Lestidium orientale, Ho & Tsai & Li, 2019

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 : 131-134

Lestidium orientale sp. nov.

New English name: Oriental barracudina

Figures 5 A–E; Tables 1–5 , 9 –10

Holotype. NMMB-P30812 (162 mm SL), off Dong-gang , Pingtung, SW Taiwan, northern South China Sea, midwater trawl, 25 Jan. 2018 [from bycatch].

Paratypes. Thirty-nine specimens, 74–162 mm SL, collected from off Dong-gang, near the type locality: KAUM-I. 125200–125203 (4, 130–152), 25 Jan. 2018 . NMMB-P11220 (1, 157, stained), 12 Jan. 2011 . NMMB- P23823 (1, 167) , NMMB-P23824 (1, 162, stained) , NMMB-P23825 (1, 128, stained) , NMMB-P23826 (1, 131), 4 Feb. 2016 . NMMB-P25557 (7, 131–177, stained) , NMMB-P25559 (1, 157, stained) , NMMB-P25560 (1, 162, stained) , NMMB-P25562 (3, 142–147), 20 Jan. 2017 . NMMB-P30802 (18, 74–162), 15 Jan. 2018 .

Non-types. Collected from Dong-gang, near the type locality: NMMB-P17858 (1, 119, stained) . NMMB-P20913 (1, 122, stained) . NMMB-P25553 (22, 94–161, stained) . NMMB-P25554 (9, 149–121, stained) . NMMB-P25556 (10, 125–157, stained) . NMMB-P25558 (1, 159, stained) . NMMB-P23827 (1, 130, stained) . NMMB-P25546 (6, 126–150, stained) . NMMB-P24628 (9, 85–148, stained) . NMMB-P25845 (1, 132) . NMMB-P24626 (2, 105–134, stained) . NMMB-P30789 (1, 135) . NMMB-P30801 (11, 95–145) . NMMB-P30811 (1, 146, stained).

Diagnosis. A species of Lestidium with light organ duct extending to beyond anterior margin of eye. It is most similar to Lestidium atlanticum and can be distinguished by having relatively more prehaemal vertebrae (37–40 vs. 36–37), a shorter snout (snout length 9.7–10.4 vs. 10.4–11.5% SL), shorter jaws (upper jaw 8.6–10.1 vs. 9.9–11.3% SL; lower jaw 11.9–13.7 vs. 13.5–14.8% SL) and relatively deep head (head depth 31.2–33.9 vs. 27.6–31.5% HL).

Description. Dorsal-fin rays 10; pectoral-fin rays 12–14 (mainly 13); pelvic-fin rays 9; anal-fin rays 26–30 (mainly 27–28); lateral-line complete, running to the caudal-fin base, 35–37 scales before VFO, 34–36 before DFO, 52–54 before AFO, and 109–126 in total, 56–60 large ones, followed by 55–77 small ones. Vertebrae: prehaemal 37–40; caudal 41–44; prepelvic 34–37 (35–36); predorsal 33–36 (34–35); preanal 51–54; and total vertebrae 79–83. Gill rakers: 8–13 on upper limb (epibranchial) and 26–40 on lower limb (13–20 on ceratobranchial+11–22 on hy- pobranchial).

Body stout, compressed, depth at pectoral fin 11–15 in SL. Caudal peduncle shorter than eye diameter; its depth 1.9–2.9% SL. Abdominal ridge well-developed with low adipose fin; ventral adipose fin wall-developed along margin between anus and anal fin.

Head relatively stout and blunt, triangular in lateral view, its length 4.5–4.9 times in SL. Mouth terminate, moderately large, its gape extends to anterior margin of eye; lower jaw slightly upturned at tip. Eye large, its diameter 4.6–5.5 in HL. Seven infraorbital bones, first slender, the fifth and sixth well-expanded, the seventh small. No light organ around the eye. Interorbital space narrow, its width 8.1–9.5 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 at about same vertical or slightly before the vertical of VFO, also slightly posterior to middle of the fish, predorsal length 1.7–1.8 times 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 of middle of the fish, prepelvic length 1.6–1.7 in SL. Anal fin originating slightly behind posterior fourth of body, preanal length 1.2–1.3 in SL. Anal-fin base 5.3–6.9 in SL. Adipose fin above rear portion of anal-fin base.

Two or three fangs on upper jaw, followed by single row of small, stout retrose teeth. 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 rows on each side. Gill rakers present on epibranchial, ceratobranchial and hypobranchial; shield shape, each with 1–3 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; 2–3 (mostly 3) pores on each side of lateral-line scales before the dorsal fin.

Luminescent duct well developed at ventral abdominal cavity, unbranched, originating from below the end of maxilla and extending to the anus.

Coloration. Body translucent when fresh, creamy white when preserved. Chromotophores on 4th and 5th infraorbital bones; top of head blackish. Anterior half of both jaws covered with chromotophores. Upper fourth of body covered with grayish chromotophores, extending to upper margin of lateral-line scales. Posterior fourth of body blackish with a broad middle silver band. Dorsal-fin rays and bases with black pigments. Pigments on anal-fin rays, absent on the fin base. No chromotophores on abdominal region. Scattered pigments around cleithrum and inner surface of gill cover.

Size. Appear to be a small species with largest adult examined at 167.0 mm SL.

Etymology. The specific name “ orientale ” means from the Eastern, in referring to the distribution around northwestern Pacific Ocean.

Remarks. Lestidium orientale sp. nov. is closely similar to L. atlanticum in that the luminescent duct extending forward below the posterior end of maxilla and VFO at about same vertical or slightly behind the vertical of DFO; whereas L. prolixium and L. nudum have the duct extending to below opercle only and DFO clearly behind a vertical of VFO. It differs from L. bigelowi in lacking light organs on lateral and ventral surfaces of body.

Lestidium orientale sp. nov. differs from L. atalnticum (restricted to the Atlantic population in present study) in having 37–40 (mainly 38–39) prehaemal vertebrae (vs. 36–37, mainly 37); snout length 9.7–10.4% (vs. 10.4– 11.5%) SL or 45.6–49.8% (vs. 49.7–50.8%) HL; upper-jaw length 8.6–10.1% (vs. 9.9–11.3%) SL or 40.9–48.4% (vs. 45.1–50.0%) HL; lower-jaw length 11.9–13.7% (vs. 13.5–14.8%) SL or 58.1–62.6% (vs. 62.0–65.2%) HL; relatively deep head 6.6–7.1% (vs. 6.3–6.7%) SL or 31.2–33.9% (vs. 27.6–31.5%) HL; and a different COI gene sequence (K2P distance = 0.050 –0.057).

The meristic data provided by Ege (1953) were divided into several geographic regions. He provided a broad range of meristics, i.e., 75–87 total vertebrae and 35–41 preheamal vertebrae, which is broader than most paralepidids. However, his data for Atlantic specimens are 80–83 total vertebrae (n=44) and 36–38 (mainly 37) preheamal vertebrae (n=22), wihch agree with our observation ( Tables 4–5 ). His data of specimens taken from the Indo-west Pacific Ocean can be further divided into high vertebra populations (83–87 total vertebrae), moderately high vertebra populations (79–83), and low vertebra population (75–80). Our specimens fit to Ege’s moderately high vertebra population and may be same with that. Moreover, we also recognized specimens from Taiwan and Australia with high vertebral counts as an undescribed species. We are not able to examine Ege’s specimens and the low vertebra population is still unknown. Further investagation is required.

Figures

FIGURE 5. Lestidium orientale sp. nov. A. holotype, NMMB-P30812, 162 mm SL, preserved; bars indicate origins of dorsal fin (above), pelvic fin (left) and anal fin (right). B. NMMB-P23823, paratype, 167 mm SL. C. NMMB-P23824, partype, 162 mm SL. D. close-up of head, from holotype. E. close-up of mid-trunk showing the pigmentation.

Tables

TABLE 9. Morphometric data of four Lestidium species. Negative values means that VFO is behind DFO.

	Lt. atlanticum		Lt. orientale sp. nov.			Lt. nudum	Lt. prolixum
	Non-types		Holotype	Selected types		Non-types	Non-types
SL (mm)	104–181 (n=8)		162	131–177 (n=15)		224–247 (n=3)	225–276 (n=19)
%SL	Mean (Range)	SD		Mean (Range)	SD	Mean (Range)	Mean (Range)	SD
Head length	22.2 (20.8–23.1)	0.8	20.6	21.1 (20.3–22.2)	0.6	21.8 (21.1–22.5)	21.1 (19.8–22.6)	0.7
Head depth	6.5 (6.3–6.7)	0.2	6.6	6.9 (6.6–7.1)	0.2	6.3 (6.2–6.5)	6.0 (5.6–6.4)	0.2
Pectoral fin	7.6	-	7.0	7.0 (7.0–7.1)	0.0	7.9 (7.9)	7.2 (6.5–8.3)	0.7
Predorsal	59.6 (58.7–60.4)	0.6	58.6	58.7 (57.7–59.9)	0.6	60.8 (60.5–61.1)	61.4 (59.5–62.7)	0.9
Prepelvic	58.5 (57.7–59.7)	0.7	59.9	59.5 (57–61.1)	0.7	54.2 (53.4–54.9)	57.1 (55.2–58.5)	0.9
Preanal	78.8 (77.8–79.9)	0.8	77.8	78.4 (77.8–79.2)	0.5	75.5 (74.9–75.9)	77.1 (76.4–77.9)	0.5
V–A	20.0 (18.7–21.2)	0.9	17.9	18.9 (17.8–21.1)	0.8	21.3 (21.0–21.4)	20 (19.2–21.2)	0.6
V–D	0.9 (0.6–1.2)	0.3	[-1.2]	[-0.8] ([-1.3] –[-0.7])	0.3	6.6 (5.8–7.7)	4.3 (3.8–5.4)	0.5
Eye diameter	3.9 (3.5–4.2)	0.2	4.0	4.0 (3.9–4.4)	0.1	3.7 (3.4–3.9)	3.6 (3.4–4.0)	0.2
Snout length	11.1 (10.4–11.5)	0.4	9.8	10.0 (9.7–10.4)	0.3	11.3 (11.3)	10.6 (10–11.2)	0.4
Interorbital	2.5 (2.2–2.8)	0.2	2.3	2.4 (2.3–2.5)	0.1	2.4 (2.4)	2.2 (2.0–2.3)	0.1
Upper jaw	10.4 (9.9–11.3)	0.5	9.3	9.3 (8.6–10.1)	0.4	10.5 (10.1–10.8)	9.7 (9.2–10.6)	0.4
Lower jaw	14.3 (13.5–14.8)	0.5	12.2	12.8 (11.9–13.7)	0.5	14.1 (13.3–14.6)	13 (12.2–13.7)	0.4
Body depth	7.2 (6.7–7.6)	0.5	7.5	7.6 (7.1–8.0)	0.3	6.9 (6.4–7.4)	6.5 (4.3–8.1)	0.7
% Head length
Head depth	29.4 (27.6–31.5)	1.4	32.2	32.5 (31.2–33.9)	0.9	29.0 (27.6–29.7)	28.3 (26.7–29.9)	0.9
Eye diameter	17.6 (15.2–20.4)	1.6	19.5	19.1 (18.1–21.5)	0.7	16.9 (15.3–18.0)	17.2 (16.0–18.6)	0.7
Snout length	50.1 (49.7–50.8)	0.4	47.6	47.6 (45.6–49.8)	1.0	51.8 (50.2–53.7)	49.9 (47.8–51.7)	1.1
Interorbital	11.4 (10.2–13.4)	1.0	11.3	11.3 (10.6–12.3)	0.5	11.0 (10.7–11.3)	10.3 (9.4–11.4)	0.5
Upper jaw	46.6 (45.1–50.0)	1.8	44.9	44.1 (40.9–48.4)	1.8	48.3 (48.0–48.7)	45.9 (43.9–48.2)	1.2
Lower jaw	64.2 (62.0–65.2)	1.1	59.3	60.8 (58.1–62.7)	1.3	64.5 (63.2–65.2)	61.4 (59.8–63.0)	1.1
% V–A
V–D	4.4 (3.1–6.5)	1.4	--	--		31.0 (27.7–35.8)	21.5 (18.4–25.5)	2.3