Lestidium rofeni, Ho & Graham & Russell, 2020

Ho, Hsuan-Ching, Graham, Ken & Russell, Barry, 2020, Three new species of the barracudina genus Lestidium (Aulopiformes: Paralepididae) from the Indo-West Pacific, Zootaxa 4767 (1), pp. 71-88 : 82-87

Lestidium rofeni sp. nov.

urn:lsid:zoobank.org:act:E117C340-DA0C-42EE-8007-18451C8B5D7A

Rofen’s Barracudina

Figs. 4C , 5C , 6 A–D, 7A–D, 8A–C; Tables 1–2

Holotype. NMMB-P28479 (245 mm SL), off Dong-gang , Pingtung, southwestern Taiwan, northern South China Sea, 30 Jan. 2018, collected from fish landing port.

Paratypes. Twenty-five specimens, 135–264. AMS I.36454-009 (2, 217–242), FSV Fishery Researcher 1, 13°09’N 124°02’E, Albay Gulf, Philippines, demersal trawl, 375 m, 23 Sept. 1995, coll. J. Paxton. AMS I.36464-004 (3, 247–264), FSV Fishery Researcher 1, 14°42’N 123°23’E, 250 km E of Manila, Philippines, demersal trawl, 440 m, 27 Sept. 1995, coll. J. Paxton. NMMB-P 24621 (1, 244), 5 Jul. 2016; NMMB-P 25548 (1, 143), 20 Jan. 2017; NMMB-P 25549 (1, 154), 20 Jan. 2017; NMMB-P 25550 (1, 172), 20 Jan. 2017; NMMB-P 25551 (1, 162), 10 Jan. 2017; NMMB-P 27926 (1, 248), 16 Jul. 2017; NMMB-P 27927 (1, 239), 16 Jul. 2017; NMMB-P 27931 (7, 135–148), 6 Dec. 2017; NMMB-P 28480 (1, 192), 30 Jan. 2018; NMMB-P 30875 (5, 151–183), 30 Jan. 2018; collected from near type locality.

Non-types. NMMB-P 16428 (1, 211), 28 Jan. 2012; NMMB-P 23851 (1, 193), 17 Feb. 2017; NMMB-P 23939 (3, 228–243), 20 Feb. 2016; NMMB-P 23988 (1, 244), 5 Mar. 2016; NMMB-P 24426 (1, 189), 17 Feb. 2016; NMMB-P 24624 (5, 140–169), 27 Jun. 2016; NMMB-P 24627 (4, 122–143), 27 Jun. 2016; NMMB-P 24632 (1, 207), 12 Jan. 2011; NMMB-P 24633 (1, 184), 25 May 2013; NMMB-P 25546 (5, 126–149), 4 Feb. 2016; NMMB-P 25547 (1, 181.5), 20 Jan. 2017; NMMB-P 25603 (1, 146.5), 21 Sep. 2015; NMMB-P 25761 (1, 235), 29 Mar. 2017; NMMB-P 26453 (1, 243), 23 Jun. 2017; NMMB-P 26586 (1, 199), 25 Apr. 2017; NMMB-P 28838 (1, 167), 27 Jun. 2016; NMMB-P 30028 (1, 250), Dong-gang, no date; NMMB-P 30786 (5, 180–184); NMMB-P 30792 (1, 151), out of NMMB-P 25553, 31 Mar. 2016; NMMB-P 30804 (16, 105-187); NMMB-P 30805 (26, 90–195); NMMB-P 30806 (2, 203-235), 27 Mar. 2018; all collected from near type locality.

Diagnosis. A species in the Lestidium prolixum species complex with a complete lateral line and a simple luminescent duct originating below opercle.; L. rofeni can be further distinguished from two other congeners in the species complex in having 30–33 anal-fin rays; prehaemal vertebrae 36–38 and total vertebrae 87–90; lateral-line ending at caudal fin base, with 123–139 scales; DFO clearly behind tip of adpressed pelvic fin; V–D 6.7–8.7% SL and 30.2–36.7% V–A; 5–7 lateral-line scales and 5–8 vertebrae between VFO and DFO; scattered melanophores away from upper margin of lateral line before VFO, entirely translucent on remaining section of lateral line; abdominal ridge with none or scattered melanophores.

Description. Dorsal-fin rays 10; pectoral-fin rays 13 (12–14); pelvic-fin rays 9; anal-fin rays 33 (30–33). Lateralline scales: prepelvic 35 (34–36); predorsal 41 (40–43); preanal 55 (54–57); total 125 (123–139). Vertebrae: prehaemal 36 (36–38); caudal 52 (50–53); prepelvic 35 (34–36), predorsal 41 (40–41); preanal 54 (54–56); and total 88 (87–90).

Body relatively elongate, slender and compressed; belly straight to slightly convex in profile; greatest depth of body at approximately anterior third of body, depth at pectoral fin 15 (15–17) times in SL. Caudal peduncle longer than eye diameter, its length 1.3–1.4 time eye diameter. Dorsal adipose fin small. A moderately constricted abdomi- nal ridge between head and pelvic fins. Ventral adipose fin well-developed along abdominal ridge and along the margin between anus and AFO. Anus at about tip of adpressed pelvic fin, below or slightly before DFO.

DFO slightly, but clearly, behind tip of adpressed pelvic fin ( Figs. 4C ) and mid-point of SL ( Fig. 6 ), predorsal length 1.6 (1.6). Pectoral fin level with posterior margin of gill cover, the uppermost ray at about same level as lower margin of eye. VFO well behind midpoint of SL, prepelvic fin 1.8 (1.8–1.9) in SL. Anal fin originating at posterior fourth of body, preanal fin length 1.3 (1.3) in SL. Anal-fin base 5.4 (5.4–5.9) in SL. Adipose fin above rear portion of anal-fin base.

Head relatively slender, slightly wider at opercle than body, its length 4.8 (4.6–5.3) in SL. Snout moderately long and pointed distally, its length 1.9 (1.9–2.1) in SL. Postorbital length about one-third of HL. Mouth terminal, moderately large, its gape extending to anterior margin of eye; lower jaw slightly upturned distally, with a small fleshy tissue at its tip. Eye moderately large, its diameter 6.3 (5.5–6.8) in HL. No light organ in front of eye; a luminescent duct at lower margin of orbit.

Interorbital space narrow, its width 9.7 (8.9–9.7) in HL, some straight ridges on top of head and snout. Upper jaw length 2.1 (2.0–2.1) in HL, posterior end of maxilla extending slightly less than half eye diameter before anterior margin of orbit. Two nostrils close together, well in front of posterior end of maxilla, about one eye diameter before eye. Sensory canals on snout, check, operculum, and jaws; numerous sensory pores on dorsal surface of snout and lower surface of lower jaw.

Opercle thin, with posterior margin bluntly pointed, its lower margin notched around base of pectoral fin. Gill membranes joined far forward, before a vertical from anterior margin of the eye, free from isthmus. Five gill arches, filaments presence on the first to fourth arches, absent on fifth. The fourth arch mostly connected to the gill wall by a membrane. Pseudobranchs present, inside a deep pocket above gill arches.

Two or 3 fangs on upper jaw, followed by bands of small and retrorse teeth along upper jaw, becoming gradually smaller posteriorly. Three fangs, either depressible or fixed, at front of lower jaw, followed by two rows of fangs on lower jaw, forming 6–8 tooth pairs; those in the inner row long and depressible with a knife-like tip, and those in the outer row much shorter, recurved and fixed. Vomerine teeth absent. Two rows of fangs on each palatine, anterior 3–4 teeth forming widely-spaced tooth pairs, those in the inner row long and depressible, and in outer row small and fixed; posterior portion of palatine with single row of small fixed teeth. One row of small straight, teeth on each side of tongue.

Gill rakers well-developed on epibranchial, ceratobanchial and hypobanchial of first gill arch; the rakers shield shaped, each with 2–4 small teeth and a narrow base. Rakers on epibranchial of first arch 12 (9–15), ceratobranchial with 19 (15–21), hypobranchial with 16 (11–17), total rakers 47 (39–49). Teeth on pharyngeal arch slender, forming an oval patch with about 5 rows at middle. Single row of small teeth on fifth ceratobranchial.

Body devoid of scales, except for a single row of lateral-line scales originating at above pectoral girdle and extending to the caudal-fin base. The anterior 67 (64–68) scales on the lateral line are clearly larger in size than the remainder, are slightly longer than high with slightly concave upper and lower margins, and gradually becoming smaller and narrower posteriorly. The posterior 58 (57–72) scales are distinctly smaller scales above posterior half of anal-fin base and behind. Row of 3–5 large pores on each margin of the larger scales, the first pore larger than the rest, and a pore on upper and lower end of these distinctly smaller scales.

A well-developed, unbranched, elongate luminescent duct, extending forward to well beyond the eye and backward along midventral line of ventral margin to anus.

Coloration. Color when fresh ( Figs. 6A, C, D , 8 A–C), body slightly translucent, dorsal fourth greyish but rather indistinct; dorsal surface of head and lower lips blackish; posterior portion above anal-fin base and behind silvery white; through the skin, upper abdominal cavity black with all peritoneal sections fused, the rest slivery white; all fins clear, except for the caudal fin slightly blackish. Narrow black sub-margin along abdominal ridge or not ( Figs. 5C , 7B , 8B )

Preserved specimens ( Figs. 6B , 7 A–D) with upper fourth of body covered by fine melanophores, the lower margin of these melanophores not overlapped with lateral line ( Fig. 5C ). Anterior third of upper margin of lateral line with scattered melanophores, entirely translucent on posterior portion. Very few melanophores or unpigmented on lateral sides between pelvic and anal fins. Lower margin of orbital blackish; surface of cheek below eye covered by melanophores; anterior half of jaws blackish; dorsal surface of skull and nape black. Pectoral fin translucent; base of dorsal, pelvic and anal fin blackish interiorly; scattered melanophores on anal-fin rays and branchiostegal rays. Membranes of branchiostegal region translucent in younger individuals, gradually becoming scattered blackish patches, but never as much as in L. prolixum and L. nigrorostrum . Luminous duct creamy yellow; peritoneal membrane melanophores alone lateral side of luminous duct inside the abdominal cavity. Abdominal ridge pale or with narrow dark submargin ( Figs. 5C , 7B ).

Size. The largest specimen examined is a 264 mm SL non-type.

Etymology. The species is named after Robert R. Rofen (previously R. R. Harry), former research director of George Vanderbilt Foundation, Stanford University, who contributed a lot of knowledge on paralepidid fishes.

Distribution. The species is currently known only from Taiwan and the Philippines, but is likely widespread in northwestern Pacific Ocean. Off southern Taiwan, smaller specimens were collected by mid-water trawl (<100 m depth) and larger specimens usually caught by demersal trawl (> 300 m), which may suggest the adults shift to deeper waters with growth/age.

Remarks. Lestidium rofeni , L. prolixum and L. nigrorostrum share similar body proportions, meristics and general appearance, and form a species complex. Lestidium rofeni is sympatric with L. prolixum in southern Taiwanese waters but can be separated from L. prolixum in having 123–139 total lateral-line scales (vs. 147–158 in L prolixum ); 57–72 (vs. 82–91) small scales along posterior portion of lateral line. The DFO is clearly behind the tip of adpressed pelvic fin in L. rofeni ( Figs. 4C , 7C ), whereas it overlaps or is just slightly behind the tip of the adpressed pelvic fin in L. prolixum ( Fig. 4B ). Associated with this character are: V–D 30.2–36.7% SL in L. rofeni (vs 18.4–25.5% SL); 5–7 lateral-line scales and 5–8 vertebrae between VFO and DFO in L. rofeni (vs. 3–5 [mainly 4 scales and vertebrae, respectively); and 3–5 more prehaemal than predorsal vertebrae in L. rofeni (vs. 1–3, mainly 1 or 2 vertebrae). Moreover, L. rofeni generally has light coloration, compared to similar size individuals of L. prolixum which are darker.

Lestidium rofeni differs from L. nigrorostrum in having 123–139 total lateral-line scales (vs. 142–157 in L nigrorostrum ) and body coloration is also different. The area along the lateral line of Lestidium rofeni is without pigmentation except for few scattered black dots above the lateral line, whereas in L. nigrorostrum , melanophores extend downward from the dorsum to the lateral line along its whole length. In L. rofeni , the abdominal ridge is pale or with a narrow blackish sub-margin ( Figs. 5C , 7B , 8B ; vs. abdomen with pale margin and a very broad black sub-margin, Figs. 3A , 5A ); the gill chamber is mostly translucent or, at most, with scattered dark patches (vs. mostly blackish); and the membranes of the branchiostegal region are without colour in young/small individuals, gradually developing scattered blackish patches with increasing age/size, but never to the extent of L. nigrorostrum .

Lestidium rofeni was likely misidentified as L. nudum in the northwestern Pacific Ocean. Both species have nearly identical vertebral formulae and body proportions. However, L. rofeni is clearly different from L. nudum in having a complete lateral line extending to the caudal-fin base, whereas that in L. nudum is incomplete, extending only to above the anterior third of anal-fin base; and the total lateral-line scales are 84–87, with 64–68 large scales, followed by 15–21 smalles scales in L. nudum . All specimens of L. nudum examined by us have the branchiostegal membranes and rays entirely black, whereas in L. rofeni the color ranges from entirely translucent to irregular black patches on the membranes. Because the black patches on the branchiostegal region develop with age/size in L. rofeni , more small specimens of L. nudum need to be examined to fully understand the development of pigmentation in that species.

Comparative materials. Lestidium atlanticum : listed in Ho et al. (2019a). Lestidium orientale : listed in Ho et al. (2019a). Lestidium prolixum : listed in Ho et al. (2019a); CSIRO H 6295-11 (1, 262), Taiwan; NMMB-P30959 (33, 253–268) and NMMB-P30960 (24, 255–275), off Dong-gang, 13 Mar. 2019. Lestidium nudum : listed in Ho et al. (2019a).

Figures

FIGURE 3. Lestidium nigrorostrum sp. nov., holotype, CSIRO H1159-16, 316 mm SL. A. Lateral view. B. Lateral view head. C. Dorsal view of head. D. Ventral view of head, arrow indicates the anterior end of luminescent duct. E. Lateral view tail region, arrow indicates the posterior end of lateral line.

FIGURE 4. Posterior region of trunk showing the fin position. A. L. nigrorostrum sp. nov., from the holotype. B. L. prolixum, NMMB-P25552, 276 mm SL. C. L. rofeni sp. nov., one of paratypes, catalog number unknown. Bars indicate DFO (upper), tip of pelvic fin (ventral left) and AFO (right).

FIGURE 5. Anterior trunk region showing the pigmentation.A. L. nigrorostrum sp. nov., from the holotype, arrow indicates the upper margin of lateral line.B. L. prolixum, NMMB-P25552, 276 mm SL, arrow indicates the dots along upper margin of lateral line. C. L. rofeni sp. nov. from the holotype, arrow indicates the unpigmented region above lateral line.

FIGURE 6. Lestidium rofeni sp. nov. A. Holotype, NMMB-P28479, 245 mm SL, fresh. B. preserved holotype. C. Paratype, NMMB-P27926, 248 mm SL, fresh. D. Paratype, NMMB-P27927, 239 mm SL, fresh.

FIGURE 7. Lestidium rofeni sp. nov., from the holotype. A. Lateral view of head. B. Anterior trunk region. C. Middle region of trunk.

FIGURE 8. Lestidium rofeni sp. nov., NMMB-P30805, 195 mm SL, fresh coloration, showing pigmentations in different body region. A. Lateral view of head. B. Anterior region of trunk, arrow points the clear abdominal ridge. C. Caudal region.