Bathycongrus albimarginatus Huang, Smith, Chang & Chen, 2018

Huang, Jian-Fu, Ho, Hsuan-Ching, Chang, Yung-Hsu, Smith, David G. & Chen, Hong-Ming, 2018, Two new species of the conger eel genus Bathycongrus (Anguilliformes: Congridae) from Taiwan, Zootaxa 4454 (1), pp. 107-117 : 108-113

Bathycongrus albimarginatus Huang, Smith, Chang & Chen , sp. nov.

White-margin deep-sea conger

Figs. 1–2 ; Tables 1–2

Holotype. TOU-AE 7280 (560 mm TL), 23°14'N, 121°25'E, off Wushibi , Changbin township, Taitung county, Taiwan, 250–300 m, 4 Jan. 2017, coll. J.- S. Chiu.

Paratypes. 15 specimens, 362–651+ mm TL. TOU-AE 5548 (573 mm TL), TOU-AE 5549 (524 mm TL), TOU-AE 5550 (396 mm TL), TOU-AE 5561 (362 mm TL), 23°14'N, 121°25'E, off Wushibi , Changbin township, Taitung county, Taiwan, 20 May 2010, coll . J.- S. Chiu. TOU-AE 6678 (651+ mm TL), 23°29'N, 121°30'E, off Shihtiping , Fengbin township, Hualien county, Taiwan, 2 Nov. 2012, coll . J.- S. Chiu. TOU-AE 7233 (511 mm TL), TOU-AE 7234 (427 mm TL), 23°14'N, 121°25'E, off Wushibi , Changbin township, Taitung county, Taiwan, 8 May. 2014, coll . J.- S. Chiu. TOU-AE 7276 (491 mm TL), NMMB-P25749 (formerly TOU-AE 7275) (537 mm TL), 23°29'N, 121°30'E, off Fengbin township , Hualien county, Taiwan, 250–300 m, 18 Dec. 2016 . TOU-AE 7277 (558+ mm TL), NMMB-P25750 (formerly TOU-AE 7278) (490 mm TL), 23°14'N, 121°25'E, off Changbin township , Taitung county, Taiwan, 250–300 m, 15 Jan. 2017 . TOU-AE 7268 (580+ mm TL), 18 Dec. 2014. TOU- AE 7269 (531 mm TL), 9 Jan. 2015. All specimens collected by J.- S. Chiu. USNM 437349 (515+ mm TL), Changbin , 15 Sep. 2011 . USNM 441813 (490+ mm TL), Chang-bin , 7 Nov. 2011 .

Diagnosis. A moderately large, robust species of Bathycongrus with 2 enlarged teeth surrounded by small teeth on the vomer; body dark grayish with broad bright white margins on dorsal and anal fins; 5 pores on supratemporal canal; preanal vertebrae 50–52, precaudal vertebrae 68–70, total vertebrae 196–201; and preanal lateral-line pores 47–53.

Description. The following values are given for the holotype, followed by the range of all types in parentheses.

Body rather stout, rounded in cross section anteriorly, becoming more compressed behind anus and in posterior portion; head strong and stout, its depth and width slightly smaller than those of trunk; trunk moderately long, its length 2.3 (2.0–2.5) times head length; tip of tail tapering and filiform; anus near anterior two-fifths of total length (when tail complete).

Dorsal fin begins over posterior half of pectoral fin, continuous around tip of tail with caudal and anal fins. Anal fin begins immediately behind anus. Pectoral fin well developed, roundly pointed distally with a narrow base. Gill opening large, about same as eye diameter or slightly smaller, its upper end nearly opposite middle of pectoralfin base. Interbranchial width much greater than twice width of gill opening.

Head relatively small, its length 12.1% (10.9–13.1%) TL, 30.4% (27.9–33.5%) PAL, deepest at about occiput, slightly tapering anteriorly from this point; dorsal profile nearly flat from occiput to internasal space; snout stout and broadly rounded, its length greater than eye diameter, projecting beyond lower jaw; lower jaw longer than snout; fleshy part of snout with a weak median keel on underside, projecting anteriorly beyond anterior end of intermaxillary tooth patch; rictus below posterior half of eye.

Anterior nostril tubular, near tip of snout, directed ventrolaterally. Posterior nostril elliptical, with a clear raised rim, in front of upper margin of eye. Upper lip with flange greatly reduced; lower lip with a well-developed downturned flange. Tongue free, long, and broad.

Lateral line complete, first pore on each side slightly reduced, the canal extended to caudal-fin base; 13 (11–13) before dorsal-fin origin, 6 (5–6) before pectoral-fin base, 51 (48–53) pores before anal-fin origin; total pores 134+ (160–174).

Head pores vary in size, mostly small but some enlarged ( Figs. 2A, B ). Supraorbital canal with at least 9 pores, the first (ethmoidal) on ventral side of tip of snout, just ahead of lip; the second enlarged and immediately in front of anterior nostril; the third greatly enlarged and immediately above anterior nostril; a small fourth pore on dorsal surface of snout between both nostrils, some paratypes have none while others have 1–4 small pores at same region, but not arranged symmetrically; frontal region with 2 pores. Infraorbital canal with four regular pores along the upper jaw; the first pore at posterodorsal corner of anterior nostril; the second enlarged, between both nostrils; the third greatly enlarged, beneath eye at vertical between posterior nostril and anterior margin of eye; the fourth small, below middle of eye; the fifth small and behind rictus and below posterior margin of eye; 4 principal pores behind eye, with some additional small pores behind the eye, some forming small clusters. Preoperculomandibular canal with 11 pores, six before and five behind rictus, posteriormost 3 pores (e.g. preopercular) enlarged (TOU- AE6678 has 8 additional small pores on right side and 2 on left side above the POP pores; TOU-AE7276 has 1 additional mandibular pore on both sides). Supratemporal with 5 pores, the lowermost pore slightly below level of first lateral-line pore.

Predorsal vertebrae 14 (14); preanal vertebrae 52(50–52); precaudal vertebrae 69 (68–70); total vertebrae 197 (196–201).

Teeth various in size, conical and all sharp distally ( Fig. 2C ). Intermaxillary in about two transverse rows, clearly separated from maxillary and vomerine teeth by a large space, barely excluded from closed mouth. Maxillary and mandibular teeth in bands, wider anteriorly, roughly in four to five rows anteriorly, gradually narrower posteriorly, in one or two rows; outermost teeth slightly larger than innermost. Vomerine tooth patch longer than width, reaches to nearly level of posterior nostril, teeth conical, in approximately four rows anteriorly, narrower posteriorly, the middle teeth larger than outer ones and slightly smaller than those of intermaxillary.

Measurements for holotype (in mm): total length 560; head length 68.0; predorsal length 91.0; preanal length 224.0; trunk length 156.0; tail length 336.0; depth at gill opening 28.8; depth at mid-anus 34.4; eye diameter 8.9; interorbital width 15.0; snout length 18.1; interbranchial width 20.2; body width 30.2; postorbital length 42.4; pectoral fin length 23.8; gill opening length 10.5; upper jaw length 28.6; lower jaw length 26.1.

Coloration. Body when fresh ( Fig. 1 ) generally dark grayish, ventral surface of anterior two-thirds of body paler; pectoral fins pale white. Vertical fins light grayish anteriorly, gradually turning to dark grayish posteriorly, with prominent broad white margins. Caudal fin dark grayish. Lateral-line pores with white margin. Mouth cavity and gill chamber pale. Peritoneum pale with numerous tiny grayish dots; outer surface of stomach pale; intestine black.

Size. The largest specimen examined is a mature male with 651+ mm TL (the tail tip is broken).

Etymology. From the Latin words albus (white) and margin (margin) in reference to the borderline color on the dorsal, caudal and anal fins.

Distribution. Known from the type series collected from eastern Taiwan off three localities, Changbin, Shihtiping and Wushibi by hook and line at about 250– 300 m.

Remarks. Bathycongrus albimarginatus sp. nov. belongs with the congeners with 2 enlarged teeth surrounded by small teeth on the vomer, which comprise 8 species previously, and can be distinguished by having more total vertebrae (196–201). Table 2 shows 6 meristic characters to differentiate these species ( Castle & Smith, 1999; Karmovskaya, 2009; Smith & Ho, 2018).

Of them, B. albimarginatus is most similar to Bathycongrus parapolyporus Karmovskaya, 2009 in having 11 preopercular-mandibular pores and 8 infraorbital pores. It can be further distinguished from B. parapolyporus in having the rictus extend to nearly below posterior margin of eye (vs. to mid-eye level); 196–201 total vertebrae (vs. 158–160); 11–13 pores before dorsal-fin origin (vs. 9–10); 5 supratemporal pores (vs. 1); additional small pores on head (vs. none); and clear white margin on vertical fins (vs. no clear white margin). The character of vertical fins with distinct white margin in B. albimarginatus rarely appears on the other Bathycongrus species.

The outermost supratemporal pore is located at the junction of the temporal, preopercular, and lateral-line canals. We assign it to the supratemporal canal because it resembles the supratemporal pores in size (smaller than lateral-line pores) and is located at the junction of the canals, whereas the true first lateral-line pore is distinctly behind that point.

There seems to be considerable variation in the number of head pores. In some specimens there are differences between one side and the other in some canals.

Figures

FIGURE 1. Bathycongrus albimarginatus sp. nov., A-C, holotype, 560 mm TL, TOU-AE7280. A, B. fresh color after frozen, C. preserved.

FIGURE 2. Bathycongrus albimarginatus sp. nov., from the holotype, 560 mm TL, TOU-AE7280. A. lateral view of head showing the head pores. B. Dorsal view of head. C. ventral view of upper mouth showing the jaw teeth.