Phenacoscorpius eschmeyeri Parin and Mandrytsa, 1992

Motomura, Hiroyuki, Kanehira, Naoko & Imamura, Hisashi, 2012, Redescription of a Poorly Known Southeastern Pacific Scorpionfish (Scorpaenidae), Phenacoscorpius eschmeyeri Parin and Mandrytsa, Species Diversity 17 (2), pp. 145-150 : 146-149

Phenacoscorpius eschmeyeri Parin and Mandrytsa, 1992

[New English name: Eschmeyer’s No-line Scorpionfish]

( Fig. 1 ; Table 1)

Phenacoscorpius eschmeyeri Parin and Mandrytsa in Mandrytsa, 1992: 10, fig. 1 (type locality: Sala y Gomez Ridge, southeastern Pacific Ocean , 25°02′S, 90°41′W ).

Material examined. ZIN 49328, holotype, 132.8 mm SL, Sala y Gomez Ridge, 25°02′S, 90°41′W, 630 m depth, FRV Gerakl, 3 November 1975; HUMZ 164422, 124.0 mm SL, Nazca Ridge, 25°29′S, 90°19′W, 584 m depth, 24 October 1999; HUMZ 166546, 110.7 mm SL, Nazca Ridge, 25°31′S, 90°18′W, 580 m depth, 28 October 1999 .

Diagnosis. A species of Phenacoscorpius with the following combination of characters: pectoral fin rays 16–17, middle rays branched; pored lateral-line scales 2–7; palatine teeth present; second preopercular spine usually absent; nuchal and parietal spines fused to each other, forming single large spine; relatively long post-nuchal spine (11.0–11.3% SL), snout (11.6–12.4%), upper-jaw (22.3–23.8%), pre-dorsal-fin (43.7–44.0%), pre-anal-fin (75.2–80.6%), and prepelvic-fin (42.7–53.5%) lengths; relatively short spines and soft rays in dorsal, pelvic, and anal fins; 0–1 distinct black spots on posterior half of caudal peduncle; largest recorded specimen 133 mm SL.

Description. Morphometrics and selected meristics of P. eschmeyeri given in Table 1. Body moderately compressed from side to side anteriorly, progressively more compressed posteriorly. Nape and anterior body moderately arched. Body moderately deep, but body depth less than head length. Uppermost ray and lower 9 rays of pectoral fin unbranched, remaining rays branched; ninth or tenth ray longest. Second soft rays longest among pelvic and anal fin rays. No distinct papillae, tentacles, or cirri on head and body. No supraocular tentacles. No fimbriate flap on posterior lacrimal spine. Pectoral fin axil without skin flap. Cycloid scales covering opercle, cheek, and area defined by orbit, suborbital ridge, upper preopercle, nuchal spine, and lower posttemporal spine. Ctenoid scales (some scales cycloid) covering interorbital and occiput region; scales becoming smaller anteriorly; other parts of head not covered with scales. Wellexposed ctenoid scales covering lateral surface of upper body, scales becoming cycloid ventrally. Body scales not extending onto rays or membranes of fins, except basal part of caudal fin. Exposed cycloid scales covering anteroventral surface of body and pectoral fin bases. Embedded cycloid scales covering area between first anal-fin spine base and anus. Lateral line incomplete; last pored lateral-line scale below spinous portion of dorsal fin.

Mouth large, slightly oblique, forming angle of about 20 degrees to longitudinal axis of head and body. Posterior margin of maxilla just reaching to a vertical drawn through posterior margin of orbit. Lateral surface of maxilla smooth, without ridges, tentacles, or scales. Lower jaw with symphyseal knob. Width of symphyseal gap separating premaxillary teeth bands subequal to width of each band. Upper and lower jaw each with band of villiform teeth, tooth band of upper jaw wider than that of lower jaw, lengths of most teeth in both jaws equal. Vomer and palatines with villiform teeth; width of vomer plate subequal to length of palatine plate. Underside of dentary with 3 sensory pores on each side, first pore below tip of anterior lacrimal ridge, second pore below a point between anterior and posterior lacrimal spines, third pore located on posterior margin of dentary. A pore behind symphyseal knob of lower jaw on each side. Underside of lower jaw smooth, without ridges or tentacles.

Dorsal profile of snout steep, forming an angle of about 50 degrees to longitudinal axis of head and body. Nasal spine simple, somewhat conical, directed upward. Anterior nostril with low membranous tube and no tentacle. Ascending process of premaxilla not intruding into interorbital space, its posterior margin not extending beyond level of posterior margin of posterior nostril. Median interorbital ridge absent. Interorbital ridges poorly developed, separated by shallow channel, beginning posterior to nasal spines and not conjoined to each other. No distinct ridge on anterior edge of occiput. Interorbital ridges diverging anteriorly and posteriorly in dorsal view, space between interorbital ridges narrowest at a vertical through anterior margin of pupil. Interorbital space shallow, only about one-tenth of orbit extending above dorsal profile of head. Preocular spine simple, directed nearly upward. Supraocular spine simple, its tip located above middle of eye. Postocular spine simple, slightly shorter than tympanic spine. Tympanic spine simple; bases of tympanic spines joined with interorbital ridges. Coronal, interorbital, and pretympanic spines absent. Occiput nearly flat. No distinct transverse ridge at rear of occiput. Occiput surrounded laterally by tympanic and nuchal spines. Nuchal and parietal spines fused to each other, forming single large spine. Sphenotic with small spines. Postorbital smooth. Pterotic spine simple. Upper posttemporal spine absent, but distinct ridge present. Lower posttemporal spine simple, its base longer than that of pterotic spine. Supracleithral and cleithral spines flattened, rounded, lacking pointed tips.

Single lateral lacrimal spine present but small (absent in smaller specimen). Anterior lacrimal spine indistinct, not pointed; no additional spines at anterior base of lacrimal spine. Posterior lacrimal spine simple, not strongly pointed, triangular, its tip not reaching upper-jaw lip. Posterior lacrimal spine larger than anterior spine. Suborbital ridge with 4–6 spines, first spine below middle of eye. Preopercle with 4 or 5 spines, uppermost spine largest with supplemental preopercular spine on its base, second spine small or absent, third to fifth spines without median ridge. Preopercle without serrae or spines between uppermost preopercular spine and its own upper end. Upper opercular spine simple, without median ridge. Lower opercular spine simple, with distinct median ridge. Space between upper and lower opercular spines not covered with fleshy skin. Posterior tips of upper and lower opercular spines not reaching opercular margin.

Origin of first dorsal-fin spine above first pored lateralline scale. Posterior margin of opercular membrane extending beyond vertical drawn through origin of second dorsal-fin spine. Posterior tip of pectoral fin reaching vertical drawn through middle of soft-rayed portion of dorsal fin. Posterior tip of depressed pelvic fin not reaching to anus. Origin of pelvic fin spine anterior to origin of pectoral fin. Origin of first anal-fin spine slightly posterior to origin of last dorsal-fin spine.

Color when fresh ( Fig. 1B ). Body and fins pale reddish, mottled with whitish blotches, without black stripes, bands, or blotches. Dark areas faintly seen through opercle and abdomen. Color when alive unknown.

Color of preserved specimens ( Fig. 1C ). Body uniformly white, except for black eyes and spot on caudal peduncle. No black blotch on spinous portion of dorsal fin.

Remarks. Phenacoscorpius eschmeyeri and P. adenensis can be easily distinguished from their congeners in the Indo–Pacific by having teeth on the palatines (Motomura 2008; Motomura and Last 2009). Parin and Mandrytsa in Mandrytsa (1992) separated P. eschmeyeri from P. adenensis by its having 16 pectoral fin rays (vs 17 rays in the latter) and six anal fin soft rays (vs five rays). However, the newly collected specimens of P. eschmeyeri have 17 pectoral fin rays on both sides of the body and five anal fin soft rays ( Table 1); no other morphological difference between the holotype and the new specimens was found. In fact, the number of anal fin soft rays of the holotype (six) is unusual in the Scorpaenidae , species of which usually have five rays if there are three spines in the anal fin (six rays if two spines) and is most likely to be a deformity. The number of pectoral fin rays in some species of Scorpaenidae , including Phenacoscorpius , has a range of variation; e.g., Phenacoscorpius megalops Fowler, 1938 has 16–18 rays (Motomura 2008). Thus, the two characters, i.e., numbers of pectoral and anal fin rays, given by Parin and Mandrytsa in Mandrytsa (1992) cannot be used to separate the two species.

Examination of the holotype and the two new specimens showed that the nuchal and parietal spines of the specimens are fused to each other, forming a single large spine. This is a unique character among the species of Phenacoscorpius ; the nuchal and parietal spines of other congeners are indeed basally fused, but still present as two distinct spines (Motomura 2008; Motomura and Last 2009; Motomura et al. 2012). In Scorpaeninae , such a condition of the spine as found in P. eschmeyeri is known only in the western Indian Ocean species Neoscorpaena nielseni (Smith, 1964) , and is regarded as a diagnostic character for the monotypic genus Neoscorpaena Mandrytsa, 2001 ( Eschmeyer 1986; Motomura et al. 2011a).

In addition to the nuchal spine character, a detailed comparison of P. eschmeyeri with P. adenensis revealed that the post-nuchal-spine length of P. eschmeyeri (11.0–11.3% of SL) is greater than that of P. adenensis (3.2–9.5% of SL; Motomura et al. 2012: table 1). Lengths associated with the post-nuchal-spine length, i.e., pre-dorsal-fin (mean 43.8% of SL), pre-anal-fin (77.0%), and pre-pelvic-fin (46.7%) lengths, of P. eschmeyeri are also greater than those (40.1%, 68.5%, and 38.4% respectively) of P. adenensis (see range of values in Motomura et al. 2012: table 1). Furthermore, the unpaired fins, i.e., the spines and soft rays of the dorsal, pelvic, and anal fins, of P. eschmeyeri are extremely short compared with those of P. adenensis ; for example, third dorsal-fin spine length 10.5–11.5% of SL in P. eschmeyeri vs 16.3–20.7% in P. adenensis (see Table 1; Motomura et al. 2012: table 1). Moreover, P. eschmeyeri tends to have a relatively longer snout (11.6–12.4% of SL) and upper jaw (22.3– 23.8%) than P. adenensis (9.4–12.0% and 19.4–22.6% respectively), although there is a slight overlap between the two species. The examined specimens of P. eschmeyeri (110.7– 132.8 mm SL) are larger than those of the small species P. adenensis (17.8–79.4 mm SL); proportions vary ontogenetically in most scorpaenids, and these apparent morphometric differences might disappear when smaller specimens of P. eschmeyeri that are of comparable size to P. adenensis are examined.

Figures

Fig. 1. Photographs of Phenacoscorpius eschmeyeri. A, ZIN 49328, holotype, 132.8mm standard length; B, fresh specimen, HUMZ 164422, 124.0mm standard length; C, preserved specimen, same as B.