Porogadus lacrimatus, 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 : 52-53

Porogadus lacrimatus n. sp.

Figs. 23–24 , 45 , 50 , Tab. 1–7

Material examined ( 3 specimens): Holotype ZMUC P 77845, 204 mm SL, BIOCAL exp. Sta. 05, off New Caledonia, 21°16’S 166°43’E, 2340 m, 11 August 1985; paratypes BSKU 82357, 194 mm SL and BSKU 82358, 161 mm SL, 01°59’S 157°12’E, 1610 m, R / V Hakuho-maru , 3 m beam trawl, 9 Feb. 1990.

Diagnosis. Precaudal vertebrae 16; long gill rakers on first gill arch 18–20; HL:HD 1.52–1.59; moderately strong head spines: on ethmoidal, prefrontal, interorbital, supraorbital, sphenotic, supratemporal, inner and outer posttemporal, weak along inner preopercular rim, on lacrimal with ridge, absent on outer preopercular rim and 5th infraorbital; opercular spine sharp, extruding; maxilla without scales; small opercular flap; lower lateral line pores until beginning of anal fin 18; vomer with narrow dentition patch with few teeth; palatines with moderately broad dentition patch (3–4 rows of teeth); otolith with single colliculum; OL:OH = 1.44; OL:TCL = 2.37.

Description. Meristics: precaudal vertebrae 16, 2 (1–2) last vertebrae without ribs; pectoral-fin rays 16 (16– 17); D/V = 5 (5–6); D/A = 21 (21–24); V/A = 16 (16–17); long gill rakers 19–20 (18–20). Gill rakers in holotype on lower first gill arch with four short rakers, followed by a series of 20 long rakers. The lower seven of those intercept by short rakers. These are smaller than in most species and placed on the inner part of the gill arch. Upper gill arch with a series of six very short rakers and four semi long rakers intercepted.

Morphometrics: in % of SL: HL 14.9 (13.7–14.0); maximal HD 9.3 (8.7–9.6); HD through center of eye 6.7 (6.4–6.7); bony interorbital width 3.8 (3.1–3.8); snout length 4.6 (4.4–4.6); upper jaw length 9.3 (8.6–9.3); predorsal 16.3 (15.4–16.3); preanal 28.7 (26.7–28.7); prepelvic 12.2 (11.3–12.2); prepectoral 15.5 (14.1–15.2); pectoral length no measurable. Relations: HL:HD = 1.59 (1.52–1.59); HL to snout length 3.26 (3.03–3.34); preanal to predorsal 1.76 (1.73–1.76); predorsal to prepectoral 1.05 (1.05–1.10).

Slender fish with long tapering tail and short, rounded snout. Maximal size of fishes investigated 204 mm SL. Head relatively short and compact, with flat to slightly convex dorsal profile, with strong spines and ridges as follows: ethmoidal (1), prefrontal (1), interorbital (2–3), supraorbital (1–2), sphenotic (2), supratemporal (2), inner and outer posttemporal (2–3); weak spines as follows: inner preopercular rim (2–4), lacrimal (1 short ridge); no spines along outer preopercular rim and on 5th infraorbital. Opercle with sharp, extruding spine. Eye moderately large, located in strongly asymmetric orbit. Maxilla extending far beyond eye, strongly widened posteriorly and with distinct supramaxilla. Infra-/postorbital and mandibular-preopercular pores wide, head top with cavernous system extending between occiput and sphenotic and supraorbital spines, sometimes opening in up to 4 bilateral symmetrical openings (pores or damaged thin skin cover?). Head squamation on opercle, and cheeks, absent on maxilla, occiput, frontal, and around eyes. Opercle with two moderately sized neuromasts behind preopercular edge; opercular flap small. Lateral line rows rarely well visible and therefore number of pores countable only in rare instances. Lower lateral line row with 18 pores until beginning of anal fin in one specimen.

Dentition.All teeth tiny and cone-shaped. Vomer without or with only few teeth anteriorly and with a single row posteriorly; palatines with a short and narrow dentition patch with 3–4 rows of teeth in middle part. Premaxilla tooth patches narrow, not fused anteriorly; ca. 3 teeth rows anteriorly and 1–2 rows posteriorly. Dentary tooth patches not fused anteriorly; ca. 5 teeth rows anteriorly and 2 rows posteriorly. Median basibranchial tooth patch short.

Otolith morphology (n = 1; holotype). Size 3.6 mm in length; OL:OH = 1.44; OH:OT = 2.8. Relatively thin and moderately elongate otoliths with tear-drop shape, anteriorly broadly rounded, posteriorly slightly expanded and pointed. Dorsal rim with broad, rounded predorsal lobe, ventral rim regularly curved. All rims smooth. Inner face nearly flat, smooth, with short, centrally positioned sulcus; OL:TCL = 2.37. Sulcus shallow, undivided, with broad and shallow colliculum. Dorsal field with indistinct depression; ventral field smooth, with faint ventral furrow anteriorly joining ventral rim of otolith below anterior part of sulcus. Outer face smooth, with mild, anteriorly positioned umbo.

Coloration. Live coloration not known. Color of preserved specimens light to medium brown throughout except for dark opercle.

Discussion. Porogadus lacrimatus differs from other members of the Porogadus trichiurus group in the short and compact head (HL:HD = 1.52–1.59 vs 1.71–1.81) and the head being more light colored (in preserved specimens) than in the other species.

Distribution. Porogadus lacrimatus is known from few specimens from the tropical West-Pacific from the Solomon and New Hebrides seas, where it occurs at moderate depth between 1600 and 2340 m and apparently can venture out from the shelf break for a considerable distance to about 500 km.

Etymology. From lacrima (Latin) = tear, referring to the tear-drop shape of the otolith.

Figures

FIGURE 23. Porogadus lacrimatus n. sp., ZMUC P77845, holotype, 204 mm SL, 21°16’S, 166°43’E, 2340 m, (A–B photography, C x-ray photograph).

FIGURE 24. Porogadus lacrimatus n. sp.; 24A–B, ZMUC P77845, holotype, 204 mm SL, 21°16’S, 166°43’E, 2340 m, head drawing; 24C–D, BSKU 82358, paratype, 161 mm SL, 01°59’S, 157°12’E, 1610 m; 24E–F, ZMUC P77845, holotype, 204 mm SL, 21°16’S, 166°43’E, 2340 m, otolith (E inner face, F ventral view).

FIGURE 45. Geographic distribution of the species of the Porogadus trichiurus group.

FIGURE 50. Depth versus distance from shelf plots for specimens of the Porogadus trichiurus group (upper panel) and the Porogadus catena group (lower panel).