Allinectes attenuatus (Gilbert & Burke, 1912), 2025

Allinectes attenuatus (Gilbert & Burke, 1912) , new combination

Attenuate Snailfish

Figure 1 View FIGURE 1 ; Tables 1 View TABLE 1 and 2 View TABLE 2

Careproctus attenuatus Gilbert & Burke, 1912a: 79 View in CoL , fig. 24 (original description, compared with A. ectenes). Type locality: Alaska, Aleutian Islands, off Agattu Island, 882 m (482 fms), Albatross station 4781.— Gilbert & Burke 1912b: 374 (compared with C. homopterus Gilbert & Burke, 1912b).— Burke 1930: 116, fig. 34–35 (description, key, compared with C. homopterus).— Soldatov & Lindberg 1930: 379 (description, possibly in Russian waters, compared with C. hamopterus [sic]).— Stein & Fitch 1984: 82, fig. 2 (otolith, specimen not found).— Lindberg & Krasyukova 1987: 438, fig. 259 (description, in key, compared with C. homopterus).— Kido 1988: 198 (compared with A. jordani).— Pitruk 1990: 36 (checklist, Sea of Okhotsk).— Parin et al. 2002: S110 ( Russia, possibly in Sea of Okhotsk and off Commander Islands).— Chernova et al. 2004: 5 (checklist, unconfirmed report to Sea of Okhotsk).— Orr & Busby 2006: 13 (compared with Allocareproctus).— Orr & Maslenikov 2007: 708 View Cited Treatment (compared with C. comus Orr & Maslenikov, 2007 and C. faunus Orr & Maslenikov, 2007).— Kai et al. 2011: 353 (compared with C. notosaikaiensis Kai, Ikeguchi & Nakabo, 2011).— Parin et al. 2014: 315 (checklist, possible record from Commander Islands).— Murasaki et al. 2018: 240 (list of characters, compared with C. surugaensis).— Kai et al. 2018: 421 (compared with C. iacchus Kai, Tohkairin, Fuiwara & Hamatsu, 2018).—Kai & Matsuzaki 2020: 137 (compared with C. longidigitus Kai & Matsuzaki, 2020).— Chernova et al. 2020: 84 (compared with C. pulcher Chernova, Thiel & Eidus, 2020)— Dylidin & Orlov 2020: 209 (checklist, unconfirmed from Sakhalin Island).

Careproctus attinuatus : Ueno 1971: 98 (lapsus calami, Sea of Okhotsk).

Careproctus attenuatus View in CoL non Gilbert & Burke: Steinke et al. 2009: fig. 4, supplements (molecular phylogenetics, = C. longifilis Garman, 1892).— Duhamel et al. 2010: 322 (molecular phylogenetics, = C. longifilis).— Orr et al. 2019: 54 (molecular phylogenetics; corrected misidentifications to C. longifilis).

Careproctus attenuates : Burke 1930: 116 (lapsus calami, description of type).— Chernova et al. 2020: 84 (lapsus calami; compared with C. pulcher).

Careproctus attenuates non Burke: Linley et al. 2022: 11 (phylogenetics, = C. longifilis).

Holotype. USNM 74386 About USNM , 37 mm SL ( Gilbert & Burke 1912a; now broken anterior to caudal fin), Alaska, Aleutian Islands, off Agattu Island , Albatross station 4781 , 52.24°N, 174.22°E, 482 fms (881 m), 7 June 1906. GoogleMaps

Diagnosis. Distinguished from all other species of Allinectes by a combination of its truncate non-protruding snout and slender posterior body (depth at anal-fin origin 38.8% vs. 39.7–82.1% HL in other Allinectes ). Further distinguished from A. ectenes , A. istiophorus , new species, A. nanstanorum , new species, and A. busbyi , new species, by its slightly notched dorsal fin (vs. more elongate anteriormost rays and deep notch in A. ectenes , A. istiophorus , new species, A. nanstanorum , new species, and A. busbyi , new species), from A. istiophorus , new species, and A. busbyi , new species, by stomach pale (vs. dark in A. istiophorus , new species, and A. busbyi , new species), from A. istiophorus , new species, A. nanstanorum , new species, and A. busbyi , new species, by its higher count of dorsal-fin rays (48 vs. 43–47 in A. istiophorus , new species, 45 in A. busbyi , new species, and 42–45 in A. nanstanorum , new species) and smaller pelvic disk (28.2% HL vs. 29.7–41.4%, 40.2%, and 29.0–29.8% HL in A. istiophorus , new species, A. busbyi , new species, and A. nanstanorum , new species, respectively), and from A. ectenes by its higher count of pectoral-fin rays (34 vs. 30–32 in A. ectenes ), peritoneum black (vs. pale), and snout truncate (vs. snout rounded to strongly protruding). Easily distinguished from A. curilanus by its truncate, non-protruding snout (vs. acute, strongly protruding snout in A. curilanus ), lower counts of anal-fin rays (40 vs. 42–49), deeper body at pelvic disk (67.1% vs. 38.7–72.5% HL), more slender body posteriorly (depth at anal-fin origin 38.8% vs. 39.7–53.0% HL), and a shorter distance from anus to anal-fin origin (29.4% vs. 31.1–74.4% HL). Further distinguished from A. pycnosoma by its deeply notched pectoral fin with long lower lobe (vs. shallow notch, with short lower lobe in A. pycnosoma ), higher counts of dorsal-fin rays (48 vs. 45), and larger mouth (upper-jaw and lower-jaw lengths 41.2% and 47.1%, respectively, vs. 28.6% and 38.1% HL).

Description. Body extremely elongate, greatly attenuated ( Gilbert & Burke 1912a; Burke 1930), rounded anteriorly, compressed posteriorly; depth at pelvic disk 67.1% HL, depth at anal-fin origin 38.8% HL. Head relatively large, 23.0% SL, width 58.8% HL, depressed, broad, with truncate snout, nape strongly elevated. Snout deep, truncate, not projecting anterior to lower jaw, length 27.1% HL. Snout shorter than orbit length, 85.2% OL, 27.1% HL. Mouth terminal; upper jaw 41.2% HL, maxilla extending to midorbit, oral cleft extending to anterior part of orbit; mandible 47.1% HL. Premaxillary and mandibular teeth trilobed in 7 oblique rows ( Gilbert & Burke 1912a), forming narrow bands. Orbit 31.8% HL, dorsal margin below dorsal contour of head, suborbital depth to upper jaw 8.2% HL, to lower jaw 24.7% HL; pupil round. Interorbital space broad, bony distance 21.2% HL, slightly convex. Nostril on short tube, level with midorbit, length 14.8% OL.

Gill opening small, upper margin at level of dorsal rim of orbit, entirely above pectoral fin ( Gilbert & Burke 1912a).

Dorsal-fin rays 48 ( Burke 1930; Tables 1 View TABLE 1 , 2 View TABLE 2 ), anteriormost ray moderately elongate, longer than succeeding rays 2 and 3, forming slight notch ( Burke 1930). Anteriormost dorsal-fin pterygiophore inserted between neural spines 3 and 4. Pre-dorsal-fin length 25.4% SL.

Anal-fin rays 40 ( Burke 1930; Tables 1 View TABLE 1 , 2 View TABLE 2 ), two anal-fin pterygiophores anterior to first haemal spine, each bearing a single ray, tips of rays not exserted ( Gilbert & Burke 1912a: fig. 24). Anal-fin origin below vertebra 12 (caudal vertebra 2), pre-anal-fin length 32.4% SL.

Pectoral fin moderately notched, with 34 rays ( Tables 1 View TABLE 1 , 2 View TABLE 2 ), damaged ( Gilbert & Burke 1912a; Burke 1930). Upper lobe moderately elongate ( Gilbert & Burke 1912a: fig. 24). Lower lobe moderately elongate, 1.5 in head ( Burke 1930; about 75% HL), with nine rays ( Gilbert & Burke 1912a: fig. 24), extending to anus, well short of anal-fin origin ( Gilbert & Burke 1912a: fig. 24). Longer rays of lower lobe mostly free of membrane ( Gilbert & Burke 1912a: fig. 24). Notch strong. Uppermost pectoral-fin ray level with ventral part of orbit; insertion of lowermost pectoral-fin ray below posterior rim of orbit ( Gilbert 1912a: fig. 24).

Pelvic disk small, length 28.2% HL, slightly longer than wide, width 24.7% HL, flat, distance from tip of snout to pelvic disk 15.7% SL. Anus about midway between pelvic disk and anal-fin origin, distance from disk 24.7% HL, distance from anal-fin origin 29.4% HL; distance from snout to anus 26.3% SL, 114.0% HL.

Caudal fin broken ( Gilbert & Burke 1912a), now missing with posterior part of body. Membrane of posterior dorsal- and anal-fin rays attached for about 33% CL ( Gilbert & Burke 1912a).

Vertebrae>48, precaudal 10, caudal>38 ( Tables 1 View TABLE 1 , 2 View TABLE 2 ). Pleural ribs 3, anteriormost small, others long and slender, present on vertebrae 8–10.

Skin thin, prickles absent. Pyloric caeca about 10 ( Burke 1930).

Coloration. In life, body “tinged with light red” ( Gilbert & Burke 1912a). In preservation, uniformly pale. Peritoneum dark; stomach, pyloric caeca, and intestines pale; roof of mouth dusky, gill cavity otherwise pale.

Life history. The holotype was 37 mm SL at the time of its original description ( Gilbert & Burke 1912a).

Distribution. Allinectes attenuatus is known only from the holotype, collected in the Aleutian Islands off Agattu Island ( Fig. 1 View FIGURE 1 ) at a depth of 881 m.

Etymology. The specific epithet refers to the long, attenuated body of the species.

Remarks. Allinectes attenuatus is known as a whole specimen only from the holotype ( Chernova et al. 2004), which was originally in poor condition ( Gilbert & Burke 1912a; Burke 1930) and has obviously deteriorated over time. Among other damage (e.g., stripped skin, broken fin rays) typical of snailfishes collected in the late 1880s and early 1900s, the dorsal fin is damaged, both pectoral fins are now broken, and the posteriormost vertebrae, including the caudal fin, are missing. Among unconfirmed published reports ( Chernova et al. 2004) of A. attenuatus is one of an otolith ( Stein & Fitch 1984). Despite searching institutions listed in the publication as well as other likely collections (i.e., CAS, USNM, LACM, SIO; D. Stein, pers. comm., 3 January 2024), I was unable to locate and examine the otolith or the specimen from which it was removed.

Burke (1930) described the dorsal fin as being slightly notched, with the anterior ray moderately elongate and longer than succeeding rays, a condition that was not noted nor illustrated in the original description by Gilbert & Burke (1912a: fig. 24). Now broken, the two anterior dorsal-fin rays must have been much shorter than the easily detected prominent rays in A. istiophorus , new species, A. busbyi , new species, and A. nanstanorum , new species, whose anteriormost rays are 31.5–103% HL.

Although morphometric comparisons are sometimes challenging among snailfishes because of their condition and more or less flaccid bodies, the characters that differentiate A. attenuatus from A. ectenes and the new species (e.g., body depth at anal-fin origin) are easily measured between clearly demarked bony points in the otherwise damaged types. Burke (1930) and later authors compared A. attenuatus with Careproctus homopterus , which differs in having short anterior dorsal-fin rays, a black stomach, and more dorsal- and anal-fin rays (dorsal-fin rays 55, anal-fin rays 49 vs. 48 and 40, respectively, in A. attenuatus ), as well as a smaller orbit and larger pelvic disk noted by Burke (1930).