Pseudoscopelus altipinnis Parr 1933

Melo, Marcelo R. S., 2019, A revision of the genus Pseudoscopelus Lütken (Chiasmodontidae: Acanthomorphata) with descriptions of three new species 2710, Zootaxa 2710 (1), pp. 1-78 : 36-42

Pseudoscopelus altipinnis Parr 1933

Figures 15 A–B , 16 A , 17 A , 18 A , 28 G; Table 6.

Pseudoscopelus altipinnis Parr 1933: 41–42 , figure 18 [type locality western Central Atlantic, off Cat Island, Bahamas, 24º51’ N, 76º28’ W, holotype YPM 2798, 185.8 mm]; Lavenberg 1974: 261–273, figures 52, 53, 58 [North Atlantic, Indo-Pacific, Central Pacific]; Uyeno et al. 1983: 403 [western Central Atlantic, off Suriname, with brief description and picture, questionable]; Figueiredo et al. 2003: 94 [literature compilation]; Prokofiev and Kukuev 2006a [key to species, questionable]; 2006c [in key]; 2008, figures 8, 9, 24, 25, 30, 31, 33, 51, 52, 62, 73, 75, 87–98, table 2 [Atlantic, western Indian and western Pacific; species account and key to species].

Pseudoscopelus microps Fowler 1934: 359 , figure 110 [type locality Gulf of Boni, Sulawesi, Indonesia, holotype USNM 93139, 122.7 mm]; de Beaufort in de Beaufort and Chapman 1951: 8–9 [western Central Pacific].

Pseudoscopelus microps (non Fowler 1933), Prokofiev and Kukuev 2005; Prokofiev and Kukuev 2006a: 212–218, figure 1, table 1.

Pseudoscopelus scriptus (non Lütken 1892), Norman 1929: 543–544, figure 11.

Diagnosis. A species of the Pseudoscopelus altipinnis species group, which can be distinguished from P. paxtoni by dentition and photophore pattern: innermost premaxillary teeth in mesial row not extremely elongated, when mouth is closed teeth not reaching the contralateral premaxilla (vs. innermost premaxillary teeth in mesial row very elongate, reaching contralateral premaxilla when mouth is closed); teeth of mesial row of premaxilla and internalmost row of dentary slightly curved (vs. teeth of mesial rows of premaxilla and internalmost row of dentary straight); mesial series of premaxillary teeth arranged in transverse rows of one to five rows of teeth (vs. mesial series of premaxillary teeth arranged in transverse rows of one to three rows of teeth).

Description. Large-sized species of Pseudoscopelus , largest specimen examined 188.3 mm SL. Morphometric data summarized in Table 6. General body shape as described for genus with diagnostic characteristics of species and species group.

First dorsal-fin rays vii (5), viii (14), ix (6*); second dorsal-fin rays ii+21 (3), ii+22 (11), ii+23 (10), iv+21 (1*); anal-fin rays iii+20 (1), iii+21 (4), iii+22 (16), iii+23 (1), iii+24 (1), iv+20 (1*), iv+22 (1); pectoral-fin rays 12 (7*), 13 (15), 14 (3); pelvic-fin rays I+5 (25*); caudal-fin rays i+7+8+i (22*), i+8+7+i (3). Branchiostegal rays 7 (24*), 8 (1). Pre-caudal vertebrae 16 (2), 17 (7), 18 (7); total vertebrae 36 (2), 37 (12), 38 (4).

Lateral line complete; lateral-line pores 75 (1), 76 (3), 77 (5), 78 (6), 79 (6), 80 (3*), 81 (1). Pores in temporal canal 2 (25*); supratemporal canal 3 (25*); otic canal 2 (25*); supraorbital canal 5 (3), 6 (22*); supranasal pore 1 (1), 2 (22*), 3 (2); epiphyseal branch 3 (25*); infraorbital canal 12 (25*); preopercular canal 5 (25*); mandibular canal 6 (25*); fifth pore of mandibular canal 1 (23*), 2 (2).

Dentition. Enlarged teeth on premaxilla, dentary and palatine. Premaxilla and dentary illustrated in Figure 16 A . Premaxilla moderately wide, widest point of premaxillary body 15–20 % in premaxillary length.

Premaxillary teeth on head, neck, body and caudal process. Lateral series of teeth in single longitudinal row, along lateral edge of premaxillary head, neck, body and caudal process; teeth slightly curved; posterior two teeth on caudal process considerable thicker than anterior, type 1. Canine and fang on ventral shelf of premaxillary head. Middle and mesial series on ventral shelf of premaxillary body. Middle series in three irregular rows; teeth needle-like, straight, gradually increasing in size from lateral to medial. Mesial series in transverse rows, each row with three to five teeth; teeth needle-like but not long enough to reach contralateral premaxilla, as in Pseudoscopelus paxtoni , slightly curved, gradually increasing in size from medial to mesial. Dentary teeth in lateral and mesial series. Lateral series along lateral shelf of dentary, in single, longitudinal row, extending from symphysis to posterior tip; teeth conical, slightly curved. Mesial series on dorsal shelf of dentary, in transverse rows of one to four teeth; teeth straight, needle-like, increasing in size from lateral to mesial. Palatine teeth 3 (2*), 5 (3), 6 (8), 7 (3), 8 (8), 10 (1); in single, longitudinal row.

Teeth on infrapharyngobranchials and fifth ceratobranchial, conical, curved. Teeth on second basibranchial 7 (1), 8 (1), 9 (4), 10 (4), 11 (3), 12 (3), 13 (5*), 14 (3), 15 (1), conical, in V -shaped or two rows. Teeth absent on basihyal and other basibranchials. Gill rakers on first epibranchial 0 (14*), 1 (11); first ceratobranchial 7 (3), 8 (5), 9 (8), 10 (5*), 11 (4); first hypobranchial 3 (2), 4 (1), 5 (6), 6 (9), 7 (6*), 8 (1). Gill rakers absent on other elements.

Luminescent organs. Luminescent organs present as discrete photophores on head and body ( Fig. 17 A ). Photophores on head: dnf, inof 1–2, lpf, opf, and pof absent; mxf elongated, in single irregular row with widely spaced photophores, parallel to maxilla, from below mid-eye and connected to apf posteriorly; apf at angle between dentary and preopercle; vnf as triangular patch posterior to anteriormost supraorbital pore; ppf usually present as small patch of one to four photophores in ventral edge of interopercle (in BMNH 1961.1.30.7, and ZMUC P. 6542 present as single organ on one side); amf in two to three rows, medial to and around third pore of mandibular canal; pmf in one to three rows, lateral to mandibular canal, from fourth pore to halfway between fifth and sixth pores.

Photophores on body: lvf, rtf, spf and svf absent; pf extending to halfway of pectoral-fin length, in ventral ray; paf continuous with pf, at pectoral-fin axil; vf in single row, along mesial pelvic-fin ray; vaf triangular, continuous with vf and trf, not extending over base of pelvic rays three to five; if in one irregular to two rows, from isthmus to ventral edge of cleithrum, prvf in irregular one to two rows, in anterior part of pelvic girdle; ptvf in two rows, from posterior half of pelvic fin to close to anus; trf in single irregular row with widely spaced photophores; saf in single row, heart-shaped, extending anteriorly to level of anus, and connected posteriorly immediately after last anal-fin ray; prcf in posterior half of peduncle, tri-pronged, medial prong extending over lower procurrent rays, and lateral prongs extending lateral to lower procurrent rays; scf usually absent, but present in few specimens from single photophore to linear irregular row of four photophores.

Color. Most specimens examined faded to light brown or bleached white; holotype partially bleached, with brown belly and pale yellow in the head, dorsum, caudal peduncle, and fins. Body uniformly black or dark brown, except for triangular area on epiphyseal branch. Pectoral, pelvic, first and second dorsal fins, and anal fin slightly pigmented; caudal fin pigmented. Internal part of mouth and gill arches black, including skin on toothed area of premaxilla and dentary, over basihyal and basibranchials, roof, floor and lateral wall of mouth, internal part of opercle, membrane between dentaries and premaxillae, and gill arches; gill filaments pale.

Distribution. Widespread in the Atlantic and Pacific Oceans; in the Atlantic Ocean from 46º N to 36º S, 7º W to 88º W; in the Pacific Ocean from 33º N to 27º S, 99º W to 121º E ( Fig. 18 A ). Prokofiev and Kukuev (2008, figure 98) presents several records from the western Indian, but only a single lot appears in the material examined (ZM MGU 21247), and one lot was reported from the western North Pacific, off Japan PINRO ZN 53031). M. Okamoto (persn. comm. May, 2010) confirmed the existence of the species in Japanese waters.

Bathymetric distribution. Meso- to bathypelagic, most records from 50 to 1870 (mean 828 m); a single lot from deeper than 2000 meters ( UF 148739, 4631 m) .

Identification of juveniles. The smallest specimen recognized has 23.6 mm (USNM 288992); the identification was tentatively made based on the photophore pattern and pigmentation of mouth. The smallest specimen with photophores and dentition fully developed has 38.5 mm (USNM 288991); with the exception that trf and mxf are closely spaced.

Remarks. The photophore group scf was found exclusively, and in almost every specimen of Pseudoscopelus altipinnis from the western North and South Atlantic (e.g., BMNH 1961.1.30.7, MCZ 96843, ZMUC P. 6540); however, it was not present in all specimens within that range (e.g., BMNH 1930.1.12.1065; ZMUC P. 6546). The presence of scf may be an indication of isolation of the western Atlantic populations, but because no other characteristic was found to diagnose them as a separate species, this characteristic is being interpreted as a geographical variation.

Prokofiev and Kukuev (2005, 2006a) diagnosis of P. altipinnis , Pseudoscopelus cf. altipinnis and P. microps were erroneous. Corrections were made in their most recent works ( Prokofiev and Kukuev 2006c, 2008) with the description of P. astronesthidens in place of P. altipinnis ; P. australis in place of Pseudoscopelus cf. altipinnis , and the recognition of P. altipinnis in place of P. microps .

Figures

FIGURE 15. Pseudoscopelus altipinnis: (A) YPM 2798, 185.8 mm, holotype; (B) USNM 93139, 122.7 mm, holotype of P.microps.

FIGURE 16. Schematic drawing of dentition pattern in the species of Pseudoscopelus: (A) P. altipinnis, ZMUC P. 6546, 111.8 mm; (B) P.paxtoni, NMNZ P. 38679, 234.2 mm, paratype; (C) P. scutatus, ISH 647a-1966, 83.4 mm, paratype; (D) P. odontoglossum, SIO 61-48, 70.2 mm, holotype. Premaxilla (above) and dentary (below); bones with complete dentition are represented on top, and bones with only the sites for teeth attachment on bottom; circes are proportional to diameter of tooth-base; scale bar equals 10.0 mm; C stands for canine and F, for fang.

FIGURE 17. Schematic drawing of the photophore pattern in lateral and ventral views of (A) Pseudoscopelus altipinnis, YPM 2798, 185.8 mm, holotype; (B) P. paxtoni, MNMZ P. 37858, 200.4 mm, paratype. Dashed lines indicate level of anus.

FIGURE 18. Maps of distribution of (A) Pseudoscopelus altipinnis (triangle) and P.paxtoni (star); (B) P. scutatus (star) and P. bothrorrhinos (diamond). Each symbol may represent more than one locality; solid symbols represent type localities.