Lestidiops distans ( Ege, 1953 )

Lestidiops distans ( Ege, 1953) View in CoL

Figures 2A View FIGURE 2 , 3A‒D; Tables 1‒2 View TABLE 1 View TABLE 2

Lestidium distans Ege, 1953:95 View in CoL , 119, fig. 19 (type locality: off west coast of Africa, 10°21′N, 17°59′W, depth about 30 meters). Maul, 1962:527, fig. 2 (description of adult).

Lestidiops distans ( Ege 1953) View in CoL : Rofen, 1966:301 (re-assigned to Lestidiops View in CoL ). Post, 1972:146 (type catalog).

Specimens examined. Holotype. ZMUC P2316994 View Materials , bad condition (39.5 mm SL in original description), 10°21′N, 17°59′W, off Guinea-Bissau, west coast of Africa , ca. 30 meters (100 meters wire out) GoogleMaps . Additional specimens: SAIAB 66073 About SAIAB (4, 207‒221), 8°50′S, 12°55′E, off Angola, 308‒343 m, 14 Mar. 2002. SAIAB 64896 About SAIAB (1, 207), 7°22′S, 12°09′E, 364 m, bottom trawl, 22 Mar 2001. SAIAB 66012 About SAIAB (2, 207‒216), 9°12′S, 12°42′E, off Angola, 259 m, bottom trawl, 13 Mar. 2002. SAIAB 64909 About SAIAB (1, 216), 8°14′S, 12°46′E, off Angola, near surface, hook and line, 15 Mar. 2001. SAIAB 64332 About SAIAB (1, 217), 11°13′S, 13°31′E, off Angola, 326.5 m, bottom trawl, 7 Mar. 2001. SAIAB 66083 About SAIAB (14, 207‒228), 8°28′S, 12°53′E, off Angola, 308‒309 m, bottom trawl, 16 Mar. 2002. MNHN 1987-1631 About MNHN (2, 234‒237), off Senegal, 14°01′1.2″N, 17°31′1.2″W, 330 m, May 1979. HUMZ 148539 View Materials (1, 210), 19°44′12″S, 11°56′54″E, off Namibia, 333 m, 17 Feb. 1995, trawl net. HUMZ 148595 View Materials (1, 213), 18°50′48″S, 11°19′12″E, off Namibia, 598‒600 m, 3 Mar. 1995, trawl net. HUMZ 148596 View Materials (1, 220), 18°50′48″S, 11°19′12″E, off Namibia, 598- 600 m, 3 Mar   GoogleMaps , 1995. HUMZ 145446‒145450 View Materials (5, 123‒136), 22°18′S, 12°55′E, off Namibia, 335 m, trawl net, 21 Oct. 1995.

Description of holotype. The holotype (ZMUC P.2314994) is in rather poor condition. There are 11 dorsal-fin rays and 26 anal-fin rays remaining (28 in original description). Lateral line unclear due to poor condition. There are ca. 36 myotomes before VFO, ca. 40 before DFO, ca. 59 before AFO, with total number uncertain. Posterior end of maxilla terminates slightly behind anterior margin of eye; nostrils at posterior fourth of snout, anterior margin of anterior nostril at about midpoint of maxilla, ca. 0.3 eye diameter before anterior margin of eye. Eye diameter about 2.2 in snout length. Gill rakers not developed.

Ventral adipose fin well developed on ridge between anus and AFO and on abdominal ridge (between pectoral and pelvic fins), the latter is not as large as former. DFO slightly but clearly behind VFO; DFO well before midpoint of V‒A; anus slightly behind tip of pelvic fin, approximately below the penultimate dorsal-fin ray. Peritoneal sections not available due to long-term preservation. Anterior two pairs of palatine teeth longer than posterior ones (but may not be fully developed due to the young ontogenetic stage). Trunk and distance between anus and AFO relatively long. No light organ in front of and below the eye; no tract of luminescent duct inside abdominal cavity.

Diagnosis. A species of Lestidiops with lateral line complete, extending to caudal-fin base; body moderately slender; DFO slightly behind VFO; anus clearly behind DFO and below about middle of dorsal-fin base; dorsal fourth of body dark brown, covered with dense melanophores; scattered melanophores on lateral line and abdominal ridge; gill chamber dark; anal-fin rays 25‒28; TV 81‒84; TLL 123‒145.

Description. Morphometric and meristic data are provided in Tables 1‒2 View TABLE 1 View TABLE 2 . Dorsal-fin rays 10‒11; pectoral-fin rays 13‒14 (12 in Maul, 1962); pelvic-fin rays 9‒10; anal-fin rays 25‒27 (26‒28 in Ege, 1953). Lateral-line scales: PVLL 32‒35, PDLL 36‒39, PALL 53‒57, TLL 123‒145, with 58‒67 large + 63‒81 small scales. Vertebrae: PVV 34‒36, PDV 37‒39, PHV 37‒39, AV 55–57, CV 43‒45, P and TV 81‒84. Gill rakers 12‒15 on epibranchial, 14‒17 on ceratobranchial, 9 on hypobranchial, and total 35‒41 (15+15+7 = 37 in Maul, 1962).

Body elongate, rather compressed, body depth at pectoral fin 12.7‒15.7 times in SL. Caudal peduncle moderately long, its length 1.4‒1.8 times eye diameter and 1.5‒2.0 in HL. Ventral adipose fin very weakly developed along abdominal ridge between pectoral and pelvic fins, slightly better developed on margin between pelvic and anal fins. Anus located above tip of adpressed pelvic fin, slightly but clearly behind DFO and situated below anterior half of dorsal-fin base, as well as in front of midpoint of V‒A.

Head relatively strong and moderately long, its length 4.2‒4.7 in SL; head depth 3.2‒3.7 in HL; snout blunt, moderately long, its length 2.1‒2.3 in HL. Mouth terminal, moderately large, with gape extending well before eye; lower jaw slightly upturned at tip, with small distal tab of fleshy tissue. Eye large, its diameter 5.4‒6.6 in HL; anterior and posterior adipose eyelid present; no light organ around eye. First suborbital slender, the fifth and sixth expanded posteriorly, and the seventh small. Interorbital space narrow, its width 7.7‒10.7 in HL; some straight ridges present on top of head and snout. Posterior end of maxilla extending slightly but clearly to in front of anterior margin of eye. Two nostrils located well anterior to posterior end of maxilla, about 1/3 of the maxillary length before the tip and one eye diameter in front of eye. Numerous sensory canals on snout, cheek, operculum and jaws; numerous sensory pores on dorsal surface of snout and lower surface of lower jaw.

Gill filaments present on all four gill arches. Fourth arch mostly connected to gill chamber wall by membrane. Pseudobranchs present within deep pocket.

DFO well behind midlength of fish and well behind VFO, predorsal length 1.6 in SL. Dorsal-fin base short, 4.8‒5.9 in HL. Pectoral-fin base slightly behind posterior margin of gill cover, upper end of fin base slightly below a horizontal drawn through lower margin of eye; a small pocket behind fin base. Pectoral-fin length 2.4‒3.1 in HL. VFO slightly but clearly behind DFO, pre-pelvic fin length 1.7‒1.8 in SL. A small axial scale present posterior to pelvic-fin base. Anal fin originating in posterior fourth of body, pre-anal length 1.2‒1.3 in SL. Anal-fin base short, 6.0‒ 7.4 in SL. Adipose fin small, above rear portion of anal-fin base.

One to three small fangs at tip of upper jaw, followed by single row of numerous small, retrorse teeth, these gradually becoming smaller on posterior part of jaw. Vomerine teeth absent. Two depressible fangs at front of each lower jaw, followed by two rows of fangs arranged in 8‒10 widely-spaced pairs; those in inner row long with knifelike tip and depressible; those in outer row much shorter, recurved and fixed, slightly embedded in tissue. Two rows of fangs on each palatine, anterior teeth forming 3‒5 widely-spaced tooth pairs, those in outer row long and depressible, those in inner row small and fixed; these fangs followed by single row of small, widely-spaced fixed teeth on posterior part of jaw. Two rows of small, straight teeth on surface of tongue.

Gill rakers present on epibranchial, ceratobranchial and hypobranchial of each gill arch, shield-shaped, each with row of 3‒5 short teeth on a broad base. Single row of long and pointed teeth on each fifth ceratobranchial, both meet anteriorly forming a V-shape; teeth on pharyngeal arches long and pointed, well-spaced, forming a long oval patch, with about three rows in middle.

Body scaleless except for row of lateral-line scales originating from above pectoral girdle and running to caudal-fin base. Lateral-line scales wider than high, becoming gradually smaller and narrower posteriorly; anterior scales, running to anterior portion of anal fin, clearly larger than those behind. These large scales bearing an irregular row of 3‒4 (mostly 3) small pores on upper and lower margins; the small scales with a single pore on their upper and lower ends.

Luminous organs absent.

Coloration. Upper fourth of the fish dark brown, densely covered by tiny melanophores, extending downward to upper border of lateral line on anterior third of body. Dorsal melanophores gradually located more distantly from the lateral line posteriorly on flank. Lateral line covered by many scattered melanophores, leaving the trunk largely pale without any melanophores below lateral line. Dorsal surface of head, snout and anterior portions of jaws dark brown to blackish. Outer surface of gill cover largely pale, with only scattered melanophores on upper portion and cheek. Gill chamber dark brown; mouth cavity pale, without melanophores. Isthmus and abdomen ridge loosely covered by melanophores. Lateral side of posterior fourth of the fish, except for dorsum, evenly covered by melanophores. Pectoral fins pale, except for some inner melanophores on upper rays. Pelvic fins pale except for some melanophores on inner rays and on base of fins. Dorsal fin and anal fin mostly covered with melanophores. Adipose fin and caudal fin densely covered by melanophores, darker at bases. Peritoneum black. Fresh colors unknown.

Remarks. Lestidiops distans was originally described based on specimens collected off the west coast of Africa ( Guinea-Bissau). The original drawings clearly show the VFO is slightly in front of DFO and the anus is below the dorsal-fin base, either on anterior or posterior halves, closer to the middle of the fin base. Maul (1962) reported an adult individual of L. distans collected from off Dakar ( Senegal). Despite some minor differences, our specimens agree with Maul’s (1962) description ( Tables 1‒2 View TABLE 1 View TABLE 2 ), especially the complete lateral line which is a rare condition in Paralepididae , with about nine species ( Lestidium , Lestidiops and Macroparalepis ) known to exhibit this character (Ho, pers. data). The position of the anus was not able to be ascertained in Maul’s specimen, but in our specimens the anus situated below about the midpoint of the dorsal-fin base, which is consistent with the types.

Among congeners, Lestidiops ringens ( Jordan & Gilbert, 1880) from the northern Pacific Ocean is the only other species that has a complete lateral line extending to the caudal-fin base, however, there are still multiple species that currently lack adult information. It can be separated from L. distans by having DFO well behind VFO (vs. slightly behind in L. distans ) and anus well before DFO (vs. anus below dorsal-fin base).

Lestidiops distans is also similar to Lestidiops pacificus ( Parr, 1931) from the northeastern Pacific Ocean with regard to the position of the dorsal and anal fins. However, L. distans has a complete lateral-line running to the caudal-fin base and the anus is located below the midpoint of the dorsal-fin base, whereas L. pacificus has an incomplete lateral line running to between above the anal-fin base and the anus right behind posterior end of dorsal-fin base.

Although there are other species with DFO slightly behind VFO, in these species the anus is situated more anterior, either slightly before or closer to the DFO, and can be separated from L. distans . See below for names of these species.