Pteroidichthys acutus, Motomura, Hiroyuki & Kanade, Yuka, 2015

Motomura, Hiroyuki & Kanade, Yuka, 2015, Review of the scorpionfish genus Pteroidichthys (Scorpaenidae), with descriptions of two new species, Zootaxa 4057 (4), pp. 490-510 : 495-498

Pteroidichthys acutus n. sp.

[New English name: Longsnout Weedy Scorpionfish] ( Figures 1 C–D, 3B, 4–6; Table 2 )

Holotype. MNHN 2001-2851, 38.7 mm SL, south of Vele, Wallis and Futuna Is., 14°19′05ʺS, 178°04′05ʺW, 245– 400 m, RV Alis, 11 May 1992.

Paratypes. 6 specimens, 35.4–40.8 mm SL. Philippines: ASIZP 68097, 36.6 mm SL, Dingalan, Aurora, 15°20′34ʺN, 121°29′46ʺE, Y.-C. Liao and K.-T. Shao, 8 May 2007; MNHN 2010-0535, 36.7 mm SL, northwest of Tungao Bay, Caluya, 12°07′59ʺN, 121°16′59ʺE, 73–84 m, RV Alis, 3 June 1985. Vanuatu: KAUM –I. 71525, 40.8 mm SL, Tutuba, Sanma, 15°36′00′S, 167°16′01ʺE, 182–215 m, RV Alis, 5 Oct. 1994; MNHN 1998-0229, 35.5 mm SL, Aneityum Is., Tafea, 20°19′01ʺS, 169°52′59ʺE, 250–315 m, RV Alis, 21 Sept. 1994; MNHN 1998-0760, 35.4 mm SL, Malo, 15°40′12ʺS, 167°18′00″E, 155–161 m, RV Alis, 5 Oct. 1994; MNHN 2002-0030, 34.9 mm SL, northwest of Abnetare, Malo, 15°37′59ʺS, 167°03′00″E, 140–175 m, RV Alis, 11 Oct. 1994.

Diagnosis. A species of Pteroidichthys with the following combination of characters: anal fin with 3 spines and 5 soft rays; dorsal-fin spines rigid; snout relatively long, its length 18.0–21.2% (mean 19.6%) of SL, longer than postorbital length; posterior margin of maxilla just reaching to or short of vertical through anterior margin of pupil; distance between tips of lateral lacrimal and first suborbital spines longer than that between tips of first and second suborbital spines; supplemental preopercular spine present; tentacles on supraocular and posterior lacrimal spines poorly developed, their lengths less than orbit diameter; few tentacles on trunk and fins; lateral lacrimal and suborbital spines well developed, with pointed tips; membranes between last spine and fourth soft ray of dorsal fin with large black blotch.

Description. Meristics and morphometrics of holotype and paratypes of P. acutus are shown in Table 1. Data for the holotype are presented first, followed by paratype data in parentheses (if different). Characters given in the diagnosis of the species are not repeated here.

Fifth dorsal-fin spine longest, its length less than upper-jaw length; fifth to eleventh spines progressively shorter; penultimate (= eleventh) spine shortest, its length less than half of length of last spine; distal margin of spinous portion of dorsal fin moderately notched; membrane of spinous portion of dorsal fin not fleshy. First soft ray and posterior branch of last soft ray of dorsal fin, divided into 2 at base, unbranched; remaining rays branched; posterior branch of last soft ray shortest, joined by membrane to caudal peduncle for less than one-third its length; tip of depressed posterior branch of last soft ray extending beyond vertical through posterior margin of hypural plate. Third anal-fin spine longest, its length less than second dorsal-fin spine length. First anal-fin soft ray unbranched; remaining rays, including posterior branch of last ray, branched; posterior branch of last soft ray shortest, not joined by membrane to caudal peduncle; tip of depressed posterior branch of last soft ray extending beyond (or just short of) a vertical through posterior margin of hypural plate; membranes between rays weakly notched. All pectoral-fin rays unbranched (tips of fifth to seventh rays branched); eighth ray longest, its length less than head length; membranes between upper rays weakly notched; membranes between lower rays strongly notched. Pelvic-fin spine length subequal to length of third anal-fin spine. First to fourth soft rays of pelvic fin branched, fifth ray unbranched (or all rays branched); third or fourth ray longest, less than upper-jaw length; last soft ray joined by membrane to abdomen for more than two-thirds its length; membranes between rays weakly notched. Gill rakers short and spinous, longest raker on first gill arch less than half length of longest gill filament; fourth gill slit closed by membrane. Vertebrae 24. Swimbladder absent.

Holotype Paratypes

MNHN 2001-2851 n = 6

Body and head strongly compressed; body width less than length of longest dorsal-fin spine. Body shallow, deepest at bases of first to third dorsal-fin spines. Head large, its length greater than body depth. Ventral surface of posterior lacrimal spine with unbranched, slender tentacle, its length less than depth of posterior margin of maxilla; tip of tentacle not reaching to posterior margin of maxilla when laid back. Slender tentacle on posterior margin of low fleshy rim associated with anterior nostril, extending beyond anterior margin of posterior nostril, but not reaching anterior margin of orbit when laid back. Supraocular tentacle well-developed, fleshy, its margin corrugated, its length variable, but always longest in other tentacles on head. Three pairs (rarely one pair) of short tentacles on lower surface of lower jaw; first located beside symphysial knob, its length subequal to length of posterior lacrimal spine tentacle; second and third tentacles present (rarely absent) on dentary. Small elliptical or circular fleshy tentacles on outer part of eye membrane. Few tentacles on lateral surface of body. Pectoral-fin axil without skin flaps.

Posterior nostril opening upward behind upper lacrimal ridge, not visible laterally. No distinct sensory pores around anterior and posterior nostrils. Underside of dentary with 3 small sensory pores on each side. Small pore behind nodular portion of lower jaw on each side. Body scales cycloid. Well-exposed scales covering an area surrounded by opercular margin and tips of upper and lower opercular spines; other parts of head not covered with exposed scales. Well-exposed scales on lateral surface of body; body scales not extending onto rays or membranes of median fins, except on caudal-fin base. Exposed scales covering pectoral-fin base and ventral surface of body, including between pelvic fins; no scales embedded by skin. Lateral line sloping downward at tip of opercle.

Mouth oblique, forming angle of about 20˚ to horizontal axis of head and body. Upper edge of posterior maxilla slightly swollen laterally, forming indistinct ridge; central part of maxilla nearly flat (or slightly convex) with median ridge. Lower jaw with thickened symphysial portion fitting into shallow median depression of upper jaw when mouth fully closed. Width of symphysial gap separating premaxillary teeth bands slightly greater than (or approximately equal to) width of each band. Upper jaw with band of slender, conical teeth, tips of teeth strongly pointed. Two tooth rows at front of upper jaw, tooth band narrowing posteriorly. Tooth band of upper jaw slightly wider than that of lower jaw. Lower jaw with band of slender, conical teeth. No (or few) teeth at front of vomer, 2 or 3 rows posteriorly, forming a V-shaped patch on vomer. No teeth on palatine. Underside of lower jaw with indistinct, low longitudinal ridge centrally.

Dorsal profile of snout curved sinuously, initially convex, then deeply concave. Nasal spine with 2 spinous points, directed dorsally, its tip well exposed. Posterior margin of ascending process of premaxilla not extending beyond vertical through posterior margin of posterior nostril. Interorbital ridges present, but poorly developed; beginning slightly anterior to base of supraocular tentacle and ending at posterior end of postocular bone base. Interorbital space deep, U-shaped in transverse section at level of mid-orbit; about one-third (to three-fifths) of orbit extending above dorsal profile of head. Preocular spine simple, directed dorsoposteriorly; its anterior surface with indistinct longitudinal median ridge; tip extending beyond horizontal line through upper margin of pupil in lateral view. Supraocular and postocular spines joined at base to each other; postocular spine with 2 points in left side of head, simple in right side (with 1–3 spinous points). Tympanic spine tiny, its length shorter than nasal spine. No interorbital, coronal, pretympanic spines. Occipital pit moderately deep with distinct transverse ridge in front of occipital pit, slightly curved posteromedially in dorsal view; pit surrounded laterally by tympanic spine base and anterior portion of parietal spine base; longitudinal length of pit greater than width of pit. Parietal and nuchal spines well developed, both spines broadly joined at base. Sphenotic with blunt spine. Postorbital bone vertically elongate, with several weak spinous points; located behind sphenotic spine; upper end of postorbital bone reaching anterior end of pterotic spine base. Pterotic spine simple, rounded, located just above uppermost end of preopercular ridge. Posttemporal spine simple, length of its base subequal to that of pterotic spine base; no upper posttemporal spine. Supracleithral spine simple.

Lateral surface of lacrimal with 6 low ridges radiating from center; uppermost end of upwardly directed ridge with bony protuberance directly below posterior nostril; uppermost end of dorsoanteriorly directed ridge with 2 (or 1) blunt spines; 3 ventrally directed ridges with distinct median ridge, tips not strongly projecting over upper lip, not forming a spinous point; backward ridge with distinct median ridge and lateral lacrimal spine. Suborbital ridge moderately developed, with 3 well-developed spines; first spine located at vertical through center of eye; second and third spines adjoining, located below posterior part of orbit. Broad space between ventral margin of orbit and suborbital ridge. Suborbital pit broad and deep, front rimmed by vertical lacrimal ridge. Preopercle with 5 blunt triangular spines; first and second spines with distinct median ridge; third to fifth spines without median ridge. Sharp supplemental preopercular spine present. Upper and lower opercular spines simple with well-developed median ridge.

Origin of first dorsal-fin spine above posttemporal spine base. Posterior margin of opercular membrane extending beyond vertical through base of third dorsal-fin spine. Posterior tip of longest pectoral-fin ray extending well beyond vertical through base of first anal-fin soft ray. Origin of pelvic fin anterior to base of uppermost pectoral-fin ray; posterior tip of depressed pelvic fin not reaching to anus. Origin of first anal-fin spine below origin of last dorsal-fin spine.

Color of preserved specimens: body brownish white; no distinct markings on head. Black blotch distally on membranes between first and fifth (or fourth) soft rays of dorsal fin. Lower halves of pectoral and anal fins blackish. Pelvic fin black, except for whitish base. Lower one-third of caudal fin black. Color when fresh unknown.

Distribution. Known from the western Pacific Ocean, from the Philippines, Vanuatu, and the Wallis and Futuna Islands in depths of 73–400 m ( Fig. 6 ). Likely to inhabit sandy bottoms.

Etymology. Derived from the Latin acutus meaning “sharp”, in reference to having the longest and sharpest snout of species in the genus.

Remarks. Pteroidichthys acutus can easily be distinguished from all other congeners by having a relatively long snout, its length longer than the postorbital length (vs. snout length shorter than postorbital length); the posterior margin of maxilla just reaching to or short of (vs. extending beyond) a vertical through the anterior margin of pupil; and the distance between the tips of the lateral lacrimal and first suborbital spines longer than (vs. shorter than or subequal to) that between the tips of the first and second suborbital spines. In addition, P. acutus differs from P. amboinensis and P. c a us s ei in having three spines and five soft rays in the anal fin (2 spines and 6 rays in the latter two species) and the supplemental preopercular spines present (vs. spine absent). Detailed comparisons of P. acutus with P. amboinensis are given under Remarks of the latter species.

Figures

FIGURE 1. Species of Pteroidichthys with three spines and five soft rays in the anal fin. A: P. noronhai, USNM 98892, holotype, 32.2 mm SL; B: P. noronhai, MNHN 2003 - 2409, 48.9 mm SL; C: P. acutus n. sp., MNHN 2001 - 2851, holotype, 38.7 mm SL; D: P. acutus n. sp., ASIZP 68097, paratype, 36.6 mm SL.

FIGURE 6. Distributional records of species of Pteroidichthys on the basis of specimens examined during this study. Circles, P. noronhai; stars, P. acutus n. sp.; triangles, P. amboinensis; diamonds, P. caussei n. sp. Literature records from the Indian Ocean (P. noronhai in the Saya de Malha Bank; P. amboinensis in the Red Sea and India) were omitted.

Tables

TABLE 2. Meristics and morphometrics, expressed as percentages of standard length, of holotype and paratypes of Pteroidichthys acutus n. sp.

Standard length (mm)	38.7	34.9–40.8
Meristics Dorsal-fin rays Pectoral-fin rays (left / right sides)	XII, 9 15 / 15	Modes XII, 9 XII, 9 14–16 / 14–15 15 / 15
Anal-fin rays Scale rows in longitudinal series Pored lateral-line scales	III, 5 35 -	III, 5 III, 5 34–36 35 20 20
Scale rows above lateral line Scale rows below lateral line Scale rows between last dorsal-fin spine base and lateral line Pre-dorsal scale rows	4 - 3 3	3–4 3 10–11 10 3–4 3 3 3
Gill rakers Morphometrics (% SL) Body depth	4 + 9 = 13 33.6	4–5 + 8–9 = 12–14 5 + 8 = 13 Means 29.4–35.2 32.7
Body width Head length Snout length	17.6 46.8 20.9	15.0–22.5 20.0 45.3–49.9 47.3 18.0–21.2 19.6
Orbit diameter Interorbital width at middle of eye Upper-jaw length	8.0 7.0 24.8	8.0–11.8 9.4 5.9–8.8 6.9 21.5–25.8 23.5
Postorbital length Pre-dorsal-fin length Pre-anal-fin length	21.2 43.4 73.9	17.2–20.9 18.1 38.7–43.4 41.5 68.1–73.9 71.3
Pre-pelvic-fin length 1st dorsal-fin spine length 2nd dorsal-fin spine length	43.2 12.9 16.0	33.5–44.0 41.2 10.3–12.9 11.3 11.7–16.0 13.6
3rd dorsal-fin spine length 4th dorsal-fin spine length 5th dorsal-fin spine length	18.1 19.6 22.0	13.7–18.1 15.3 13.7–19.6 16.7 15.0–22.0 17.2
6th dorsal-fin spine length	19.4	13.7–15.8 15.0 ......continued on the next page