Allinectes busbyi, Orr, 2025

Allinectes busbyi , new species urn:lsid:zoobank.org:act:5181EED7-E75E-4BE5-8B07-813960359260

Ardent Snailfish

Figures 1 View FIGURE 1 , 2A View FIGURE 2 , 3 View FIGURE 3 ; Tables 2 View TABLE 2 and 3 View TABLE 3

Holotype. SIO 94-198 About SIO , 120.0 mm, Aleutian Islands , Seguam Pass, 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

Diagnosis. Distinguished from all other species of Allinectes by a combination of its prominent protruding snout, moderately elongate anterior dorsal-fin rays, small orbit, and lower counts of vertebrae and median-fin rays. It is most similar to A. istiophorus , new species, from which it differs in its strongly protruding snout, shorter anterior dorsal-fin rays (vs. strongly elongate in A. istiophorus , new species) and smaller orbit (26.1% vs. 27.5–34.2% HL). Differing from A. curilanus in stomach dark (vs. dusky to lightly speckled in A. curilanus ), peritoneum black (vs. pale), and fewer vertebrae (48 vs. 53–59) and median-fin rays (dorsal 45 vs. 48–54; anal 38 vs. 42–49). Differing from A. nanstanorum , new species, in its strongly protruding snout (vs. rounded in A. nanstanorum , new species), caudal fin truncate (vs. dorsalmost caudal-fin ray longer and thicker), stomach dark (vs. pale), lighter body color, longer anterior dorsal-fin rays (vs. moderately elongate) and smaller orbit (26.1% vs. 27.1–31.8% HL). Similar also to A. attenuatus , known from only the holotype, but further differing in having fewer median-fin rays (dorsal 45 vs. 48 and anal 38 vs. 40, respectively, in A. attenuatus ), a deeper body at anal-fin origin (70.9% vs. 39% HL), longer pre-anal-fin length (38.5% SL vs. 32.5% SL), and anus closer to the disk (8.1% vs. 24.7% HL) and farther from anal-fin origin (65.9% vs. 29.4% HL). Further differing from A. ectenes in having peritoneum black (vs. pale in A. ectenes ), fewer vertebrae (48 vs. 54) and median-fin rays (45 vs. 48–51 dorsal-fin rays, and 38 vs. 44 anal-fin rays), deeper body at anal-fin origin (70.9% vs. 46.7–61.5% HL), and larger pelvic disk (40.2% vs. 27.6–28.3% 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 (21.8% vs. 26.9% SL), and anus closer to the pelvic disk (8.1% vs. 25.7% HL).

Description. Body elongate, slightly tapered, robust and rounded anteriorly, compressed posteriorly; depth at pelvic disk 76.3% HL; depth at anal-fin origin 70.9% HL. Head large, 21.8% SL, width 51.7% HL, broadly depressed, nape elevated. Snout broadly pointed, slightly longer than orbit, 114% OL, 29.9% HL. Snout tip projecting strongly anterior to lower jaw, 48.5% OL, projecting well forward of premaxilla. Mouth inferior; upper jaw 38.3% HL, maxilla extending to mid-orbit, oral cleft extending to anterior rim of orbit; mandible 42.2% HL. Premaxillary and mandibular teeth trilobed in 9 oblique rows of 8 teeth forming narrow bands. Orbit small, 26.1% HL, dorsal margin below dorsal contour of head, suborbital depth to upper jaw 11.5% HL, to lower jaw 23.4% HL; pupil round. Interorbital space convex, broad, fleshy distance 31.0% HL, bony distance 18.0% HL. Nostril single, on short tube at level with midorbit; nostril-tube length 14.7% OL.

Free neuromasts not evident. Gill opening small, 23.8% HL, upper margin at dorsal rim of orbit, extending ventrally to pectoral-fin ray 1. Gill rakers 7 ( Tables 2 View TABLE 2 , 3 View TABLE 3 ), short, robust, blunt, broad based.

Dorsal-fin rays 45 ( Tables 2 View TABLE 2 , 3 View TABLE 3 ), anteriormost rays elongate, ray 1 60.5% HL, longer than succeeding rays, followed by shorter rays 2–5, forming deep notch, followed by longer ray 6 and succeeding rays, anterior 3 rays deeply emarginate, 50–70% free from membrane. Anteriormost dorsal-fin pterygiophore inserted between neural spines 3 and 4. Pre-dorsal-fin length 22.9% SL.

Anal-fin rays 38 ( Tables 2 View TABLE 2 , 3 View TABLE 3 ), two anal-fin pterygiophores anterior to first haemal spine, each bearing single ray, tips of all rays not exserted. Anal-fin origin below vertebra 11 (caudal vertebra 1), pre-anal-fin length 38.5% SL.

Pectoral fin deeply notched, with 35 rays ( Tables 2 View TABLE 2 , 3 View TABLE 3 ). Upper lobe 83.5% HL, with 26 rays, extending well beyond anus to anal-fin origin, shorter than lower lobe, dorsalmost rays lengthening to rays 8–10, more ventral rays gradually shortening to shortest ray of notch. Lower lobe elongate, about equal to HL, 104.6% HL, with 9 rays, extending well beyond anus about 75% to anal-fin origin; dorsal rays lengthening to elongate rays, 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 75% 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 midorbit.

Pelvic disk moderate, length 40.2% HL, longer than wide, width 35.6% HL, anterior lobe developed, flat, distance from tip of snout to pelvic disk 12.2% SL. Anus below anterior part of dorsal fin, close behind pelvic disk, distance from disk 8.1% HL, distance from anal-fin origin 65.9% HL; distance from snout to anus 23.0% SL, 105.4% HL.

Caudal fin truncate. Principal caudal-fin rays 11, dorsal procurrent rays 2, ventral procurrent rays 1 (2 + 5/6 + 1). Caudal fin 60.9% HL. Dorsal-fin rays attached to caudal fin 30.8% CL; anal-fin rays, 37.7% CL. Depth at base of caudal fin 23.9% CL.

Vertebrae 48, precaudal 10, caudal 38 ( Tables 2 View TABLE 2 , 3 View TABLE 3 ). Pleural ribs 3, anteriormost small, others long and slender, present on vertebrae 8–10. Hypural plate composed of dorsal and ventral plates with no evident split.

Skin relatively thick. Pyloric caeca on left side of visceral cavity.

Coloration. Live color unknown. In preservation, body and fins pale; peritoneum black; orobranchial cavity dusky dark; stomach dark, intestines pale, pyloric caeca pale, and urogenital papilla pale.

Distribution. The only known specimen of Allinectes busbyi was collected in the Aleutian Islands northwest of Seguam Island ( Fig. 1 View FIGURE 1 ) at a depth of 458 m.

Life history. The specimen is a ripe female 120 mm with yolked eggs. Yolked eggs were 3.0 mm in diameter.

Etymology. The specific epithet is a patronym recognizing the contributions to the systematics of the Liparidae by Morgan S. Busby of the Alaska Fisheries Science Center, NOAA Fisheries. The common name refers to his enthusiasm for fishes in general and snailfishes in particular.

Remarks. The holotype and only known specimen of A. busbyi was collected in 1994 in the same haul as specimens of A. istiophorus , new species, and at the same station as the holotype of A. istiophorus , new species. Although somewhat damaged, it is immediately distinguished by its prominent protruding snout and large robust body, unlike all other individuals of A. istiophorus , new species. Like other members of Allinectes , its anterior dorsal-fin rays are elongate, but they are less so than in A. istiophorus , new species, with which it is most similar.

Among species of Careproctus , it is similar in general body morphology and preserved external color to C. pulcher Chernova, Thiel & Eidus, 2020 , but differs in having a black peritoneum (vs. pale in C. pulcher ), elongate anteriormost dorsal-fin rays (vs. anteriormost rays shorter than succeeding rays), and higher counts of vertebrae and anal-fin rays (vertebrae 48 vs. 46; anal-fin rays 38 vs. 35–36). The protruding snout and elongate body of A. busbyi is similar to Careproctus simus , which differs from it in having dark posterior fins and body (vs. an entirely pale body in A. busbyi ), pale peritoneum and stomach (vs. dark peritoneum and stomach), and more vertebrae (59–63 vs. 48) and median-fin rays (dorsal-fin rays 54–58 vs. 45, anal-fin rays 47–51 vs. 38).