Porogadus caboverdensis, Schwarzhans & Møller, 2021

Schwarzhans, Werner W. & Møller, Peter R., 2021, Revision of the ‘ dragon-head’ cusk eels of the genus Porogadus (Teleostei: Ophidiidae), with description of eight new species and one new genus, Zootaxa 5029 (1), pp. 1-96 : 28-29

Porogadus caboverdensis n. sp.

Figs. 9–10 , 44 , 49 , Tab. 1–7

Material examined ( 10 specimens): Holotype BMNH 1991.7 .9.826, 330 mm SL, 22°08’N 21°48’W ( Cape Verde Basin ), 4527–4630 m, R. R. S. Discovery Cruise, collected by N. Merrett, 02 September 1990; paratypes BMNH 1995.11.22.1-3 (3 specimens), 160–262 mm SL, 20°55’N 31°11’W ( Cape Verde Basin ), 4500–4610 m, R. R. S. Discovery Cruise semi-balloon otter trawl, collected by N. Merrett, 16 October 1993; BMNH 1995.11.22.12-14, 122– 290 mm SL, 20°53’N 31°13’W ( Cape Verde Basin ), 4480–4565 m, R. R. S. Discovery Cruise semi-balloon otter trawl, collected by N. Merrett, 4 October 1993; BMNH 1995.10 .31.9, 274 mm SL, 20°53’N 31°13’W ( Cape Verde Basin), 4000+ m (no depth recorded), R. R. S. Discovery Cruise semi-balloon otter trawl, collected by N. Merrett, 1 October 1993; BMNH 1998.8.9.9525-9526, 100+ and 225 mm SL, 20°08’N 24°49’W ( Cape Verde Plateau), 4500–4600 m, R. R. S. Discovery Cruise semi-balloon otter trawl, collected by N. Merrett, 24 September 1990.

Diagnosis. Precaudal vertebrae 17–18; long gill rakers on first gill arch 13–14; HL:HD 1.8–2.0; all head spines strong, present on ethmoidal, lacrimal, prefrontal, interorbital, supraorbital, sphenotic, 5th infraorbital, supratemporal, inner and outer posttemporal, inner preopercular rim, absent along outer preopercular rim; opercular spine sharp, strong, extruding; lower lateral line pores until beginning of anal fin 16–18; vomer with narrow dentition patch (1–3, rarely 4 rows of teeth); palatines with broad dentition patch (4–9 rows of teeth); otolith with single, uniform colliculum; OL:OH = 1.3–1.5 (1.05–1.2 in specimens <200 mm SL); OL:TCL = 2.1–2.45.

Description. Meristics: precaudal vertebrae 18 (17–18), 1 (1–2) last vertebrae without ribs; pectoral-fin rays 19 (17–20); D/V = 6 (5–6); D/A = 28 (25–28); V/A = 20 (18–20); long gill rakers 13 (13–14). Gill rakers on lower first gill arch with five plate-shaped rakers, followed by a series of 13 long rakers in holotype (13–14). The lower seven of those intercepted by single plate shaped rakers. Upper gill arch with a series of five plate shaped rakers intercepted by three slightly longer rakers.

Morphometrics: in % of SL: HL 15.7 (15.7–17.5); maximal HD 8.2 (8.2–9.3); HD through center of eye 5.5 (5.0–6.0); bony interorbital width 3.2 (3.0–3.5); snout length 5.6 (5.6–6.2); upper jaw length (9.5–10.7); predorsal 17.0 (17.0–19.8); preanal 30.0 (30.0–35.3); prepelvic 12.8 (12.8–14.7); prepectoral 15.7 (14.5–17.7); pectoral length 8.8 (8.8–11.8). Relations: HL:HD = 1.90 (1.79–1.98); HL to snout length 2.78 (2.74–2.96); preanal to predorsal 1.76 (1.61–1.80); predorsal to prepectoral 1.08 (1.06–1.12).

Slender fish with long tapering tail and long, pointed snout. Maximal size of fishes investigated 330 mm SL. Head long and slender, with straight or slightly convex dorsal profile, with strong spines as follows: ethmoidal (1), lacrimal (ridge with up to 4 spines), prefrontal (1), interorbital (2), supraorbital (1–2), sphenotic (3–4), 5th infraorbital (2–4), supratemporal (1), inner and outer posttemporal (4–5), inner preopercular rim (5, the upper 3 being the most prominent); no spines along outer preopercular rim. Opercle with sharp, strong, extruding spine. Eye moderately small located in strongly asymmetric orbit. Maxilla extending far beyond eye, strongly widened posteriorly and with distinct supramaxilla. Infra-/postorbital and mandibular-preopercular pores wide, several pores on occiput along inner edges of temporal and sphenotic spines. Head squamation on opercle, cheeks and occiput, rear portion of maxilla and in front of eyes and extending partly on snout. Opercle with three distinct large neuromasts behind preopercular edge; opercular flap large, with radial ridges along lower margin, rear part of opercle may be without scales. All three lateral line rows well visible. Upper lateral line row with 8–10 pores; lower lateral line row with 16–19 pores until beginning of anal fin; central lateral line row long, lower and central lateral line rows fading behind beginning of anal fin.

Dentition. All teeth tiny and cone-shaped. Vomer with a V-shaped dentition patch with 1–3 (rarely 4) rows of teeth anteriorly; palatines with a long and moderately wide dentition patch with 4–9 rows. Premaxilla tooth patches not fused anteriorly; ca. seven teeth rows anteriorly and 2–3 rows posteriorly. Dentary tooth patches not fused anteriorly; ca. five teeth rows anteriorly and 1–2 rows posteriorly. Median basibranchial tooth patch long and wide.

Otolith morphology (n = 7). Size up to 3.65 mm in length (holotype); OL:OH = 1.05–1.5, increasing with size (1.05–1.2 in specimens <200 mm SL, 1.3–1.5 in specimens> 200 mm SL); OH:OT = 2.4–3.6. Thin, oval, moderately elongate otolith, anteriorly rounded, posteriorly slightly pointed or rounded. Dorsal rim with obtuse predorsal angle; ventral rim regularly curving. All rims smooth. Inner face nearly flat, smooth, with short, centrally positioned sulcus; OL:TCL = 2.1–2.45. Sulcus with shallow, undivided, rather uniform colliculum showing ventral indentation towards posterior tip marking ostial-caudal joint. Dorsal field with broad, indistinct depression; ventral field with broad, half moon shaped ventral furrow. Outer face smooth, with moderate central umbo.

Coloration. Live coloration not known. Color of preserved specimens medium brown; head and belly darker than body, particularly opercle.

Discussion. Porogadus caboverdensis is a typical member of the Porogadus miles Group and resembles P. miles , P. longiceps , P. mendax n. sp., P. dracocephalus n. sp., and P. turgidus n. sp. in the long and slender head (HL:HD>1.75) and the many and intense spines on the head. It differs from P. miles , P. longiceps and P. mendax in the lower number of lower lateral line pores until the beginning of the anal fin (16–19 vs 21–26), the narrow dentition on the vomer (1–3 rows, rarely 4 vs 3–7 rows, rarely 2) and the compressed otolith (OL:OH = 1.05–1.5 vs 1.7–2.0, rarely 1.6). Porogadus caboverdensis differ from P. turgidus in the narrow vomer (1–3, rarely 4 rows of teeth vs 4–7 rows) and in the single, uniform colliculum in the sulcus (vs separated colliculi). From P. dracocephalus it differs in the wide palatines with 4–9 rows of teeth (vs 2–5 rows), the mostly higher preanal ratio (30.0–35.3 vs 28.6–30.6 % of SL) and the higher ratio OL:TCL of>2.1 (vs <2.0).

Distribution. Porogadus caboverdensis is a deep-water species that has only been caught below 4480 m in the Cape Verde Basin off northwestern Africa, where it occurs together with two other deep-water species, i.e., P.

Figures

FIGURE 9. Porogadus caboverdensis n. sp.; 9A, BMNH 1995.11.22.1, paratype, 160 mm SL 20°55’N, 31°11’W, 4500–4610 m; 9B, BMNH 1991.7.9.826, holotype, 330 mm SL, 22°08’N, 21°48’W, 4527–4630 m; 9C, BMNH 1998.8.9.9525, paratype, 225 mm SL, 20°08’N, 24°49’W, 4500–4600 m.

FIGURE 10. Porogadus caboverdensis n. sp.; 10A–B, BMNH 1991.7.9.826, holotype, 330 mm SL, 22°08’N, 21°48’W, 4527–4630 m, head drawings; 10C–E, BMNH 1995.11.22.3, paratype, 258 mm SL, 20°55’N, 31°11’W, 4500–4610 m, otolith (C anterior view, D inner face, E ventral view); 10F–G, BMNH 1991.7.9-826, holotype, 330 mm SL, 22°08’N, 21°48’W, 4527–4630 m, otolith (F inner face, G ventral view); 10H, BMNH 1995.11.22.12, 290 mm SL, 20°53’N, 31°13’W, 4480–4565 m, otolith; 10I–J, BMNH 1998.8.9.9525, 225 mm SL, 20°08’N, 24°49’W, 4500–4600 m, otolith (I inner face, J ventral view); 10K–L, BMNH 1995.11.22.13, 165 mm SL, 20°53’N, 31°13’W, 4480–4565 m, otolith (K inner face, L ventral view); 10M–N, BMNH 1995.11.22.14, 122 mm SL, 20°53’N, 31°13’W, 4480–4565 m, otolith (M inner face, N ventral view).

FIGURE 44. Geographic distribution of the species of the Porogadus miles group.

FIGURE 49. Depth versus distance from shelf plots for specimens of the Porogadus miles group (upper panel) and the Porogadus gracilis group (lower panel).