Lestidium prolixum Harry, 1953

Ho, Hsuan-Ching, Tsai, Song-Yu & Li, Hsing-Hui, 2019, The barracudina genera Lestidium and Lestrolepis of Taiwan, with descriptions of two new species (Aulopiformes: Paralepididae), Zootaxa 4702 (1), pp. 114-139 : 134-136

Lestidium prolixum Harry, 1953

Figures 6 A–D; Tables 1–5 , 9–10

Lestidium prolixum Harry, 1953a:204 , figs. 25, 28 (Type locality: Kumano-Nada, off Shikoku, Japan, depth 200 fathoms). Post, 1972:150. Fukui & Ozawa, 2004:293.

Specimens examined. Collected from off Dong-gang, southwestern Taiwan, except as indicated: NMMB-P16330 (1, 225), Nan-fang-ao, Yilan, NE Taiwan, 20 Jul. 2010 . NMMB-P21908 (1, 259, stained), 1 Nov. 2014 . NMMB- P22468 (2, 267–267, stained), 30 Jan. 2015 . NMMB-P24622 (1, 264, stained), 17 Feb. 2016 . NMMB-P24634 (1, 261), 18 Feb. 2011 . NMMB-P25272 (1, 255), tail broken, 29 Mar. 2015 . NMMB-P25552 (1, 276), 6 Feb. 2017 . NMMB-P25761 (1, 235), 29 Mar. 2017 . NMMB-P30787 (1, 230), 16 Jul. 2017 . Other localities. Japan : NSMT-P67571 (1, 237), 30°25.46’N, 128°14.19’E, East China Sea, 500–512 m, otter trawl, 6 Nov. 2003 . NSMT- P67588 (1, 227), 28°59.78’N, 127°9.35’E, East China Sea, 350 m, otter trawl, 5 Nov. 2003 . NSMT-P75256 (1, 232), 37°35.71’N, 141°41.02’E, Pacific coast off Fukushima, Honshu, southern Japan, 277–284 m, trawl, 29 Oct. 2006 . NSMT-P79558 (1, 243) , NSMT-P79559 (1, 237), 37°36.8’N, 141°43.7’E, Pacific coast off Fukushima, Honshu, southern Japan, 306 m, trawl, 30 Oct. 2007 . KAUM-I. 86327 (1, head broken), KAUM-I. 86328 (head broken), KAUM-I. 86329 (1, 176), KAUM-I. 86330 (1, 162), KAUM-I. 86331 (1, 163), KAUM-I. 86332 (1, 173), KAUM- I. 86333 (1, 170), KAUM-I. 86334 (1, 168), KAUM-I. 86335 (1, 177), R/ V Kumamoto-maru, st. 54, 26°26.07’N, 124°07.49’E, East China Sea, 135–143, 17 May 2015 . KAUM-I. 88753 (1, 164), Each China Sea, 18 May 2015 .

Diagnosis. Lateral-line scales 145–158; anal-fin rays 31–33; vertebrae: prehaemal 36–41, prepelvic 35–38, predorsal 38–42, total 87–93; DFO slightly overlapped with pelvic fin to slightly behind tip of pelvic fin, D–V 3.8–5.4% SL and 18.4–25.5% V–A; gill chamber and branchial membranes uniformly blackish; large dots along upper margin of lateral line forming a wave-like boundary.

Description. Dorsal-fin rays 10; pectoral-fin rays 13–14; pelvic-fin rays 9; anal-fin rays 31–33. Vertebrae: prehaemal 36–41; caudal 50–53; prepelvic 35–38; predorsal 38–42; preanal 50–53; and total 87–93. Lateral line complete, running to the caudal-fin base, 35–37 scales before VFO, 39–42 before DFO, 54–57 before AFO, and 145–158 in total, 62–65 large ones, followed by 82–94 small ones. Gill rakers: 11–14 on upper limb (eipbranchial) and 30–39 on lower limb (17–21 on ceratobranchial+14–18 on hypobranchial).

Body elongate and slender, somewhat robust, strongly compressed, depth at pectoral fin 12–23 in SL. Caudal peduncle shorter than eye diameter; its depth 2.1–3.0% SL. Abdominal ridge well-developed with very low adipose fin; ventral adipose fin wall-developed along margin between anus and anal fin.

Head somewhat robust, moderately long and pointed, slightly triangular; its length 4.4–5.0 times in SL. Mouth terminal, moderately large, its gape extends to anterior margin of eye; lower jaw slightly upturned at tip. Eye large, its diameter 5.4–6.2 in HL. Seven infraorbital bones, first slender, the fifth and sixth well-expanded posteriorly, and the seventh small. A light organ between first and second infraorbitals. Interorbital space narrow and flat, its width 8.8–10.7 in HL. Four gill arches, all with gill filaments. The third and fourth arches mostly connected by membranes. Pseudobranch present, inside a deep pocket.

DFO slightly overlapped with posterior portion of appressed pelvic fin to slightly behind of tip of the fin and well behind middle of the fish, predorsal length 1.6–1.7 in SL. Pectoral fin at same level of posterior margin of gill cover, the uppermost ray at about same level of lower margin of eye. Pelvic fin well behind middle of the fish, prepelvic fin 1.7–1.8 in SL. Anal fin originating at posterior fourth of body, preanal length 1.3 in SL. Adipose fin above rear portion of anal-fin base.

Two or three fangs on upper jaw, followed by single row of small, retrose teeth, gradually smaller in posterior portion. Vomerine teeth absent. Two rows of fangs on lower jaw, gradually smaller posteriorly, those in outer row short and fixed; those in inner row long, each with a knife-like tip, and depressible. Two rows of fangs on each palatine, those in inner row much longer than those in outer row. Teeth on tongue small, arranged in single scattered row on each side. Gill rakers present on epibranchials, ceratobanchials and hypobanchiasl; shield shape, each with 3–5 small teeth. Teeth on pharyngeal arch slender, forming an oval patch with about 5 rows at middle.

Body devoid of scales, except for a single row of lateral-line scales originating from above pectoral-fin girdle and running to the caudal-fin base. Lateral-line scales slightly broader than its width, gradually smaller and becoming narrower posteriorly; 4 or 5 pores forming a cluster on each upper and lower margin of the scales.

Luminescent duct unbranched, well developed at ventral abdominal cavity, originating from below pectoral fin and running to anus.

Coloration. Body translucent when fresh, creamy white when preserved. Chromotophores on surface of first three infraorbitals, especially dense on the third. Dorsum largely blackish, not extending downward to upper broader of lateral line, a row of dots along upper margin of lateral line forming a continuous wave-like boundary. Pectoral fin mostly transparent, except for scattered chromotophores on the rays. Chromotophores on bases and rays of dorsal and anal fins and on base and first pelvic-fin ray. Abdomen ridge with broad blackish margin, black on either side of luminescent duct. Ventral adipose fin covered with scattered chromotophores. Branchiostegal rays with scattered chromotophores; branchiostgal membranes entirely black. Gill chamber and gill arches mostly black.

Size. Appear to be a large species with adults reaching 272 mm SL; by far the largest species among congeners found in Taiwan.

Distribution. Known from the type locality ( Japan) and newly recorded in Taiwan. In Taiwan, the specimens were collected by bottom trawl at depths 200– 500 m.

Remarks. Lestidium prolixium is the largest species among the congeners, and it has the most numerous lateralline scales, 147–158 (up to 160 in the type series; Harry, 1953a).

Figures

FIGRUE 6. Lestedium prolixum, NMMB-P25552, 276 mm SL. A. lateral view. B. lateral view of trunk showing origins of dorsal fin (above), pelvic fin (left) and anal fin (right). C. mid-trunk region showing the pigmentation, preserved. D. ventral view of head showing the coloration of gill cavity; arrow points to anterior end of abdomen luminous organ. Anterior to left.