Research Article |
Corresponding author: Tzu-Yung Lin ( plextorx0428@nkust.edu.tw ) Academic editor: Nina Bogutskaya
© 2023 Hsuan-Ching Ho, Tzu-Yung Lin.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Ho H-C, Lin T-Y (2023) Adult morphology and redescription of Lestidiops indopacificus (Ege, 1953), with comments on the features of related species (Teleostei, Aulopiformes, Paralepididae). ZooKeys 1160: 109-124. https://doi.org/10.3897/zookeys.1160.103110
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Two specimens representing the first known adults of Lestidiops indopacificus (Ege, 1953) are reported and described from Taiwan, and the validity and generic assignment of this species are confirmed. The origin of the pelvic fin directly below the dorsal-fin base shows that L. indopacificus belongs to the L. mirabilis species complex. It can be separated from its congeners by the position of the nostrils above the posterior end of the maxilla, the light body color with unevenly distributed melanophores in adults, and a distinct combination of meristic values and other morphological characteristics. New geographic records are reported for the two other current members of this species complex, L. mirabilis (Ege, 1933) and L. extremus (Ege, 1953). The diagnostic features that separate these three very similar species are discussed.
Biodiversity, biogeography, ichthyofauna, ichthyology, taxonomy
The barracudina genus Lestidiops was established by
Recently, two adult specimens of barracudina collected from off southern Taiwan were observed to have the pelvic-fin origin below the dorsal-fin base and no light organs or luminescent duct. They were initially identified as Lestidiops mirabilis (Ege, 1933) by the authors; however, both specimens had a much lighter body color compared to the uniformly dark brown to black body of specimens of L. mirabilis. More detailed examination has revealed that these two specimens represented the first adults specimens ever recorded of another, little-known species, Lestidiops indopacificus (Ege, 1953).
Lestidiops indopacificus, originally Lestidium indopacificum, was described based on juveniles collected from the Indian Ocean (
Lestidiops mirabilis, originally Paralepis mirabilis, was described by
Recently,
This paper provides the first detailed description of adult-stage L. indopacificus and a comparison with its most closely related congeneric species. Morphological and biogeographical data pertaining to newly found specimens of L. mirabilis and L. extremus are also presented.
Counts and measurements were made following
Morphometric data were not taken from specimens in poor condition, including those that had been bent or damaged. Abbreviations: DFO, dorsal-fin origin; AFO, anal-fin origin; VFO, pelvic-fin origin. D‒A, horizontal distance between the origins of the dorsal and anal fins (= preanal length minus predorsal length) and V‒A, horizontal distance between the origins of the pelvic and anal fins (= preanal length minus prepelvic length). PVLL, PDLL, and PALL are numbers of lateral-line scales before VFO, DFO, and AFO, respectively, TLL is the total number of lateral-line scales, including large and small scales. PVV, PDV, and PAV are numbers of vertebrae before VFO, DFO, and AFO, respectively, and PHV, CV, and TV are numbers of prehaemal, caudal, and total vertebrae, respectively.
Data used for comparison are taken from
Identity as Lestidiops indopacificus
The holotype of Lestidium indopacificum (
The original data for the holotype (31.0 mm SL) provided by
If the inferred position of the VFO in the holotype is accepted as standard, L. indopacificus shares this feature only with L. mirabilis and, by this alone, these two species can be separated from all other nominal congeners. According to
The three species reported below share a distinctive characteristic, namely, the VFO lies clearly behind the DFO, either below the dorsal-fin base or slightly behind that point.
Based on our examination, the three current members of the L. mirabilis complex can be separated from other species of Paralepidinae by having 80‒87 vertebrae in totalal, a single row of small teeth on the gill rakers (vs multiple rows of teeth, slender in many species), and a naked body except for the lateral-line scales (vs a body fully covered with scales). They can be separated from members of the L. atlanticum complex by the lack of a luminescent duct inside the abdominal cavity (vs a long duct extending to the gular region).
All other members of Lestidiops, regardless of their taxonomic validity, have the VFO situated slightly or well before the DFO.
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):
Lestidiops indopacificum
(Ege, 1953):
Lestidiops indopacificus
(Ege, 1953):
Holotype
:
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.
Morphometric and meristic data as provided in Tables
Morphometric data, as in % SL and % HL, of three species in the L. mirabilis complex. * including four specimens from
L. indopacificus | L. extremus | L. mirabilis | |||
---|---|---|---|---|---|
NMMB-P34421 |
|
n = 8* | |||
SL | 195 | 173 | 190 | 131.5‒276 | SD |
In % SL | |||||
Head length (HL) | 24.7 | 24.3 | 21.4 | 24.3 (22.7‒25.6) | 0.9 |
Body depth | 7.9 | 7.6 | 6.8 | 7.5 (7.1‒8.0) | 0.4 |
Predorsal length | 60.1 | 59.8 | 57.9 | 61.7 (59.9‒63.4) | 1.1 |
Prepelvic length | 60.8 | 60.7 | 63.2 | 61.9 (59.8‒63.6) | 1.4 |
Preanal length | 75.8 | 75.7 | 76.1 | 78.3 (75.9‒80.1) | 1.2 |
V‒A | 15.0 | 15.0 | 12.9 | 16.4 (15.2‒18.5) | 1.1 |
D‒A | 15.8 | 16.0 | 18.2 | 16.6 (14.5‒17.7) | 1.1 |
Eye diameter | 4.0 | 4.0 | 3.6 | 3.4 (3.1‒4.0) | 0.3 |
Interorbital width | 2.2 | 2.2 | 2.6 | 2.8 (2.5‒3.0) | 0.2 |
Snout length | 14.0 | 14.1 | 10.7 | 13.0 (12.3‒14.4) | 0.7 |
Head depth | 6.6 | 6.4 | 6.2 | 6.3 (5.6‒7.0) | 0.6 |
Head width | 3.4 | 3.5 | – | 3.8 (3.6‒4.1) | 0.2 |
Upper jaw | 12.1 | 12.1 | 10.4 | 12.4 (11.8‒13.1) | 0.4 |
Lower jaw | 16.2 | 16.9 | 13.6 | 16.2 (15.1‒17.3) | 1.0 |
Pectoral-fin length | – | – | 9.5 | 10.3 (8.3‒11.8) | 1.1 |
Anal-fin base | 17.5 | 17.7 | 17.9 | 15.5 (14.7‒16.3) | 0.6 |
Dorsal-fin base | 3.5 | 3.3 | 3.9 | 3.7 (3.4‒4.1) | 0.3 |
Pre-nostril length | 11.6 | 11.6 | 8.1 | 10.4 (10.2‒10.6) | 0.3 |
Caudal peduncle depth | 2.3 | 2.4 | – | 2.6 (2.4‒2.8) | 0.2 |
Caudal peduncle length | 6.1 | 6.6 | 5.6 | 4.3 (3.5‒5.2) | 1.2 |
In % HL | |||||
Pectoral-fin length | – | – | 44.2 | 42.2 (34.3‒47.1) | 4.6 |
Eye diameter | 16.2 | 16.6 | 17.0 | 14.0 (13.0‒15.6) | 0.9 |
Interorbital width | 8.9 | 9.0 | 12.3 | 11.2 (9.9‒12.7) | 1.0 |
Snout length | 56.6 | 58.0 | 50.1 | 53.1 (49.0‒56.2) | 2.4 |
Head depth | 26.8 | 26.1 | 28.7 | 26.4 (25.1‒27.6) | 1.2 |
Pre-nostril length | 47.1 | 47.5 | 37.8 | 41.5 | – |
Upper jaw | 49.0 | 49.6 | 48.4 | 50.7 (49.4‒52.2) | 1.1 |
Lower jaw | 65.4 | 69.4 | 63.6 | 66.3 (63.2‒67.9) | 2.7 |
Meristic data of three species of the Lestidiops mirabilis species complex. Counts of both sides provided when different. * including four specimens from
L. indopacificus | L. extremus | L. mirabilis | |||
---|---|---|---|---|---|
NMMB-P34421 |
|
|
n = 9* | ||
Dorsal-fin rays | 10 | 10 | 10 | 10 | 9‒10 |
Anal-fin rays | 30 | 30 | 31 | 30 | 28‒30 |
Pectoral-fin rays | 14 | 13 | 12 | 13 | 12‒14 |
Pelvic-fin rays | 10 | 10 | 10 | 10 | 9‒10 |
PVLL | 33 | 33/34 | 38 | 37 | 35‒40 |
PDLL | 32 | 32/33 | 34 | 32 | 36‒39 |
PALL | 47 | 48 | 51 | 50 | 51‒56 |
TLL (large) | 58/60 | 59/61 | 63 | 63/62 | 63‒67 |
TLL (small) | 9/6 | 7/9 | 8 | 5/7 | 8‒22 |
TLL | 67/66 | 66/70 | 71 | 68/69 | 73‒85 |
PHV | 34 | 35 | 41 | 41 | 36‒42 |
CV | 44 | 45 | 39 | 40 | 43‒45 |
PVV | 33 | 34 | 38 | 38 | 36‒39 |
PDV | 32 | 33 | 33 | 32 | 35‒38 |
PAV | 47 | 48 | 50 | 50 | 50‒55 |
TV | 80 | 80 | 80 | 81 | 81‒87 |
GR, epibranchial | 8 | 11 | 9 | 9 | 10‒15 |
GR, ceratobranchial | 21 | 21 | 15 | 16 | 20‒26 |
GR, hypobranchial | 13 | 12 | 10 | 9 | 12‒25 |
Total GR | 42 | 44 | 34 | 34 | 44‒61 |
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.
When fresh, body pale to light gray, somewhat translucent, unevenly covered with melanophores (Fig.
Close-up photos of Lestidiops indopacificus (NMMB-P34421, 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.
Juveniles widespread in the Indo-West Pacific from Taiwan to Australia and South Africa to French Polynesia (
Paralepis mirabilis Ege, 1933: 228 (type locality: Sulawesi Sea, western Pacific, 4°03'N, 123°26'E; holotype lost).
Lestidium mirabile
(Ege, 1933):
Lestidiops mirabilis
(Ege, 1933):
Non-types:
(not examined but with reliable identification). BMNH 1984.1.1.50 (1, 145), 8°45'S, 114°17'E, south of Java, Indonesia, eastern Indian Ocean (listed by
Species of Lestidiops with PVO below dorsal-fin base, anus slightly behind the base; anal-fin rays 28‒30; lateral-line scales: PVLL 35‒40, PDLL 36‒39, PALL 51‒56, TLL 63‒67+8‒22 = 73‒85; vertebrae: PHV 36‒42, PDV 35‒38, PVV 36‒39, PAV 50‒55, CV 43‒45, TV 81‒87; total gill rakers 44‒61. Adults with body uniformly dark brown to black, densely and evenly covered with melanophores; juveniles pale with broad, dark bands.
According to
The information on this species in Tables
The number of gill rakers also shows a large variation. The specimen from Suriname has 44 gill rakers in total (12 on the upper limb + 32 on the lower), whereas other individuals have 53‒61 gill rakers (10‒14 + 39‒51).
Photographs of two Lestidiops from Myanmar A L. extremus (Ege, 1953),
The only specimen reported from New Zealand (
Lestidium extremum
Ege, 1953: 136, fig. 29 (type locality: Molucca Passage, 0°18'S, 132°52'E [West Papua, Indonesia], ca 100 m depth).
Lestidiops extremus
(Ege, 1953):
Holotype
:
Non-types:
Species of Lestidiops with VFO clearly behind DFO and slightly behind posterior end of dorsal-fin base; anus well behind DFO; posterior end of maxilla extending nearly to vertical drawn through anterior margin of eye; lateral-line scales: PVLL 37‒38, PDLL 32‒34, PALL 50‒51, TLL 68‒71, including 62‒63 large + 5‒8 small scales; vertebrae: PHV 41, CV 39‒40, PVV 38, PDV 32‒33, PAL 50, TV 80‒81; gill rakers 9+25 = 34; anal-fin rays 30‒31. Adults uniformly black; juveniles with dark blotches and broad bands.
Type series from off West Papua, Indonesia, ca 100 m depth; adults collected from off southeastern Luzon Island, Philippines, at 760‒770 m depth.
This species was originally described from a type series consisting of three larvae from Indonesia, and the only previously known adult was reported from the Philippines by
The snout is quite slender in L. indopacificus, moderate in L. mirabilis, and rather stout in L. extremus. The VFO is slightly but clearly behind the dorsal-fin base in L. extremus, whereas it is under the dorsal-fin base in L. indopacificus and L. mirabilis (
There are 10 dorsal-fin rays in all three species, except that
Total gill raker counts for L. mirabilis are 44 (Atlantic specimen) or 53‒61 (Indo-Pacific specimens) versus 34 total gill rakers in two adults of L. extremus and 42‒44 in two adults of L. indopacificus. The gill rakers are quite closely spaced in L. mirabilis, widely spaced in L. extremus, and intermediate in L. indopacificus. On each gill raker there are usually three or four closely spaced teeth, which are quite long in L. extremus, only moderately so in L. mirabilis, and short in L. indopacificus.
Comparison of the proportional measurements of all three species in the L. mirabilis species complex (Table
As for meristic values (Table
It is notable that both adult specimens of L. indopacificus have their nostrils directly above the posterior end of the maxilla, which is different from the two other species (with nostrils situated well before the end of the maxilla), as well as from most other species of Lestidiops, although information on this is lacking for some species (
This study was supported by the National Museum of Marine Biology and Aquarium, Taiwan, the National Kaohsiung University of Science and Technology, Taiwan, and the Australian Museum, Sydney. Thanks go to P. Psomadakis (FAO) for collecting specimens and curatorial teams at