Lestidiops sphyraenopsis Hubbs, 1916

Ho, Hsuan-Ching & Yang, Tsung-Yu, 2024, Redescriptions of two Lestidiops species (Aulopiformes: Paralepididae) from Japan, with comments on their morphology, Zootaxa 5481 (1), pp. 30-42 : 31-34

Lestidiops sphyraenopsis Hubbs, 1916

Figs. 1 , 2A ; Tables 1‒2

Lestidiops sphyraenopsis Hubbs, 1916:155 , pl. 18 (type locality: near shore, Avalon Bay, Santa Catalina Island, California, U.S.A.). Rofen 1966: 322 (mention). Post 1972:145 (type catalog). Fujii in Masuda et al. 1984:76 (short description). Nakabo 1993:317 (key). Ambrose in Moser et al. 1996:353 (early stages). Okiyama 1998: 241 (early stages). Fukui & Ozawa 2004:293 (list). Mundy 2005:204 (list). Okamoto et al. 2007:61 (early stages).

Lestidium sphyraenopsis : Harry 1953a: 195 (description).

Lestidium (Lestidiops) sphyraenopsis : Harry 1953b:240 (list).

Specimens examined. HUMZ 78448 (1, 355 mm SL), 37°51'N, 142°45'E, off Miyagi , Japan, 1350‒1440 m, 7 Oct. 1978 . K. Sakamoto. HUMZ 122294 (1, 323), no data . HUMZ 134997 (1), off Minamisanriku, Miyagi, Japan, 331 m, 17 Oct. 1994 . HUMZ 141369 (1), Pacific coast off Tohoku , Japan, bottom trawl, 6 Sep. 1995 . HUMZ 162123 (1, 338), off Shibotsu , Hokkaido, Japan . HUMZ 166595 (1), no data . HUMZ 178682 (1, 303) , HUMZ 178683 (1, 295), 39°40'12"N, 142°16'48"E, Miyako , Iwate, Japan, 412‒458 m, bottom trawl, 7 Oct. 2001 . HUMZ 179876 (1, 255) , HUMZ 179877 (1) , HUMZ 179878 (1) , HUMZ 179879 (1) , HUMZ 179880 (1), 39°42'36"N, 142°18'E, off Miyako , Iwate, Japan, 1 Jun. 2002 . HUMZ 192770 (1, 307), 39°45'N, 142°16'12"E, off Miyako , Iwate, Japan, 292‒312 m, 16 Oct. 2004 . HUMZ 209222 (1, 193), 35°40'48"N, 142°31'12"E, of Choshi , south of Tajima, Chiba, Japan, 890‒897 m, 8 Oct. 2010 . HUMZ 209223 (1, 194), 35°40'58.8"N, 142°31'01.2"E, off Miyako , Iwate, Japan, 890‒897 m, 8 Oct. 2010 . HUMZ 209339 (1, 305), 41°00'16.2"N, 141°47'04.2"E, off Rokkasho , Aomori, Japan, 517‒519 m, 15 Oct. 2010 . HUMZ 212858 (1, 173), 42°02'30"N, 141°37'12"E, Volcano Bay , Japan, 757‒811 m, otter trawl, 28 Nov. 2011 . HUMZ 214365 (1, 242), 38°55'28.8"N, 142°01'04.8"E, off Ofunato , Iwate, Japan, 17 Apr. 2012 . HUMZ 222680 (1, 315) , HUMZ 222681 (1, 380), 39°40’43.8”N, 142°17’46.8”E, off Miyako , Iwate, Japan, trawl, 481 m, 2 Oct. 2013 . HUMZ 224501 (1, ca. 281), 42°03’30”N, 141°36’48”E, off Tomakomai , Hokkaido, Japan, 740‒755 m, 8 Oct. 2014 . HUMZ 224579 (1, 332), 42°05’36”N, 141°35’36”E, off Funkawan , Hokkaido, Japan, otter trawl, 706 m, 20 Oct. 2014 . HUMZ 231511 (1, ca. 280), 41°55'24"N, 141°54'48"E, off Tomakomai , Hokkaido, Japan, trawl, 905‒ 948 m, 17 Sep. 2020 . HUMZ 231572 (1, 328), 41°57’54”N, 141°39’18”E, off Tomakomai , Hokkaido, Japan, bottom trawl, 17 Sep. 2020 . NSMT-P 35462 (1, 266), 36°29’06”N 149°59’48”E, east of Japan, 100 m, midwater trawl, 5 May 1987 . NSMT-P 49047 (1, 338), 40°20’48”N, 142°22’37.8”E, off northern Tohoku , Iwate, Japan, 805‒819 m, 6 Nov. 1995 . NSMT-P 53369 (24, 289‒352), 38°27'36"N, 142°01'33.6"E, off Miyagi, Iwate, Japan, 408‒415 m, trawl, 12 Apr. 1996 . NSMT-P 53610 (2, 326‒330), 37°51’01.8”N, 141°28’33.6”E, off Fukushima, Japan, 410‒415 m, trawl, 15 Apr. 1996 . NSMT-P 58802 (1, 253), 39°02’00”N, 143°30’06”E, off Miyasaki , Iwate, Japan, 650‒677 m, 30 Jul.1996 . NSMT-P 58803 (1, 273), 39°01’36”N, 143°30’24”E, Miyagi, Iwate, Japan, 550‒578 m, mesopelagic trawl, 30 Jul. 1996 . NSMT-P 58804 (2, 80‒256), 40°00’18”N, 144°56’54”E, Iwate, Japan, 25‒55 m, mesopelagic trawl, 15 Jul. 1996 . NSMT-P 58804 (3, 283‒340), 40°01’N, 143°50’18”E, Iwate, Japan, 530‒550 m, mesopelagic trawl, 13 Jul. 1996 . NSMT-P 58806 (3, 295‒300), 38°58’24”N, 143°29’18”E, Miyagi, Iwate, Japan, 600‒627 m, mesopelagic trawl, 30 Jul. 1996 . NSMT-P 58807 (2, 301‒370), 38°57’54”N, 143°27’54”E, Miyagi, Iwate, Japan, 450‒478 m, mesopelagic trawl, 29 Jul. 1996 . NSMT-P 58808 (2, 268‒333), 39°00’12”N, 143°29’42”E, Miyagi, Iwate, Japan, 650‒679 m, mesopelagic trawl, 30 Jul. 1996 . NSMT-P 92331 (1, 193), off Tohoku , Honshu, northern Japan, 23 Oct. 2008 .

Diagnosis. A relatively slender species of Lestidiops with body depth 16‒20 times in SL; anus well behind tip of appressed pelvic fin; lateral line incomplete but long, extending to above or slightly before posterior end of anal-fin base; head long, snout slender and pointed, its length 3‒4 times eye diameter; upper and lower margin of lateral line covered with melanophores; DFO well behind VFO and anus, V‒D 36.4‒42.9% V‒A; and V‒A very long, 25.5‒28.1% SL.

Description. Morphometric and meristic data are provided in Tables 1‒2 . Dorsal-fin rays 12‒13 (usually 12); pectoral-fin rays 12‒13 (usually 12); pelvic-fin rays 9; anal-fin rays 29–31 (rarely 28). Lateral-line scales: PVLL 37‒39, PDLL 48‒50, PALL 66‒68, TLL 103–112, including 27‒40 small ones on posterior portion. Vertebral counts: PHV 50–51, CV 47–50, PVV 38–41, PDV 48–51, PAV 65–68, and TV 98–102. Gill rakers on first gill arch 41‒56 in total, 9‒16 on upper limb (epibranchial) and 31‒44 on lower limb, including 18‒14 on ceratobranchial and 11‒23 on hypobranchial.

Body relatively slender, slightly thick, depth at pectoral fin 16‒21 in SL. Caudal peduncle moderately long, its length 1.6 (1.4‒1.9) times eye diameter ( Figs. 1A, B ). Ventral adipose fin not developed along abdominal ridge between pectoral and pelvic fins; well-developed on margin between anus and anal fin. Anus situated well behind tip of appressed pelvic fin, about one pelvic-fin length behind the fin tip and about midpoint of space between VFO and DFO ( Fig. 1C ).

Head relatively long and massive, its length 5.0‒ 5.5 in SL; snout long slightly blunt anteriorly, its length 1.7‒1.9 in HL ( Fig. 1D ). Mouth terminal, relatively large, its gape (mouth open) extending to slightly more than one eye diameter in front of eye. Lower jaw slightly upturned at tip, with small distal tab of fleshy tissue. Eye large, its diameter 5.7‒6.9 in HL. No light organ around eye. First suborbital bone slender, fifth and sixth bones not expanded posteriorly, and seventh small. Interorbital space narrow, its width 9.7‒11.3 in HL; some straight ridges present on top of head and snout. Two nostrils close to each other, located on posterior portion of snout, slightly more than one eye diameter before the eye; clearly in front of posterior end of premaxilla. Premaxilla long, extending to a point about half the eye diameter in front of eye. Numerous sensory canals on snout, check, operculum, and jaws; numerous sensory pores on dorsal surface of snout and lower surface of lower jaw.

Gill filaments present on all four gill arches. Fourth arch mostly connected to gill chamber wall by membranes. Pseudobranchs present, anterior half included in a deep pocket.

DFO situated at around posterior third of the fish, well behind VFO, predorsal length 1.5 in SL. Pectoral-fin base behind posterior margin of gill cover, upper end of fin base on imaginary horizontal line drawn through lower margin of eye; no small pocket behind fin base. VFO slightly behind midpoint of the fish, well before dorsal fin, pre-pelvic-fin length 1.8‒1.9 in SL. Anus well behind tip of appressed pelvic fin, by more than half of pelvic-fin length, and at about midpoint of space between VFO and DFO. A tiny axial scale behind pelvic-fin base. Anal fin originating in posterior fifth of body, pre-anal length 1.2 in SL. Dorsal adipose fin over rear portion of anal-fin base, its base length slightly smaller than eye diameter.

Two or three small fangs at tip of upper jaw, followed by single row of small, retrorse teeth, these gradually becoming smaller on posterior part of jaw. Vomerine teeth absent. One to three fangs (either depressible or fixed) at front end of each lower jaw, followed by two rows of small fangs arranged in about 7 or 8 pairs; those of inner row very long with knife-like tip and depressible; those in outer row much shorter (about 1/ 4 in length of the accompanied inner tooth), curved, and fixed. Two rows of fangs on each palatine with anteriormost teeth arranged in 5‒7 pair, those in inner row long and depressible, on outer row small and fixed, followed by single row of small, fixed teeth on posterior part of palatine. No or just a few small teeth on tongue; if present, restricted on posterior portion of tongue.

Shield-shaped gill rakers present on epibranchial, ceratobranchial, and hypobranchial parts of each gill arch, each raker with 2‒3 (rarely more) slender teeth on broad base, these teeth extending slightly upward beyond margin of gill arch. Teeth on pharyngeal arch long, arranged in an oval patch with about 6 rows in middle. Single row of small teeth on fifth ceratobranchial.

Body scaleless, except for single row of lateral-line scales extending from above pectoral girdle to point above approximately fourth-fifths length to posterior end of anal-fin base. Lateral-line scales slightly wider than high, gradually becoming narrower and smaller posteriorly, with many strongly reduced scales on posterior portion; one large pore on each upper and upper and lower anterior corner of all large scales and upper and lower ends of small scales.

Luminescent duct absent.

Size. The largest specimen examined is 380 mm SL, but reported up to 390 mm SL (Fujii in Masuda et al., 1984).

Coloration ( Figs. 1A, B ). Body light brown in general, with dorsum covered by dense tiny melanophores. Snout, lower jaw and space behind eye darker. Black patch on posterior portion of frontal bones and top of skull.

Smaller specimens (<300 mm SL) generally paler, with a band of large, loosely arranged melanophores along upper margin of lateral line, a non-pigmented gap between the tiny melanophores of dorsum and large melanophores below; fewer large melanophores on lateral-line scales and lower margin of lateral line, leaving large non-pigmented space on most abdominal areas below lateral line; loose melanophores on middle of abdominal ridge; melanophores becoming more scattered on posterior portion behind pelvic fin. On posterior portion behind pelvic fin, gradually covered evenly with melanophores. Margins of caudal peduncle darker, with upper margin broader than lower. All fins light brown, covered evenly with melanophores; adipose fin darker. Mouth cavity pale; inner side of gill cover and branchiostegal membranes black; gill chamber black; gill arches pale. Isthmus covered with sparsely distributed melanophores. Peritoneal membranes black.

Pigmentation gradually denser in specimens larger than 300 mm SL, heavily covered with melanophores, including lateral line and abdominal region in specimens more than 350 mm SL. A large specimen (ca. 380 mm SL) has dorsum dark brown with tiny melanophores; entire body, including head, lateral sides and abdominal region evenly and heavily covered with larger melanophores.

Distribution. Widespread in the northern Pacific Ocean off Japan (ca. 36‒ 42°N) and along the coastline of northern America (ca. 35‒ 44°N), with some exceptions, e.g., one from the middle of northeastern Pacific (HUMZ 220419) and one from off southern Mexico (SIO 63-882) ( Fig. 2A ). Mundy (2005) suggested that it could be expected in the northern Hawaiian Ridge based on its known range and tentatively identified larval specimens from 28°N, 155°W ( Loeb, 1979). Bathymetric range 292‒1440 m in Japan, generally collected at depths of 400‒1000 m, with two lots collected by midwater trawl at depths of 25‒55 m and 100 m, respectively. Based on collected specimens, L. sphyraenopsis is relatively abundant in the northwestern Pacific Ocean, compared to those in the northeastern Pacific Ocean (this study; also see http://www.fishnet2.net/).

Remarks. An 80 mm SL specimen has relatively short snout (8.5% SL), whereas larger specimens have a relatively slender snout (10.0‒11.4% SL). This would suggest that growth changes in snout length occur, similar to other paralepidids.

Figures

FIGURE 1. Lestidiops sphyraenopsis Hubbs, 1916. HUMZ 224579, 332 mm SL, off Funkawan, Hokkaido, Japan, fresh, photo by HUMZ. B‒E. NSMT-P53369, 1 of 24, 340 mm SL, off Miyagi, Honshu, northern Japan, anterior to right. B. Lateral view. C. Lateral view of mid-trunk showing origins of dorsal, pelvic and anal fins (bars). Arrow points to anus. D. Lateral view of head. E. ventral view of mid-trunk, arrow points to anus.

FIGURE 2. Distribution maps of two Lestidiops species. A. L. sphyraenopsis Hubbs, 1916. B. L. ringens (Jordan & Gilbert, 1880), the distribution range in northeastern Pacific is shaded with stipple. Solid symbol represents the holotype of each. One symbol may represent more than one capture.