Allinectes istiophorus, Orr, 2025

Allinectes istiophorus , new species urn:lsid:zoobank.org:act:9623EDD5-7495-40A6-93F1-896A0C103CB5

Sailfin Snailfish

Figures 1 View FIGURE 1 , 2B View FIGURE 2 , 4B View FIGURE4 , 5B View FIGURE 5 , 6B View FIGURE 6 ; Tables 2 View TABLE 2 and 3 View TABLE 3

Careproctus ectenes View in CoL , non Gilbert: Maslenikov et al. 2013: 14, fig. 2D (Alaska, new records).— Orr et al. 2014a: 166, table 2 (list of identifications).— Orr et al. 2014b: 20, table 1 (list of identifications).— Love et al. 2021: 136 View Cited Treatment (in part; checklist).

Holotype. UW 117193 , 94.3 mm, ripe female, Aleutian Islands , Seguam Pass, 52.3353°N, 172.7493°W, 459 m depth, 21 June 2006, F/V Gladiator , cruise 2006-01, haul 53, benthic bag, J. W. Orr. GoogleMaps

Paratypes. 87 specimens: 62.7–120.5 mm. Aleutian Islands : UW 202383 (out of 117193), 108 mm, same locality as holotype ; UW 200693, 107 mm, ripe male, 52.3310°N, 172.7470°W, 447 m depth, 23 July 2002, F/ V Sea Storm , cruise 2002-01, haul 156, J.W. Orr GoogleMaps ; UW 200696, 92 mm, 53.1899°N, 169.8622°W, 404 m depth, 19 July 2002, F/ V Vesteraalen , cruise 2002-01, haul 195, benthic bag, R. N. Clark GoogleMaps ; UW 155355, 108 mm, CT scan, 52.4061°N, 170.5475°W, 408 m depth, 16 June 2006, F/ V Sea Storm , cruise 2006-01, haul 39, B. Knoth GoogleMaps ; UW 201411, 8, 100–118 mm, 52.3255°N, 172.7466°W, 457 m depth, 19 June 2004, F/ V Sea Storm , cruise 2004-01, haul 60, J. W. Orr GoogleMaps ; UW 200695, 110 mm, 52.4255°N, 170.5257°W, 400 m depth, 3 August 2002, F/ V Sea Storm , cruise 2002-01, haul 195, R. C. Harrison GoogleMaps ; UW 204155 (ex UW 201425), 105 mm, 52.3732°N, 171.3548°W, 330 m depth, 10 August 2002, F/ V Sea Storm , cruise 2002-01, haul 225 GoogleMaps ; UW 200681, 6, 84–120 mm, 52.3334°N, 172.7459°W, 439 m depth, 22 June 2018, F/ V Ocean Explorer , cruise 2018-01, haul 52 GoogleMaps ; UW 200687, 2, 100–110 mm, 52.2436°N, 171.7035°W, 418 m depth, 17 June 2016, F/ V Sea Storm , cruise 2016-01, haul 44, C. L. Conrath GoogleMaps ; UW 117487, 2, 94.5–103.1 mm, 52.4261°N, 170.5243°W, 403 m depth, 30 May 2000, F/ V Vesteraalen , cruise 2000-01, haul 46, benthic bag, W. C. Flerx GoogleMaps ; UW 117494, 118.3 mm, 52.3282°N, 172.7468°W, 450 m depth, 4 June 2000, F/ V Vesteraalen , cruise 2000-01, haul 67, W. C. Flerx GoogleMaps ; UW 117495, 3, 102.0– 120.5 mm, 52.3282°N, 172.7468°W, 450 m depth, 4 June 2000, F/ V Vesteraalen , cruise 2000-01, haul 67, W. C. Flerx GoogleMaps ; UW 117497, 81.4 mm, 51.9066°N, 176.6378°E, 376 m depth, 1 August 1997, F/ V Dominator , cruise 1997-01, haul 201, benthic bag, R. C. Harrison GoogleMaps ; UW 117522, 97.5 mm, 52.6520°N, 172.2511°W, 386 m depth, 5 June 2000, F/ V Dominator , cruise 2000-01, haul 79, benthic bag, J. W. Orr GoogleMaps ; UW 153151, 119 mm, 52.6453°N, 172.2730°W, 398 m depth, 26 June 2010, F/ V Sea Storm , cruise 2010-01, haul 68, benthic bag, J. W. Orr GoogleMaps ; UW 154887, 2, 92.1–96.3 mm, 52.9352°N, 169.3369°W, 399 m depth, 15 June 2014, F/ V Sea Storm, cruise 2014-01, haul 19, benthic bag, V. Simon GoogleMaps ; UW 200680, 5, 96–117 mm, 52.3334°N, 172.7459°W, 439 m depth, 22 June 2018, F/ V Ocean Explorer , cruise 2018-01, haul 52 GoogleMaps ; UW 200690, 3, 78–97 mm, 53.0972°N, 171.7007°E, 464 m depth, 1 August 2004, F/ V Gladiator , cruise 2004-01, haul 227, R. N. Clark GoogleMaps ; UW 200693, 4, 81.8–110.0 mm, 52.331°N, 172.7470°W, 447 m depth, 23 July 2002, F/ V Sea Storm , cruise 2002-01, haul 156, J. W. Orr GoogleMaps ; UW 200988, 98 mm, 52.2440°N, 171.6998°W, 394 m depth, 6 August 2002, F/ V Sea Storm , cruise 2002-01, haul 211, R. C. Harrison GoogleMaps ; UW 201094, 110 mm, 56.1903°N, 169.4878°W, 482 m depth, 16 July 2002, F/ V Morning Star , cruise 2002-02, haul 120, D. E. Stevenson GoogleMaps ; UW 201178, 62.7 mm, 51.9438°N, 178.0691°E, 435 m depth, 6 July 2002, F/ V Sea Storm , cruise 2002-01, haul 99, benthic bag, J. W. Orr GoogleMaps ; UW 117499, 90 mm, 53.0953°N, 171.6970°E, 465 m, 4 August 1997, F/ V Vesteraalen , cruise 1997-01, haul 220, J. W. Orr GoogleMaps ; UW 116041, 2, 96.8–101.3 mm, 52.2172°N, 171.6353°W, 453 m depth, 16 June 2004, F/ V Sea Storm , cruise 2004-01, haul 44, J. W. Orr GoogleMaps ; UW 116042, 12, 68–113 mm, 52.3405°N, 172.7455°W, 448 m depth, F/ V Morning Star, cruise 2002-01, haul 32, J. W. Orr GoogleMaps ; UW 116234, 3, 99.6–112.0 mm, 52.4873°N, 172.5612°W, 411 m depth, 22 June 2006, F/ V Gladiator , cruise 2006-01, haul 56, J. W. Orr GoogleMaps ; UW 117236, 98.0 mm, 52.2456°N, 171.6994°W, 409 m depth, 17 June 2006, F/ V Gladiator , cruise 2006-01, haul 40, benthic bag, J. W. Orr GoogleMaps ; UW 150772, 105 mm, 52.3278°N, 172.7467°W, 450 m depth, 26 June 2010, F/ V Sea Storm , cruise 2010-01, haul 64, benthic bag, J. W. Orr GoogleMaps ; UW 150774, 120 mm, 52.3278°N, 172.7467°W, 450 m depth, 26 June 2010, F/ V Sea Storm , cruise 2010-01, haul 64, J. W. Orr GoogleMaps ; UW 200700, 75.6 mm, 52.4094°N, 170.6192°W, 319 m depth, 3 August 2002, F/ V Sea Storm , cruise 2002-01, haul 198, R. C. Harrison GoogleMaps ; Bering Sea: UW 200684, 100 mm, 56.1003°N, 168.5398°W, 451 m depth, 2 July 2010, F/ V Vesteraalen , cruise 2010-01, haul 126, S. Kotwicki GoogleMaps ; UW 157982, 107 mm, 56.1652°N, 169.3980°W, 629 m depth, 6 July 2012, F/ V Vesteraalen , cruise 2012-01, haul 110, S. Kotwicki GoogleMaps ; UW 159980, 98 mm, 56.1417°N, 169.4517°W, 630 m depth, 1 March 2009, R / V Oscar Dyson , cruise 1DY09/12/2/NOR, haul 1 GoogleMaps ; UW 118635, 110 mm, 57.8157°N, 173.8599°W, 524 m, 26 June 2008, J. W. Orr, F/ V Vesteraalen , cruise 2008-01, haul 67 GoogleMaps ; UW 116032, 104 mm, 56.1913°N, 169.4864°W, 485 m depth, 20 July 2004, F/ V Northwest Explorer , cruise 2004-01, haul 158, J. W. Orr GoogleMaps ; UW 200689, 91.1 mm, 56.1904°N, 169.4873°W, 487 m depth, 20 July 2016, F/ V Cape Flattery , cruise 2016-01, haul 122, N. E. Roberson GoogleMaps ; UW 200682, 89.1 mm, 56.1233°N, 168.7844°W, 563 m depth, 1 July 2010, F/ V Vesteraalen , cruise 2010-01, haul 121, S. Kotwicki GoogleMaps ; UW 200688, 99.7 mm, 56.1384°N, 169.4461°W, 638 m depth, 19 July 2016, F/ V Cape Flattery , cruise 2016-01, haul 120, N. E. Roberson GoogleMaps ; UW 201522, 90 mm, 56.0686°N, 168.7603°W, 762 m depth, 17 July 2016, F/ V Cape Flattery , cruise 2016-01, haul 112, N. E. Roberson GoogleMaps ; UW 119724, 90 mm, 56.2033°N, 169.247°W, 498 m depth, 5 October 2007, R / V Miller Freeman , cruise 2007-12, haul 3, D. E. Stevenson GoogleMaps ; SIO 94 -198, 3, 104.0– 116.5 mm, 52.3217°N, 172.7450°W, 458 m depth, 16 June 1994, F/ V Pacific Knight , cruise 1994-01, haul 54, W.C. Flerx GoogleMaps ; SIO 94 -199, 112.8 mm, 52.4945°N, 172.5597°W, 470 m depth, 16 June 1994, F/ V Pacific Knight , cruise 1994-01, haul 55, W. C. Flerx GoogleMaps ; UAM:Fish 4094 (ex UW 204156), 2, 96.4–101.6 mm, 52.9218°N, 169.3647°W, 406 m depth, 16 June 2018, F/ V Sea Storm , cruise 2018-01, haul 22, P. Von Szalay GoogleMaps ; UAM:Fish 4095 (ex UW 200986), 80 mm, 52.3778°N, 170.5854°W, 368 m depth, 3 August 2002 -01, F/ V Sea Storm , cruise 2002-01, haul 197, R. C. Harrison GoogleMaps .

Diagnosis. Distinguished from all other species of Allinectes by the combination of its extremely elongate anterior dorsal-fin rays, dark stomach, and black peritoneum. Most similar to A. busbyi , new species, from which it differs in its rounded snout (vs. strongly protruding snout in A. busbyi , new species), longer anterior dorsal-fin rays (65.0–102.7% vs. 60.5% HL), larger orbit (length 27.5–34.2% vs. 26.1% HL), shorter postorbital length (32.2–42.4% vs. 44.1% HL), and more slender caudal-fin base (8.0–14.3% vs. 14.7% HL). Differing from A. nanstanorum , new species, in its longer anterior dorsal-fin ray (65–102.7% vs. 28.7–33.0% HL in A. nanstanorum , new species), caudal fin truncate or slightly emarginate (vs. dorsalmost caudal-fin ray longer and thicker), higher count of pectoral-fin rays (32–37 vs. 30–31), body overall light-red (vs. dark red and black), stomach dark (vs. pale), and abdomen white (vs. dark). Differing from A. ectenes in peritoneum black (vs. pale in A. ectenes ), fewer vertebrae and median-fin rays (48–51 vs. 54 vertebrae, 43–47 vs. 48–51 dorsal-fin rays, and 38–41 vs. 44 anal-fin rays), narrower head (44.2–58.6% vs. 61.5% HL), and typically larger pelvic disk (29.7–41.4% vs. 30.8% HL). Differing from A. curilanus in having snout tip slightly protruding beyond lower jaw (vs. strongly protruding snout tip), caudal fin longer (49.2–66.3 vs. 33.8–50.9% HL), and fewer vertebrae (48–51 vs. 53–59 in A. curilanus ) and median-fin rays (dorsal 43–47 vs. 48–54; anal 38–41 vs. 42–49). Similar to A. attenuatus , known only from holotype, differing in having fewer dorsal-fin rays (43–47 vs. 48 in A. attenuatus ), deeper body at anal-fin origin (50.2–82.1% vs. 38.8% HL), longer pre-anal-fin length (33.9–41.6% vs. 32.4% SL), and anus closer to disk (3.2– 17.4% vs. 24.7% HL) and farther from anal-fin origin (49.3–75.6% vs. 29.4% HL). Further distinguished from A. pycnosoma by its strongly notched pectoral fin with long lower lobe (vs. shallow notch, with short lower lobe in A. pycnosoma ), shorter head (19.8–24.8% vs. 26.9% SL), and anus far from pelvic disk (3.2–17.3% vs. 25.7% HL).

Description. Body elongate, slightly tapered, rounded anteriorly, compressed posteriorly; depth at pelvic disk 44.2–76.8 (55.9)% HL; depth at anal-fin origin 50.2–82.1 (60.7)% HL. Head moderately small, 19.8–24.8 (22.4)% SL, width 44.3–58.6 (51.2)% HL; broadly depressed, nape slightly elevated. Snout typically longer than orbit, 88.3–129.6 (118.0)% OL, 27.2–36.7 (34.1)% HL, slightly rounded, snout tip slightly projecting anterior to lower jaw, 0–7.7 (7.1)% HL. Mouth inferior; upper jaw 33.4–43.9 (37.0)% HL, maxilla extending to mid-orbit, oral cleft extending to anterior rim of orbit; mandible 41.1–51.8 (44.1)% HL. Premaxillary tooth plates matching mandibular tooth plates. Premaxillary and mandibular teeth trilobed in 7–9 oblique rows of 7–8 teeth forming moderately wide bands. Diastema absent at symphyses of upper and lower jaws. Orbit length 27.5–34.2 (28.9)% HL, orbit depth 19.3–30.6% HL, dorsal margin below dorsal contour of head, suborbital depth to upper jaw 7.9–16.6 (14.2)% HL, to lower jaw 19.5–25.9 (21.8)% HL; pupil round. Interorbital space convex, broad, fleshy distance 23.2–39.4 (30.3)% HL, bony distance 16.3–25.0 (19.9)% HL. Nostril single, with well-developed tube at level with upper part of orbit; nostril tube length 6.4–22.5 (13.1)% OL.

Free neuromasts often evident in preserved specimens: at least four or five extending posteriorly from suprabranchial pore 2. In one specimen ( UW 116234 ), about 28 pores extend to form arch over pectoral fin, curving ventrally to midbody at anal-fin origin, and continuing to near caudal-fin base.

Symplectic with broad dorsal flange extending onto quadrate and metapterygoid ( Fig. 5B View FIGURE 5 ).

Gill opening small, 20.2–30.6 (22.8)% HL, upper margin at level of dorsal rim of orbit, extending ventrally to above pectoral-fin or to base of pectoral-fin rays 1–4 (ray 1). Gill rakers 6–9 (8; Table 2 View TABLE 2 ).

Dorsal-fin rays 43–47 (44; Tables 2 View TABLE 2 , 3 View TABLE 3 ), anteriormost rays elongate, ray 1 58.8–102.75 (73.0)% HL, typically longer than all succeeding rays, rarely ray 2 slightly longer or about equal in length, followed by shorter rays 3 and 4 or 5, forming deep notch, followed by longer rays 5 or 6, succeeding rays of equal length, anteriormost rays 1 to 4 or 5 deeply emarginate. Anteriormost dorsal-fin pterygiophore inserted between neural spines 2 and 3 or 3 and 4 (3 and 4). Pre-dorsal-fin length 23.2–27.1 (23.9)% SL.

Anal-fin rays 38–41 (39; Tables 2 View TABLE 2 , 3 View TABLE 3 ), two to three (two) anal-fin pterygiophores anterior to first haemal spine, tips of all rays not exserted. Anal-fin origin below vertebrae 11–12 (caudal vertebrae 1–2), pre-anal-fin length 33.9–41.6 (36.7)% SL.

Pectoral fin deeply notched, with 32–37 (32) rays ( Tables 2 View TABLE 2 , 3 View TABLE 3 ). Upper lobe 65.5–83.9 (74.9)% HL, with 22–30 (24) rays, extending well beyond anus to anal-fin origin or slightly beyond, about same length or slightly longer than lower lobe, dorsalmost rays lengthening to rays 6–8, more ventral rays gradually shortening to shortest ray of notch. Lower lobe elongate, 59.3–104.6 (69.2)% HL, with 6–10 (8) rays, extending well beyond anus to or near anal-fin origin; dorsal rays lengthening to elongate rays, more ventral rays gradually shortening to ventralmost ray near pectoral symphysis. Tips of rays 5–20% free of membrane, elongate rays of lower lobe up to 65% free of membrane. Notch strong, rays in notch slightly more widely spaced than rays of lobes, more widely spaced ventrally. Uppermost pectoral-fin ray level with midorbit. Insertion of lowermost pectoral-fin ray below mid-orbit.

Proximal pectoral radials four (3+1), robust; radials 1 and 2 hourglass shaped, radial 3 notched dorsally, radial 4 ovoid, unnotched, not widely spaced from radial 3 ( Fig. 6B View FIGURE 6 ). Three large fenestrae present: scapular fenestra and fenestra between radials one and two ovoid, fenestra between two and three dorsoventrally elongate. Anterodorsal margin of basal cartilage pointed, distinct hook absent. Scapula with strong helve; coracoid narrowly triangular with broad lamina. Distal radials always present at base of pectoral-fin rays 2 to 29, more ventral distal radials reduced. Distal radials of ventralmost four rays absent, rays articulating directly with non-staining fibrocartilage.

Pelvic disk moderately large, length 29.7–41.4 (38.9)% HL, slightly longer than wide, width 23.0–41.0 (33.7)% HL, anterior lobe weakly developed, flat, distance from snout to pelvic disk 11.7–15.7 (12.3)% SL. Anus below dorsal-fin origin, much nearer to pelvic disk than anal-fin origin, distance from disk to anus 3.2–17.4 (13.3)% HL, distance from anus to anal-fin origin 49.4–75.6 (65.9)% HL; distance from snout to anus 20.3–26.4 (22.4)% SL, 96.7–111.0 (100.0)% HL.

Caudal fin truncate to slightly emarginate. Principal caudal-fin rays 11–12 ( Table 2 View TABLE 2 ), dorsal procurrent rays 1–3, ventral procurrent rays 0–2 (1–3 + 5–6/6 + 0–2) (2 + 5/6 + 1). Caudal fin 49.2–66.3 (59.2)% HL. Dorsal-fin rays attached to caudal fin 22.2–40.9 (28.0)% CL; anal-fin rays, 25.9–53.8 (46.4)% CL. Depth at base of caudal fin 14.6–25.2 (20.1)% CL.

Vertebrae 48–51 (49), precaudal 9–11 (10), caudal 38–41 (39; Tables 2 View TABLE 2 , 3 View TABLE 3 ). Pleural ribs 2 or 3 (3), anteriormost small to minute when 3, others long and slender, present on vertebrae 9–10 or 8–10 (8–10). Hypural plate composed of dorsal and ventral plates divided by small distal notch.

Skin thin, close to body. Pyloric caeca 7–11, long, length about 30–38% HL, center-left side of visceral cavity.

Coloration. Body and fins pink to red in life ( Fig. 4B View FIGURE4 ); head slightly darker, dark orobranchial cavity showing through operculum; belly with bright white extending from pectoral-fin base to anal-fin origin, ventrally from just lateral to midline, dorsally to level of dorsal margin of gill slit; peritoneum black, evident externally in a narrow region dorsally between the white belly and reddish pink of body. Iris silver. Body and fins pale in preservation. Peritoneum black; orobranchial cavity dusky dark; stomach dusky, darkly streaked, or black, intestines pale, pyloric caeca pale, and urogenital papilla pale.

Distribution. Allinectes istiophorus has been collected across the length of the Aleutian Islands from west of Attu Island on Stalemate Bank to Samalga Pass and north in the Bering Sea to Zhemchug Canyon at 57.8157°N, 173.8598°W ( Fig. 1 View FIGURE 1 ). Collection depths range from 117 to 762 m.

Life history. The largest specimen examined was 120.5 mm (UW 117495), a ripe male with enlarged testes; the smallest ripe male was 81.8 mm (UW 200693). The smallest ripe female with yolked eggs was 81.4 mm (UW 117497). Ripe yolked eggs were about 4.0–5.0 mm in diameter. One individual was recovered from the stomach contents of a Pacific Halibut ( Hippoglossus stenolepis Schmidt ).

Etymology. The specific epithet istiophorus is taken from the Greek ἱστioν, meaning “sail,” and φέρω, meaning “I bear,” alluding to the elongate anterior dorsal-fin rays.

Remarks. In AFSC resource assessment surveys in Alaska, A. istiophorus has been routinely misidentified as A. ectenes ( Maslenikov et al. 2013; Orr et al. 2014a, b) because of its slender body, moderate-sized pelvic disk, small gill slit, and long anterior dorsal-fin rays.