Bathyuroconger parvibranchialis ( Fowler, 1934 )

Smith, David G., Ho, Hsuan-Ching & Tashiro, Fumihito, 2018, Eels of the genus Bathyuroconger in the northwestern Pacific, with descriptions of four new species (Anguilliformes: Congridae), Zootaxa 4454 (1), pp. 147-167 : 161-162

Bathyuroconger parvibranchialis ( Fowler, 1934)

English name: Small-gill large-toothed conger

Figs. 1 , 4 , 8C , 9A, C ; Tables 2, 3

SilveSterina parvibranchialiS Fowler, 1934:275 , fig. 35 (Butung [Buton] Strait, Indonesia, 5°35'00"S, 122°20'00"E, Albatross station 5648, depth 559 fathoms).

Bathyuroconger parvibranchialiS ( Fowler, 1934) : Smith, 1999:1686. Ho et al., 2015:145.

Bathyuroconger vicinuS (non Vaillant, 1888): Hatooka, 2002:232 (in part).

Materials examined. Indonesia: USNM 92346 (1, 645), holotype, 5.58°S, 122.33°E, Buton Strait, North Island , Sulawesi , Flores Sea, 1022 m, Albatross sta. 5648, 16 Dec. 1909 . USNM 93370 (1, 525), paratype, 3.33°S, 120.61°E, Gulf of Boni, Olang Point, Sulawesi, Gulf of Boni , 900 m, Albatross sta. 5657, 19 Dec. 1909 . Japan: NSMT-P 65442 (1, 394), 36.56°N, 141.20°E to 36.51°N, 141.14°E, off Ibaraki Pref., 509‒589 m, 25 Oct. 2002 . Philippines: BSKU 15687 (1, 656), BSKU 15688 (1,715), 8.35°N, 118.33°E, 738 m, Sulu Sea off Palawan Is., 27 May 1972 . USNM 93371 (1, 590), paratype, 10.2°N, 125.07°E, Sogod Bay, southern Leyte Island, Limasaua Island , Bohol Sea, 918 m, Albatross sta. 5202, 10 Apr. 1908 . USNM 93373 (1, 610), paratype, 9.38°N, 123.71°E, between Siquijor and Bohol Islands, Balicasag Island, Negros Oriental, Bohol Sea , 717 m, Albatross sta. 5527, 11 Aug. 1909 . USNM 93374 (1, 595), paratype, 8.28°N, 124.05°E, northern Mindanao and vicinity, Camp Overton Light, Misamis Occidental, Bohol Sea , 924 m, Albatross sta. 5513, 7 Aug. 1909 . USNM 93375 (1, 514), paratype, 8.26°N, 123.95°E, northern Mindanao and vicinity, Camp Overton Light, Misamis Occidental, Bohol Sea , 750 m, Albatross sta. 5511, 7 Aug. 1909 . USNM 93378 (1, 288), paratype, 13.75°N, 120.78°E, China Sea off southern Luzon, Sombrero Island , Batangas, 432 m, Albatross sta. 5111, 16 Jan. 1908 . Taiwan: ASIZP 66181 , 285 mm, CD321, South China Sea , 954 m, 19 Aug. 2005 . ASIZP 63794 , 695 mm, CD 193, 821 m, off Dong-gang, South China Sea, 29 Aug. 2002 . ASIZP 63789 , 640 mm, CD194, off Dong-gang, South China Sea, 507 m, 29 Aug. 2002 .

Temporary identification. ASIZP 66196 , 210 mm, off Suao, NE Taiwan, 339 m, 13 Jun. 2005.

Diagnosis. A species of Bathyuroconger with very small gill opening, its width 1.8‒9.0% of head length; gill opening separated from pectoral fin base by a greater distance than its width; head length 1.4‒1.7 times in trunk length, 35.2‒40.9 %PAL; predorsal length 12.6‒14.5 %PAL, trunk length 59.1‒64.8 %PAL. Preanal lateral-line pores 39‒47. Preanal vertebrae 43‒48; precaudal vertebrae 52‒60; total vertebrae 181‒189; MVF 9‒46‒185. Adults with body uniformly blackish, whereas juveniles are pale with rows of small melanophores.

Description. Measurements in %TL: PAL 33.3‒37.1, PDL 12.6‒14.5, HL 12.9‒14.7, TR 20.4‒22.7, DA 3.5‒5.2. In % PAL: PDL 36.3‒40.9, HL 37.4‒40.9, TR 59.1‒62.6, DA 14.3‒17.7. In % HL: S 23.3‒30.7, E 8.5‒18.6, IOW 10.8‒19.6, UJ 35.6‒41.1, GO 1.8‒9.0, IB 16.1‒32.3, PL 24.2‒41.9. Pores: PDLL 6‒8, PPLL 5‒8, PALL 39‒47, SO 3‒4, IO 5, POM 10, ST 1. Vertebrae: PDV 7‒10, PAV 43‒48, PCV 52‒60, TV 181‒189.

Body moderately slender, cylindrical anteriorly, gradually tapering and compressed posteriorly. Trunk short, truck length 1.4‒1.7 times head length. Tail thin but not filamentous, anus at about anterior third of total length. Dorsal and anal fins confluent with caudal, dorsal fin begins over base of pectoral fin, anal fin begins immediately behind anus; pectoral fin moderately well developed. Head large, rounded, deeper than body, jaws nearly equal. Snout short and blunt, rounded in dorsal view, about 2‒3 times eye diameter. Eye moderately small, over posterior part of upper jaw, posterior margin approximately over rictus; interorbital space relatively broad, its width greater than eye diameter. Anterior nostril a short tube, at front of snout; posterior nostril in front of mid-eye, a simple pore. Gill opening small, located anteroventrally to pectoral fin, its upper end below level of lower pectoral-fin base; distance from gill opening to fin base 2 or more times greater than diameter of gill opening.

Head pores moderate in size, not greatly enlarged and slit-like. Supraorbital pores 3: first pore at tip of snout, opening downward, second pore larger, above and behind first, in front of anterior nostril; third pore above anterior nostril; one specimen with an extra pore behind the third; no pores on interorbital space. Infraorbital pores 5, along upper jaw; first directly behind anterior nostril; second between anterior and posterior nostrils; third between anterior margin of eye and posterior nostril; fourth below posterior part of eye; fifth behind rictus; no pores behind eye. Preoperculomandibular pores 10; 7 on mandibular section and 3 on preopercular, the last one at about level of first lateral-line pore. One median supratemporal pore, anterior to level of first lateral-line pore. Lateral line complete, lateral-line pores large; predorsal 6‒8; prepectoral 5‒8; preanal 39‒47. Vertebrae: predorsal 7‒10, preanal 43‒48, precaudal 52‒60, total 181‒189.

Teeth large and pointed, generally smaller than those of B. vicinus . Intermaxillary teeth in two transverse rows, each with 4‒6 fang-like teeth, exposed when mouth closed. Vomer with 2 large median teeth, the posterior one larger, and several smaller teeth behind. Maxillary teeth in 3 irregular rows on anterior portion, becoming 2 rows posteriorly, those on outermost row larger and scattered in arrangement. Dentary with 4 irregular rows of enlarged teeth at anterior end, those on outer 2 rows fang-like and exposed when mouth fully closed, narrowing to 2 rows posteriorly, those of outermost row larger.

Distribution. Indonesia, Japan, Philippines, Taiwan. Bathymetric range 432‒1022 m.

Coloration. In preserved adults, body uniformly brown to dark brown, vertical fins with black margins; pores on head and lateral line circled by white; oral cavity, gill chamber, peritoneum, stomach and intestine black. In ASIZP 66196 (210 mm TL), body pale with dorsal half slightly blackish; posterior third of dorsal and anal fins with broad black margin; three rows of black dots on body; oral cavity, tongue, gill chamber blackish; gill opening pale. In ASIZP 66181 (285 mm TL), body much lighter than others; oral cavity, tongue, gill chamber with scattered pigmentation; three rows of dots on body.

Remarks. ASIZP 66196 has a relatively large gill opening (9.1% HL) and the opening is relatively close to the pectoral-fin base, the distance is about half of its diameter, which is more similar to B. albus sp. nov. However, it has a relatively short trunk, only 1.4 times of head length, and is thus temporarily identified as the present species.

Figures

FIGURE 1. Demonstration of head pores of Bathyuroconger species. GO, gill opening; IO, infraorbital pores; LL, lateral-line pores; M, mandibular pores; POP, preopercular pores; SO, supraorbital pores; ST, supratemporal pore (indicated by arrow). From B. parvibranchialiS, ASIZP 63789.

FIGURE 4.. Scatter plots demonstrating the different mophormetric proportion of Bathyuroconger species in present study. A. gill opening height (%HL) versus preanal length. B. Head length (%PAL) versus preanal length.

FIGURE 8. Lateral view of head of three Bathyuroconger species. A. B. fowleri sp. nov., paratype, USNM 93372, 497 mm TL. B. B. hawaiienSiS, holotype, USNM 348215, 392 mm TL. C. B. parvibranchialiS, holotype, USNM 92346, 645 mm TL.

FIGURE 9. A. holotype of Bathyuroconger parvibranchialiS (Fowler, 1934), USNM 92346, 645 mm TL; compared with holotype of B. fowleri, USNM 93376 (B). C. fresh condition of B. parvibranchialiS, ASIZP 63789, nontype, 640 mm TL.