Luciobrotula polylepis, Wong & Lee & Chen, 2021

Wong, Man-Kwan, Lee, Mao-Ying & Chen, Wei-Jen, 2021, Integrative taxonomy reveals a rare and new cusk-eel species of Luciobrotula (Teleostei, Ophidiidae) from the Solomon Sea, West Pacific, European Journal of Taxonomy 750, pp. 52-69 : 58-63

Luciobrotula polylepis sp. nov.

urn:lsid:zoobank.org:act:E7C043DA-005E-494F-9E00-21454E6E61BA

Figs 3–4 ; Table 2

Diagnosis

Luciobrotula polylepis sp. nov. is morphologically distinct from all congeners by the following combination of characters: lateral line ending below 33 rd dorsal-fin ray; dorsal-fin rays 86, anal-fin rays 70, precaudal vertebrae 13, total vertebrae 50; gill rakers 17 (3 long rakers and 14 dentigerous plates); longest gill raker 2.1% SL; height of posterior margin of maxilla 3.2% SL; distance from the snout to end of lateral line 60% SL; one interorbital pore and four occipital pores.

Differential diagnosis

The new species is most similar to L. brasiliensis because both share the low number of vertebrae. It differs from L. brasiliensis by having a much longer lateral line (ending at the 33 rd dorsal-fin ray vs ending at the 2 nd dorsal-fin ray), a slightly more posterior position of the anal-fin origin (first anal ray below dorsal ray no. 22 vs first anal ray below dorsal ray no. 17), more pectoral-fin rays (32 vs 26), more gill rakers (17 vs 13–14), longer gill raker on first arch (2.1% SL vs 1.2% SL).

Luciobrotula polylepis sp. nov. differs from L. bartschi ( Figs 5–7 ) in having a slightly longer lateral line (ending at the 33 rd dorsal-fin ray vs the 18 th –26 th dorsal-fin ray) and narrower posterior margin of maxilla (3.2% SL vs 3.6–4.7% SL).

It differs from L. coheni by having more anal-fin rays (70 vs 59–65), fewer total gill rakers (17 vs 21–26), a more anterior anal-fin origin (anterior anal-fin ray below 17 th vertebra vs anterior anal-fin ray below 21 st –22 nd vertebrae), a narrower interorbital space (3.5% SL vs 3.9–5.6% SL), and a narrower posterior margin of the maxilla (3.2% SL vs 3.9–4.9% SL).

It differs from L. corethromycter by having fewer dorsal-fin rays (86 vs 91–96), fewer gill rakers (17 vs 18–21), and anterior position of the anal-fin origin (first anal-fin ray below the 17 th vertebra vs first analfin ray below the 20 th –22 nd vertebrae).

It differs from L. nolfi by having a slightly longer lateral line (ending at the 33 rd dorsal-fin ray vs ending at the 27 th –31 st dorsal-fin ray), slightly more anterior position of the anal-fin origin (first anal-fin ray below the 17 th vertebra vs first anal-fin ray below the 19 th –20 th vertebrae), smaller head (23.9% SL vs 24.5–28.0% SL), and relatively deeper body (16.3% SL vs 12.5–15.0% SL).

It differs from L. lineata by having a much longer lateral line (ending at the 33 rd dorsal-fin ray vs ending at the 2 nd dorsal-fin ray), fewer dorsal-fin rays (86 vs 92), more pectoral-fin rays (32 vs 26), shorter pelvic-fin rays (10.9% SL vs 15.0% SL) and longer gill raker on the first arch (2.1% SL vs 0.7% SL). A detailed comparison between the new species and other congeners is provided in Table 2 .

Along the COI gene, the following apomorphic sites are unique nucleotides from the only specimen of L. polylepis sp. nov. examined here; these nucleotide sites can be used for the molecular diagnosis of the species to differentiate it from L. coheni and L. bartschi examined in this study. Nos. 97 (C vs T), 120 (A vs G), 147 (G vs A), 177 (G vs A), 180 (C vs T), 198 (C vs T), 219 (T vs C), 225 (C vs T), 294 (C vs T), 321 (A vs C), 324 (G vs A), 330 (A vs G), 336 (A vs C), 348 (G vs A or C), 363 (G vs T or C), 369 (T vs C), 372 (A vs C or T), 375 (C vs T), 381 (G vs A), 387 (C vs T), 390 (T vs C), 405 (C vs T), 420 (A vs G or C), 426 (T vs C), 465 (A vs C or G), 477 (A vs G), 540 (A vs G), 555 (G vs A), 565 (T vs C), 597 (T vs C), 603 (T vs A), 615 (C vs A), 648 (T vs C), 682 (C vs A or G), 675 (C vs T), 684 (G vs A), 687 (T vs C).

Etymology

The name polylepis is derived from the Greek ‘ poly ’, meaning ‘many’ or ‘numerous’, and ‘ lepis ’, meaning ‘scales’, in reference to the much longer lateral line and therefore more lateral line scales compared with L. bartschi , the only congener distributed in the West Pacific.

Type material

Holotype

SOLOMON SEA • 168.4 mm SL, sample ID: PNG2363 ; Ainto Bay , SE of New Britain Island, Papua New Guinea, Solomon Sea , West Pacific , stn CP4334; 6°08′ S, 149°10′ E; 430–620 m depth; 6 May 2014; R/V ALIS; French beam trawl; MADEEP expedition; GenBank registration: MW218670 ; NTUM 11915 .

Description

Measurements and counts of the holotype given in Table 2 . Body elongate with tapering caudal portion, snout and head slightly depressed; eye small and round, horizontal eye diameter about half of snout length. Mouth large, oblique; upper jaw reaching a vertical through the posterior margin of orbit, posterior part vertically much extended, slightly protruding beyond lower jaw when mouth closed. Boomerang-formed vomer; palatine, and upper and lower jaw with many small, close-set, rather blunt teeth in several irregular rows; fang-like teeth absent in both jaws. One median and a pair of two large basibranchial tooth patches. Anterior nostril with low rim and placed midway between upper lip and posterior nostril, with small rounded flap rising from anterior rim. Posterior margins of preopercle, interopercle, and subopercle rounded, without spine. First gill arch with four finely dentigerous plates on upper branch, one long raker on the angle, and lower branch with two long rakers interspaced with 10 dentigerous plates ( Fig. 4D ); gill filaments ca 100, the longest about half as long as longest gill raker; pseudobranchial filament damaged, unavailable count.

Sensory pores are found all over head ( Fig. 4A–B ). Supraorbital with group of eight pores behind eye, five pores immediately above eye, and five small pores in a row on tip of snout, larger pore between flaps on tip of snout, and above each nostril, one interorbital pore, four occipital pores, six suborbital pores and four mandibular pores, 10 small pores close to lower jaw, between this row and mandibular having four small pores, and finally a row of six pores above posterior mandibular, two pores behind posterior end of maxilla, and preopercle with six pores.

Sagittal otolith is elongate and thin, about 2.5 times as long as high. Sulcus divided into ostium and cauda. Cauda is about ⅔ of ostium ( Fig. 4C ). Due to the damaged anterior rim, the presence of an ostial channel could not be ascertained.

Body, top of head, and opercle covered with small cycloid scales, with ca 72 scales in oblique line from origin of anal fin forwards and ca 111 scales from upper part of gill slit to base of caudal fin; single lateral line originating at upper angle of opercle and extending posteriorly in straight line placed about midway between midline and profile of body, ending below 33 rd dorsal-fin ray. Dorsal-fin origin above end of pectoral fin; anal-fin origin at about mid-body of fish, pectoral fin placed medially and pelvic fin reaching one third from base to anal fin.

Third neural spine pointed, length of first spine half as long as second spine ( Fig. 3C ), neural spines of posterior 10 pre-caudal vertebrae with blunt tips and broad bases, 4 th –11 th precaudal vertebrae with broad bases and depressed neural spines, 7 th –13 th precaudal vertebrae with parapophyses, and pleural ribs on 3 rd –6 th precaudal vertebrae. Epipleural ribs hard to observe.

Head brown; body brownish-yellow with bluish-brown abdomen ( Fig. 3A ). Dorsal, pectoral, anal, and caudal fins black. Color of preserved specimen similar to that of fresh specimens, the head and body uniformly brown with dark bluish-brown abdomen ( Fig. 3B ).

Distribution

Possibly endemic to waters off Papua New Guinea; the only known specimen was collected on the SE continental slope of New Britain Island, Papua New Guinea, at depths of 430–620 m ( Fig. 1 ).

Accompanying fauna

Monomitopus sp. and Glyptophidium lucidum Smith & Radcliffe, 1913 were the only two other ophidiids collected along with L. polylepis sp. nov., in addition to Epigonus atherinoides (Gilbert, 1905) ( Epigonidae Poey, 1861 ) ( Okamoto et al. 2018). The mud bottom living invertebrates collected from the same site included sea cradles, sea snails, sea stars, deep-sea barnacles, decapods (https://expeditions.mnhn.fr/campaign/madeep/event/cp4334#les_photos), and a recently described deep-sea spider crab, Tunepugettia corbariae Lee, Richer de Forges & Ng 2019 ( Epialtidae MacLeay, 1838 ) (Lee B.-Y. et al. 2019).

Figures

Fig. 3. Holotype of Luciobrotula polylepis sp. nov., 168.4 mm SL (NTUM 11915). A. Fresh specimen. B. Preserved specimen. C. Radiograph. Needle points to the lateral line end.

Fig. 4. Luciobrotula polylepis sp. nov., holotype (NTUM 11915). A. Dorsal view of sensory pores on head. B. Ventral view of sensory pores on head. C. Median and ventral view of right sagitta. D. First gill raker (left side).

Fig. 5. Luciobrotula bartschi Smith & Radcliffe 1913. Voucher specimen, 393.7 mm SL (NTUM 16627). A. Fresh specimen. B. Preserved specimen. C. Radiograph. Second needle points to the end of the lateral line.

Fig. 6. Luciobrotula bartschi Smith & Radcliffe 1913. Voucher specimen, 301.7 mm SL (ASIZP 0068164). A. Preserved specimen. B. Radiograph. Needle points to the end of the lateral line.

Fig. 7. Luciobrotula bartschi Smith & Radcliffe 1913. Voucher specimen, 181.6 mm SL (ASIZP 0063749). A. Preserved specimen. B. Radiograph. Needle points to the end of the lateral line. Arrows point to fused vertebrae.

Fig. 1. Distribution of Luciobrotula polylepis sp. nov. (red star) and L. bartschi Smith & Radcliffe 1913 (solid circles) based on specimens examined in this study.