Uncisudis advena ( Rofen, 1963 )

Ho, Hsuan-Ching & Pogonoski, John J., 2025, First adult record of Uncisudis advena (Rofen, 1963) from northwestern Australia (Family Paralepididae), Zootaxa 5673 (3), pp. 424-430 : 426-427

Uncisudis advena ( Rofen, 1963)

English name: Alien Hooktooth Barracudina

Figure 1 ; Tables 1–2

Pontosudis advena Rofen, 1963: 4 (type locality: Gulf of Mexico, off Mississippi Delta, Louisiana, U.S A., western Atlantic, 28°58'N, 88°18'W, depth 445–545 fathoms [814–997 m]); Rofen, 1966: 443, fig. 156 (description).

Uncisudis advena ( Rofen, 1963) : Post, 1972: 156 (type catalog). Ozawa, 1986: 233 (larva; Japan); Ozawa in Okiyama, 1988: 250 (larva; Japan); Fukui & Ozawa 2004: 293 (listed). Prokofiev, 2017: 643 (Indian Ocean, 1 spec., 65 mm SL).

Material examined. CAS-SU 55575 , holotype, 28°58’N, 88°18’W, Gulf of Mexico , 27 Oct. 1960 . CSIRO H 3081- 03 , 220 mm SL, 18°43’S, 116°46’E, north of Nickol Bay, Northwest Shelf , Western Australia, coll. R Jackson , scampi net, 513 m (bottom), 30 Oct. 1991 .

Condition of specimen. The specimen is in good condition, but the abdominal region is badly damaged, and the pelvic girdle is lost. A fresh color photograph and radiograph film taken earlier show presence of a small pelvic fin, on which the following description is based. The head and teeth are complete. Rays of other fins are damaged, but the numbers are countable. The anus is situated slightly behind dorsal-fin base, based on a pore (cloaca) remaining at the end of a short gut and the position of the pelvic fin. There is a well-developed ventral adipose fin before anal-fin origin, originating immediately behind the anus. The pelvic fin origin is slightly behind a vertical through the dorsal-fin base in the radiograph. Pigmentation partly retained, with some fading in preservative. There is a lanternfish ( Myctophidae ) inside the stomach (also damaged).

Description. Morphometric and meristic data are presented in Tables 1–2 .

Body relatively short, compressed. Caudal peduncle long, about 1.5 times eye diameter. Ventral adipose fin not evidently developed on abdominal ridge or only rudimentary (based on remaining portion of abdominal region) but well-developed between margin of anus and anal-fin origin. Anus situated slightly behind a vertical through posterior end of dorsal-fin base.

Head, snout and jaws slender and pointed, body relatively short. Mouth large, terminal, its gape extending to about one eye diameter before eye when mouth fully opened; a skin fold originating at middle of snout and ending about vertical through anterior margin of eye; tip of lower jaw slightly upturned, with a blunt fleshy process. Eye small, situated at posterior third of head. No light organ in front of or on lower margin of eye. Interorbital space relatively narrow; some straight ridges on top of snout and irregular ridge on top of head. Posterior end of maxilla extending to about 0.8 eye diameter in front of the eye. Two nostrils directly above posterior end of maxilla, about 0.8 eye diameter in front of the eye. Numerous sensory canals on snout, cheek, operculum, and jaws; numerous sensory pores on dorsal surface of snout and lower surface of lower jaw.

Five gill arches, gill filaments present on first four arches. The fourth gill arch mostly connected to the gill chamber by a membrane. Pseudobranchs present on inner wall of gill cover, anterior half inside a deep pocket. Gill rakers present on epibranchial, ceratobranchial and hypobanchial; shield shaped, closely spaced, each with 9–11 small teeth, roughly arranged in a cluster. Teeth on pharyngeal arch slender, forming an oval patch with about 5 rows at middle. Short row of small teeth on fifth ceratobranchial on each side, forming a V-shaped pattern.

Dorsal fin situated at about middle of body (without head and caudal fin). Pectoral fin slightly behind a vertical through posterior margin of gill cover, its upper base approximately horizontal with lower margin of eye. A small pocket behind pectoral-fin base. Pelvic fin origin slightly behind a vertical through dorsal-fin origin ( Fig. 1C ) Anal fin originating slightly before posterior quarter of the fish. Adipose fin large, with a long base, situated above rear portion of anal-fin base.

Two small fangs at tip of upper jaw, followed by single row of numerous small retrorse teeth along upper jaw, gradually smaller on posterior portion, estimated more than 150 in number. Vomerine teeth absent. Four (right)/ two (left) either depressible or fixed fangs at front of lower jaw, followed by two rows of fangs on lower jaw forming 9/5 tooth pairs, those in inner row long, depressible, with a knife-like tip; those in outer row much shorter, fixed, curved backwards. Four widely-spaced tooth pairs on anterior portion of each palatine, those in inner row depressible and long, those in outer row small and fixed, posterior portion with single row of 8 small fixed, loosely arranged teeth. One row of 11 small straight teeth on each side of tongue.

Body smooth without scales, except for a single row of lateral-line scales originating from above pectoral girdle and running to above about posterior third of anal-fin base. Lateral-line scales as high as their width, gradually smaller and narrower posteriorly; row of 3 pores on each side of scale, the anteriormost pore largest; no pore on border of scales. Luminescent duct absent.

Coloration. When fresh ( Fig. 1A ), body light gray with dorsal surface of head and dorsum brown. Dense melanophores on snout and lips of lower jaw. Large silvery white patch on abdominal region covering black peritoneum. Posterior region of lateral body (above posterior 2/3 of anal fin base) light brown. In preservation, body overall brown with dorsum uniformly dark brown; broad band of scattered melanophores on abdominal ridge (from skin remaining); large, more or less scattered melanophores on entire lateral line, and gradually extending downward, to entire lateral sides behind dorsal-fin origin. Dense melanophores on snout and lips of lower jaw, scattered ones on rest of head. All fins, except for pelvic fin, covered with melanophores. Gill chamber mostly black, gill arches and filaments pale; mouth cavity pale. Peritoneal membrane uniformly black; stomach black. No trace of black blotches on body.

Distribution. Most records are from the Atlantic Ocean, with some scattered recorded in the Indian and Pacific Oceans (see https://www.gbif.org/species/2401570). Currently, all records from FishNet2 (https://fishnet2.net/) are from the northwestern Atlantic Ocean. Bathymetric range 813–887 m in the Gulf of Mexico ( McEachran & Fechhelm 1998); our specimen was taken from a scampi trawl with a bottom depth of 513 m.

Figures

FIGURE 1. Adult specimen of Uncisudis advena, CSIRO H 3081-03, 220 mm SL. A. Fresh. B. Close-up of head showing nostrils (arrowed) and end of maxilla (broken line). C. Close-up of tail showing DFO (upper arrow), VFO (lower left), AFO (lower left), and anus (broken line). Image reversed (right side originally photographed).