Lestidiops indopacificus (Ege, 1953)

Ho, Hsuan-Ching & Lin, Tzu-Yung, 2023, Adult morphology and redescription of Lestidiops indopacificus (Ege, 1953), with comments on the features of related species (Teleostei, Aulopiformes, Paralepididae), ZooKeys 1160, pp. 109-124 : 109

Lestidiops indopacificus (Ege, 1953)

Figs 1 , 2

Lestidium indopacificum Ege, 1953: 120, fig. 26 (type locality: off India, Indian Ocean, 1°45'N, 73°03'E, ca 100 m depth).

Lestidiops indopacificus (Ege, 1953): Post 1972: 148 (type catalog).

Lestidiops indopacificum (Ege, 1953): Rofen 1966: 301 (presumably in Lestidiops , maybe related to L. mirabilis ).

Lestidiops indopacificus (Ege, 1953): Paxton et al. 1989: 246 (Australia, probably misidentification); Nakabo 2000: 368 (Ryukyus, juveniles only); Fukui and Ozawa 2004: 293 (list); Mundy 2005: 203 (larvae); Gomon 2008: 267 (Australia, misidentification of other Lestidiops ).

Material examined.

Holotype: ZMUC P2329237, in poor condition, 31.0 mm SL in original description. Adult specimens: NMMB-P34421 (2, 173- 195 mm SL), off Dong-gang, Pingtung, southwestern Taiwan, ca 300 m depth, 30 Jul. 2020.

Diagnosis.

Species of Lestidiops in the L. mirabilis species complex with the VFO under dorsal-fin base and anus farther posteriorly; dorsal portion of body and lateral line covered with melanophores, but large unpigmented areas present on lower portions of head and abdomen; lateral-line scales: PDLL 32-33, PVLL33-34, PALL 47-48, TLL 66-70; vertebrae: PDV 32-33, PVV 33-34, PAV 47-48, PHV 34-35, CV 44-45, TV 80; total number of gill rakers 42-44 (based on adult specimens). Juveniles without dark blotches or bands.

Description.

Morphometric and meristic data as provided in Tables 1 and 2 . Dorsal-fin rays 10; pectoral-fin rays 13-14; pelvic-fin rays 10; anal-fin rays 30. Lateral-line scales: PDLL 32-33, PVLL 33-34; PALL 47-48; 66-70 in total, with 58-61 large scales and (in rear portion) 6-9 small scales. Vertebrae: PDV 32-33, PVV 33-34, PAV 47-48, PHV 34-35, CV 44-45, 80 in total. Gill rakers: 42-44, with 8-11 on upper limb (epibranchial) and 33-34 on lower limb, including 21 on ceratobranchial + 12-13 on hypobranchial.

Body moderately long, strongly compressed, depth at pectoral fin 12.7-13.2 times in SL. Caudal peduncle short, its length 1.5-1.6 times eye diameter. Ventral adipose fin very weakly developed along abdominal ridge between pectoral and pelvic fins, better developed on margin between pelvic and anal fins. Anus situated above tip of appressed pelvic fin (smaller specimens with anus slightly before fin tip), distance from VFO to anus about 3.5-4.0 times in V-A.

Head moderately slender, long-triangular, its length 4.0-4.1 in SL; snout slender and pointed anteriorly, its length 1.7-1.8 in HL. Mouth terminal, moderately large, its gape extending to about 1.5 times eye diameter in front of eye. Lower jaw slightly upturned at tip, with small distal tab of fleshy tissue. Eye small, its diameter 6.0-6.2 in HL. No light organ around eye. First suborbital bone slender, fifth and sixth bones expanded posteriorly, and seventh small. Interorbital space narrow, its width 11.1-11.2 in HL; some straight ridges present on top of head and snout. Two nostrils located directly above posterior end of maxilla, latter extending to point about 2/3 eye diameter in front of eye. Numerous sensory canals on snout, check, 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 membranes. Pseudobranchs present, their anterior halves included in a deep pocket.

DFO slightly in front of VFO, predorsal length 1.7 in SL. Pectoral-fin base behind posterior margin of gill cover, upper end of fin base slightly below horizontal drawn through lower margin of eye; no small pocket behind fin base. VFO directly under dorsal-fin base, pre-pelvic fin length 1.6 in SL. No axial scale behind pelvic-fin base (probably lost during trawling). Anal fin originating in posterior fourth of body, pre-anal length 1.3 in SL. Dorsal adipose fin over rear portion of anal-fin base, its base length about equal to eye diameter.

Two or 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. One or two fangs (either depressible or fixed) at front end of each lower jaw, followed by two rows of fangs arranged in about 6 pairs (more teeth arranged irregularly on right jaw of larger specimen); those of inner row long with knife-like tip and depressible; those in outer row much shorter, curved, and fixed, slightly embedded in tissue. Two rows of fangs on each palatine with anteriormost teeth arranged in 4 widely spaced pairs, those in outer row long and depressible, those in outer row small and fixed; single row of small, widely spaced, fixed teeth on posterior part of palatine. One row of small, straight teeth on each side of tongue.

Shield-shaped gill rakers present on epibranchial, ceratobranchial, and hypobranchial parts of each gill arch, each raker with 3-5 (rarely fewer) small teeth on broad base, these teeth barely extending upward beyond margin of gill arch. Teeth on pharyngeal arch short, arranged in oval patch with about 4 rows in middle. Single row of small teeth on fifth ceratobranchial.

Body scaleless, except for single row of lateral-line scales extending from above pectoral girdle to point above approximately two-thirds length of anal-fin base. Lateral-line scales slightly longer than wide, gradually becoming smaller and narrower posteriorly; 2 large pores on each upper and lower corner of most scales and 1 pore at front and 1 pore on each upper and lower corners of those scales on about posterior third of lateral line.

Luminescent duct absent.

Coloration.

When fresh, body pale to light gray, somewhat translucent, unevenly covered with melanophores (Fig. 1A, B ), and with abdomen bright white. Dorsal fourth of body densely covered with tiny melanophores; slightly larger melanophores beneath extending to lateral line and further downward, gradually becoming scattered; lower third of abdomen pale with large unpigmented areas. Dense melanophores on dorsal surface of head, anterior snout and jaws, and gular region; rest of head pale, with scattered melanophores except in large unpigmented areas on cheek and operculum. Inner surface of operculum pale with large black patch; mouth cavity pale. Abdominal ridge covered with dense melanophores (fewer and scattered in small specimens). Pectoral, dorsal and pelvic fins pale, with scattered melanophores; anal fin covered with dense melanophores except for the paler basal region; caudal fin covered with dense melanophores. When preserved, body light yellow in general, with pigmentation pattern similar to fresh condition (Figs 1C, D , 2A-D ). Peritoneal membranes and stomach black; intestine pale.

Distribution.

Juveniles widespread in the Indo-West Pacific from Taiwan to Australia and South Africa to French Polynesia ( Ege 1953). Adults known only from two specimens collected from off southwestern Taiwan by bottom trawl at an estimated depth of around 300 m based on other fishes collected in the bycatch.

Figures

Figure 1. Adults of Lestidiops indopacificus (Ege, 1953), NMMB-P 34421 A, C 195 mm SL B, D 173 mm SL A, B fresh, photo by C. - N. Teng C, D preserved.

Figure 2. Close-up photos of Lestidiops indopacificus (NMMB-P 34421, 173 mm SL), left side with anterior to left, showing pigmentation and positional details of various structures A head, with arrow pointing to the nostrils B anterior trunk, arrow point to abdominal ridge C posterior trunk, with bars pointing to DFO (upper), VFO (lower left), and AFO (lower right) D tail, with arrow pointing to end of lateral line.