depth on soft bottom.

Remarks. Thorogobius laureatus sp. nov. differs distinctly from other species of the genus in the following specific characters (also see table 3 for an additional character matrix).

Thorogobius laureatus sp. nov. and Thorogobius alvheimi sp. nov. differ in: (1) squamation of nape and predorsal area (sides of nape and predorsal area scaled vs. naked) ( Figs. 3 , 5 , 7 ); (2) pattern of head neuromast lateral line system (distance between both rows half-length of row g or less vs. distance between rows g and h as least as long as row g; rows 6i and 6s opposite to each other vs. row 6i originates anterior to 6s); coloration (preserved) of (3) nape and predorsal area (no spots on nape and predorsal area vs. with pale spots in a reticulate pattern over dark ground laterally extending on dorsal part of opercle) ( Figs. 3 , 5 ); of (4) pectoral fin (dark band on base of pectoral fin vs. no dark vertical band on dorsal half of pectoral fin base) ( Figs. 2 , 4 , 6 ); of (5) caudal fin (with six to seven distinct dark vertical bands vs. uniformly dusky greyish) ( Figs. 2 , 6 ).

Thorogobius laureatus sp. nov. and Thorogobius angolensis differ in: (1) squamation of nape and predorsal area (only sides of nape and/or of predorsal area with narrow band of scales vs. predorsal area and nape completely covered with scales) ( Fig. 7 ); (2) squamation of opercle (no scales on dorsal part of opercle vs. scales on dorsal part of opercle); (3) scales in lateral midline (24–27 vs. 28–31); (4) gap between neuromast rows g and h (short vs. distinct); (5) number of neuromasts in head neuromast rows, e.g. neuromast row i1 (9–12 vs.19–25) and row i2 (9– 11 vs. 12–26); (6) length of row r2 (long, anteriorly passing row s3 and reaching upper lip vs. short, anteriorly not passing supraorbital row s2 and distant to upper lip); (7) coloration (preserved) of trunk (pale fawn to brownish with five brown blotches on flanks in lateral midline from below first dorsal fin to caudal peduncle vs. pale fawn to brownish with two brown blotches on flanks in lateral midline below rear of first dorsal and center of second dorsal fin); (8) dark vertical bands on caudal fin (6–7, first not more distinct than following bands vs. 6, first much darker than following); (9) dark blotch in pectoral fin (anteriorly on dorsal half of pectoral fin vs. pectoral fin uniformly dusky greyish).

Thorogobius laureatus sp. nov. and Thorogobius ephippiatus differ in: (1) scales in lateral midline (24–27 vs. 33–42); (2) lobe of pectoral fin and sides of nape and predorsal area (scaled vs. naked) ( Fig. 7 ); (3) neuromast rows tr and trp (present vs. absent); (4) neuromast rows g and h (long vs. short); (5) coloration (preserved) of body (uniformly brownish vs. covered with brown spots and blotches); (6) habitat preference (offshore between 57 and 165 m on soft bottom vs. inshore in 6–60 m on sandy areas of rocky shores, also cave dwelling); (7) distribution (off Angola and from São Tomé and Príncipe, off the island of São Tomé vs. Norwegian Sea to Canary Islands).

Thorogobius laureatus sp. nov. and Thorogobius macrolepis differ in: (1) number of pectoral fin rays (19–21 vs. 17–18); (2) lobe of pectoral fin and sides of nape and predorsal area (scaled vs. naked) ( Fig. 7 ); (3) number of neuromasts in head neuromast rows, e.g. r1 (11–19 vs. 5–8), r2 (9–23 vs. 4–8), 2 (13–20 vs. 7–12), 3 (15–22 vs. 8– 11), 4 (16–27 vs. 9–13), 5s (8–15 vs. 3–6), b (20–27 vs. 11–17), e1 (32–46 vs. 24–29), e2 (34–44 vs. 20–30), f (17– 31 vs. 10–15), as1 (14 vs. 7–11); (4) neuromast rows tr and trp (present vs. absent); (5) neuromast rows g and h (long vs. short); (6) coloration (preserved) of body (uniformly brownish vs. covered with pale spots and blotches); (7) habitat preference (offshore between 57 and 165 m on soft bottom vs. inshore in 6–60 m on sandy areas of rocky shores, also cave dwelling); (8) distribution (off Angola and from São Tomé and Príncipe, off the island of São Tomé vs. from the Mediterranean).

Thorogobius laureatus sp. nov. and Thorogobius rofeni differ in: (1) squamation of nape and predorsal area (sides of nape and predorsal area scaled vs. naked) ( Fig. 7 ); (2) scales in lateral midline (24–27 vs. 30–31); (3) neuromast rows tr and trp (present vs. absent); (4) number of neuromasts in head neuromast rows, e.g. r1 (11–19 vs. 5–8), r2 (9–23 vs. 5–8), m (7–13 vs. 4–8), h (20–31 vs. 12–17), as1 (14 vs. 10–13), la1 (8 vs. 5–7), la2 (6–8 vs. 4–5); (5) body deeper and wider (18.9–23.8% and 11.2–14.4% vs. 15.4–17.2% and 8.1–9.7% in SL); (6) caudal peduncle deeper (10.9–13.7% vs. 9.1–9.8% in SL); (7) upper jaw longer (41.8–58.0% vs. 33.0–37.2% in head length); (8) coloration (preserved) of trunk (two large brown blotches on flanks in lateral midline below center of first and of anterior half of second dorsal fin, respectively vs. no blotches).

Figures

FIGURE 1. Map of West Africa, showing sampling sites of Thorogobius angolensis (squares), Thorogobius alvheimi sp. nov. (circles), Thorogobius laureatus sp. nov. (triangles) and Thorogobius rofeni (diamonds).

FIGURE 2. Thorogobius alvheimi sp. nov. Holotype, CAS 222482, female, 72.1 mm SL; Angola. 15 April 2005. A dorsal view, B lateral view. Scale bar = 1 cm.

FIGURE 3. Thorogobius alvheimi sp. nov. Holotype. Detailed view of cephalic neuromast rows and spots on nape and predorsal area. Neuromast rows: s1, n, o, r1, r2, 1, 2, 3, 4, 5s, 5i, 6s, 6i, b, d, z, ot, oi, os, e2, i2, g, m, x1, x2, tr, trp, q, h, y. A dorsal view, B lateral view. Scale bar = 1 cm.

FIGURE 4. Thorogobius laureatus sp. nov. Holotype, CAS 243854, male, 65.1 mm SL; Angola. 22 April 2005. A dorsal view, B lateral view. Scale bar = 1 cm.

FIGURE 5. Thorogobius laureatus sp. nov. Holotype. Detailed view of cephalic neuromast rows and lateral bands of scales on nape and predorsal area. Neuromast rows: s1, n, o, r1, r2, 1, 2, 3, 4, 5s, 5i, 6s, 6i, b, d, z, ot, oi, os, e2, i2, g, m, x1, x2, tr, trp, q, h. A dorsal view, B lateral view. Scale bar = 1 cm.

FIGURE 6. Thorogobius laureatus sp. nov. Paratype, NMW 99080, male, 59.1 mm SL; São Tomé and Príncipe. 18 May 2010. Scale bar = 1 cm.

FIGURE 7. Sketch of the three different squamation patterns (dashed areas) in the predorsal area of the genus Thorogobius. Dorsal view of the head and anteriormost part of the body. A predorsal area without squamation (Thorogobius alvheimi sp. nov., Thorogobius ephippiatus, Thorogobius macrolepis, Thorogobius rofeni), B predorsal area with scaled lateral strips (Thorogobius laureatus sp. nov.), C predorsal area with complete squamation (Thorogobius angolensis).