Lycenchelys maculata Toyoshima, 1985

Pladdys, John, 2022, Taxonomic Review of the Rare Deep-sea Eelpout, Lycenchelys maculata (Pisces, Zoarcidae), Bulletin of the National Museum of Nature and Science. Series A, Zoology (London, England) 48 (4), pp. 215-227 : 216-223

Lycenchelys maculata Toyoshima, 1985

[Japanese name: Korobuchi-hebigenge]

( Figs. 2–7 ; Table 1)

Lycenchelys sp. : Toyoshima, 1984a: 293, pl.274-D (brief description with new Japanese name, Onahama); Toyoshima, 1984b: 307, pl.274-D (brief description, Onahama); Toyoshima, 1988a: 293, pl.274-D (brief description with new Japanese name, Onahama); Toyoshima, 1988b: 307 (brief description, Onahama)

Lycenchelys maculatus Toyoshima, 1985: 149 , figs. 8–9 (original description, Onahama); Hatooka, 1993: 904, unnumbered fig. (key, Onahama); Imamura, 1998: 31 (list, Onahama); Shinohara et al., 2009: 723 (list)

Lycenchelys maculata : Anderson, 1994: 117 (list); Hatooka, 2000: 1035, unnumbered fig. (key, Onahama); Hatooka, 2002: 1035, unnumbered fig. (key, Onahama); Anderson and Fedorov, 2004: 17 (list, Onahama); Shinohara and Anderson, 2007: 64 (key); Balushkin et al., 2011: 980 (list, Pacific Ocean off Kuril Islands and Japan); Hatooka, 2013: 1229, unnumbered fig. (key, Onahama); Kawarada et al., 2020: 19 (redescription, Pacific off Fukushima and Ibaraki prefec- tures and Kuril Islands)

Description. Counts and measurements are provided in Table 1.

Body elongated, cross section oval anteriorly, compressed laterally near tail. Snout length larger than eye diameter. Eye oval, not included to dorsal profile of head. Interorbital space nar- row, its width less than 1/2 eye diameter. Nostril single, its tube short, not reaching upper lip when depressed. Mouth subterminal. Posterior end of upper jaw reaching below eye. Labial lobe present in lower jaw. Teeth on jaws, vomer and palatine. Gill slit not reaching to lower end of pectoral fin base. Opercular flap present. Gill rakers short, triangular. Pseudobranch filaments present. Lateral line single, positioned ventrally, incomplete, terminating above middle of anal fin base. Cycloid scales covering nape, body, tail and basal half of vertical fins. Dorsal fin origin above pectoral fin base. Pectoral fin reaching to middle of abdomen. Pelvic fins present or absent.

Osteology and dentition. Suborbital bones 6: 1st bone large and long, articulating with palatine; others tubelike. Suborbital bone configura- tion L-shaped pattern (sensu Anderson, 1994). Supraorbital canal developed on nasal and frontal; postorbital canal on pterotic; temporal canal on parietal. Parietal small and squarish, both side bones separated by supraoccipital. Parasphenoid wing reaching mid-height of trigeminofacialis foramen, attached to frontal and pterosphenoid. Vomer with conical teeth ( Fig. 4C ). Posttemporal ventral ramus well developed. Maxilla long, slender; its posterior end slightly expanded. Premaxilla with developed ascending process, its alveolar process with conical teeth in single row ventrally ( Fig. 4C ). Groove supporting mandibular canal system developed on dentary and anguloarticular. Dentary with conical teeth dorsally; teeth arranged in 2 rows anteriorly and single row in middle and posteriorly. Hyomandibular with 2 articular heads for cranium dorsally, one for opercle posteriorly. Metapterygoid firmly attached to hyomandibular and symplectic posteriorly and to quadrate ventrally. Palatopterygoid series (mesopterygoid and ectopterygoid) slightly reduced. Palatine with conical teeth in single row ventrally ( Fig. 4C ). Preopercle largest and opercle 2nd largest in opercular bones. Preopercular foramina for 7th preoperculomandibular pore at mid-height and 8th below dorsal edge. Ceratohyal-epihyal articulation smooth. Four branchiostegal rays on ceratohyal, 1 on ceratohyal-epihyal junction, and 1 on epihyal. Lower pharyngeal teeth developed. Upper pharyngeals with 3 tooth patches, associated with gill arches 2–4. First epibranchial rod-like. Scapular not attached to coracoid. Postcleithrum single, thin, rod-like. Actinosts 4: uppermost smallest. Pelvis attached to inside of cleithrum, supporting 0–2 rays. First dorsal fin pterygiophore associated with 3rd vertebra. Epineurals and ribs present. First neural spine small.

Color when fresh based on color photographs of NSMT-P 109687 and KPM-NR 121359–121360. Ground color of head and body light grayish ( Fig. 2 ). Dorsal half of head dark brown with dark gray around eyes and in postorbital region. Occipital region slightly reddish brown. Head pores whitish on dorsal half of head. Black ocellus dorsally on opercle. Body with dark grayish irregular blotches dorsally and laterally but not on belly and anal fin base. Outer margin of dorsal fin dark brown. Upper lobe of pectoral fin dark near its base.

Color in alcohol. Head and body uniformly light to dark brownish. Outer margin of dorsal fin dark. Upper lobe of pectoral fin dark near its base. Branchial cavities light brown. Peritoneum dark brown. Dark irregular blotches present on head and body dorsally and laterally except for largest specimen (body color darkened) from Simushir Island ( Fig. 7A ) and the smallest specimen (body color faded) from Kakegawa ( Fig. 7J ), which lack prominent blotches. Some of specimens from Kuril Islands ( Fig. 7A–D ) with pale tail.

Distribution. Known from Pacific off Simushir and Urup islands and off Onahama (Fukushima Prefecture), Nakoso (Fukushima), Choshi (Chiba) and Kakegawa (Shizuoka) at depths of 200– 489 m.

Figures

Fig. 2. Fresh condition of Lycenchelys maculata. A, NSMT-P 109687, 150.8mm SL, off Onahama, Japan; B, KPM-NR 121356–121360, 32cm TL, off Onahama, photographs taken by Mr. Hajime Masuda.

Fig. 3. CT images of head and anterior body osteology in Lycenchelys maculata, NSMT-P 109687, 150.8mm SL. A, dorsal view; B, lateral view; C, medial view of right side (cross section); D, ventral view.

Fig. 4. CT images of head osteology in Lycenchelys maculata, NSMT-P 109687, 150.8mm SL. A, frontal view of left side; B, frontal view of ventral side; C, ventral view of upper half (cross section); D, dorsal view of lower half (cross section).

Fig. 5. CT images of osteology (A–C, F) and skin (D–E) in Lycenchelys maculata, HUMZ 71362, paratype, 279.5mm SL. A, dorsal view; B, lateral view of left side; C, medial view of right side (cross section); D, dorsal view; E, lateral view of left side; F, lateral view of right side. op—occipital pores; pmp—preoperculomandibular pores.

Fig. 6. CT images of pelvic girdle and fin rays in Lycenchelys maculata, HUMZ 71362, paratype, 279.5mm SL. A, ventral view of head and throat; B, ventral view of pectoral and pelvic girdles with pelvic fin rays; C, dorsal view of pelvic girdle with rays; D, rear view of pelvic girdle with rays.

Fig. 7. Alcohol-preserved specimens of Lycenchelys maculata. A, ZIN 46270 (Simushir Island); B, ZIN 46271 (Simushir Island); C–D, ZIN 46272 (Simushir Island); E, ZIN 46273 (Urup Island); F, ZIN 44945 (Nakoso, Fukushima Prefecture); G, NSMT-P 10929 (Choshi, Chiba Prefecture), H, NSMT-P 10930 (Choshi); I, NSMT- P 10931 (Choshi); J, NSMT-P 102466 (Kakegawa, Shizuoka Prefecture).