Allinectes, Jordan & Evermann, 1898

Genus Allinectes

Allurus Jordan & Evermann, 1896: 452 (subgenus; type species Careproctus ectenes by original designation; monotypic; objectively invalid; preoccupied by Allurus Förster [Hymenoptera] and by Allurus Eisen [Oligochaeta]).— Schmidt, 1950: 193 (synonym of Careproctus).— Stein 1978: 10 (synonym of subgenus Allinectes).— Chernova et al. 2004: 51 (genus-group name).

Alldurus Jordan & Evermann, 1898: 2131 (lapsus calami, corrected to Allurus on p. 2866).

Allinectes Jordan & Evermann, 1898: 2866 (replacement name for Allurus).— Burke 1930: 8 (elevated to genus for A. ectenes).— Stein 1978: 10 (subgenus).— Chernova et al. 2004: 51 (genus-group name).— Orr et al. 2019: 25 (genus-group name).

Allinectis: Andriashev, 2003: 33 (misspelling).— Schmidt 1950: 193 (synonym of Careproctus View in CoL ).— Kido 1988: 193 (misspelling).

Type species. Allinectes ectenes ( Gilbert, 1896)

Other included species.

Allinectes attenuatus ( Gilbert & Burke, 1912a)

Allinectes busbyi new species

Allinectes curilanus ( Gilbert & Burke, 1912b)

Allinectes istiophorus new species

Allinectes nanstanorum new species

Allinectes pycnosoma ( Gilbert & Burke, 1912b)

Diagnosis. Species of the Liparidae distinguished from all other species by having elongate, moderately to deeply emarginate anterior dorsal-fin rays 1 and 2, followed by shallow to deep notch in both sexes, teeth trilobed, vertebrae 47–59, cephalic pores 2-6-7-2, nostril single, and pseudobranchs absent.

Description. Body elongate, deepest at dorsal-fin origin, slightly tapered, compressed posteriorly. Head moderately small, less than 30% SL. Mouth small, horizontal. Teeth trilobed. Premaxillary tooth plates matching mandibular tooth plates. Diastema absent at symphyses of upper and lower jaws. Orbit small to large, dorsal margin below dorsal contour of head; pupil round. Nostril single.

Pores of cephalic lateralis system of moderate size, pore pattern 2-6-7-2, chin pores paired. Interorbital pore absent.

Gill opening small, extending ventrally to dorsal rays 1 or 2 of pectoral fin or entirely above pectoral-fin. Opercular flap angular. Gill rakers 4–9, short, blunt. Branchiostegal rays six. Pseudobranchs absent.

Dorsal-fin rays 42–54, anteriormost rays more or less elongate, moderately to deeply emarginate, followed by shorter rays forming shallow or deep notch, tips of more posterior rays not exserted; anterior rays uniserial and unsegmented, more posterior rays biserial and unsegmented; all rays simple. Anteriormost dorsal-fin pterygiophore inserted between neural spines 2 and 3 or 3 and 4, bearing single small ray.

Anal-fin rays 37–49, all rays biserial, segmented, and simple; one to three anal-fin pterygiophores anterior to first haemal spine, each bearing single ray. Anal-fin origin below vertebrae 13–14 (caudal vertebrae 2–3).

Pectoral fin with 28–39 rays; strongly notched. Upper lobe, with 21–30 rays, extending well beyond anus to anal-fin origin or slightly beyond, dorsalmost rays lengthening to rays 6–10, more ventral rays gradually shortening to shortest ray of notch. Lower lobe with 6–10 rays, dorsal rays lengthening to longest rays, more ventral rays gradually shortening to ventralmost ray near pectoral symphysis. Rays of notch slightly more widely spaced than rays of lobes, more widely spaced ventrally. Insertion of lowermost pectoral-fin ray below orbit.

Pelvic disk round to slightly longer than wide, flat.

Principal caudal-fin rays 10–12, dorsal procurrent rays 1–3, ventral procurrent rays 0–2 (1–3 + 5–6/5–6 + 0–2). Membrane of posterior dorsal-fin rays attached to caudal fin at shorter distance than anal-fin rays.

Skin naked, prickles absent.

Vertebrae 47–59, precaudal 9–11, caudal 37–49. Pleural ribs 1–3, anteriormost small when 3, others long and slender, present on vertebrae 9–10 or 8–10 (9–10). Single epural present.

Distribution. Species of Allinectes are distributed across the North Pacific, from the Sea of Okhotsk, off Sakhalin Island and the Kuril Islands, throughout the Aleutian Islands, and into the southern Bering Sea at depths of 117 to 1172 m ( Fig. 1 View FIGURE 1 ).

Etymology. Allinectes is derived from the Greek ἄλλος, meaning “another” and νηκτός, meaning “swimmer.”

Remarks. The subgenus Allinectes (a replacement name for Allurus ) was erected by Jordan & Evermann (1896) without a diagnosis for its sole member Careproctus ectenes , presumably because of its distinct general body morphology as presented by Gilbert (1896) in his original description. Burke (1930) further noted its distinctiveness, indicating that especially with having the pyloric caeca absent or reduced, the combined characters of dentition, depressed head, and projecting snout might warrant placing it in a new genus. Although he referred C. ectenes to genus Allinectes in the methods section for his 1930 revision of the Liparidae , he later referred it to Careproctus in the species account and other sections.

Key to species of Allinectes

1A. Peritoneum black................................................................................... 2A

1B. Peritoneum pale or dusky............................................................................ 5A

2A. Anterior dorsal-fin rays slightly to moderately elongate, less than 50% HL; stomach pale.......................... 3A

2B. Anterior dorsal-fin rays moderately to strongly elongate, 60% HL or longer; stomach dark......................... 4A

3A. Anal-fin rays 37–38; head slightly depressed, depth at nape 45–55% HL; head narrow, width 40–50% HL; vent closer to pelvic disk than anal-fin origin.............................................................. Allinectes nanstanorum Bering Sea , 860–1172 m

3B. Anal-fin rays 40; head deep, depth at nape 67% HL; head broad, width 60% HL; vent midway between pelvic disk and anal-fin origin.............................................................................. Allinectes attenuatus Aleutian Islands, Agattu Island, 882 m

4A. Snout strongly protruding; anterior dorsal-fin rays moderately elongate, 60% HL..................... Allinectes busbyi Aleutian Islands, Seguam Island, 458 m

4B. Snout rounded, not strongly protruding; anterior dorsal-fin rays strongly elongate, greater than 60% HL................................................................................................... Allinectes istiophorus Aleutian Islands , 117–762 m

5A. Peritoneum dusky; pyloric caeca 6–7, thick and short......................................... Allinectes curilanus Kuril Islands, Simushir Island, and Aleutian Islands, 240–471 m

5B. Peritoneum pale; pyloric caeca absent, filamentous, or more than 10.......................................... 6A

6A. Pectoral fin with strong notch and elongate lower rays,>50% HL; pyloric caeca absent or filamentous; vertebrae 54; anal-fin rays 44; snout tip slightly to strongly protruding.............................................. Allinectes ectenes Aleutian Islands, Unalaska Island and Bowers Bank, 494–640 m

6B. Pectoral fin with shallow notch and short lower rays, 33% HL; pyloric caeca about 17, short, blunt; vertebrae 49; anal-fin rays 39; snout tip blunt, not protruding....................................................... Allinectes pycnosoma Kuril Islands, Simushir Island, 419 m