Bathycongrus brunneus Huang, Ho & 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 : 113-116

Bathycongrus brunneus Huang, Ho & Chen , sp. nov.

Brown deep-sea conger

Figs. 3–4 ; Tables 1–2

Holotype. TOU-AE 7261 (540+ mm), mature female, Changbin , Taitung, eastern Taiwan, hook and line, bottom, 15 Dec. 2014, coll. J. - S. Chiu.

Diagnosis. A moderately slender species of Bathycongrus with tail presumably tapering, filiform; body uniformly brownish, and dorsal and anal fins black to gray with narrow white margin; vomerine teeth forming a long triangular patch, with 13 subequal teeth at front and sides; preanal vertebrae 44, precaudal vertebrae 59, total vertebrae 174+; and preanal lateral-line pores 44.

Description. Body rather stout, rounded in cross section anteriorly, becoming more compressed behind anus and posterior portion; head moderately slender, its depth and width about same as these of trunk; trunk moderately long, its length 1.5 times head length; tip of tail tapering and presumably filiform (tip of tail slightly damaged and healed); anus near anterior third of total length.

Dorsal fin begins over anterior half of pectoral fin, continuous around tip of tail with caudal and anal fins. Anal fin begins immediately behind anus. Pectoral fin well developed, pointed distally with a narrow base. Gill opening relatively large, about same as eye diameter, its upper end nearly opposite middle of pectoral-fin base. Interbranchial broader than gill opening and eye.

Head relatively large, its length 40.5% PAL (ca. 14.6% TL), deepest at about occiput, slightly tapering anteriorly from this point; dorsal profile nearly flat from occiput to internasal space; snout long and broadly pointed, its length 1.5 times eye diameter, projecting beyond lower jaw; lower jaw longer than snout; fleshy part of snout with a high median keel on underside, projecting anteriorly beyond anterior end of intermaxillary tooth patch; rictus below middle of eye.

Anterior nostril tubular, near tip of snout, directed ventrolaterally. Posterior nostril elliptical, with a clear raised rim, in front of eye nearly at upper eye level. Upper lip with flange strongly reduced; lower lip with a welldeveloped downturned flange. Tongue free, long, and broad.

Lateral line complete, first pore on each side slightly enlarged, the canal extended to caudal-fin base; 10 pores before dorsal-fin origin, 6 pores before pectoral-fin base, 44 pores before anal-fin origin; total pores 117+.

Head pores vary in size ( Fig. 4A ), mostly enlarged. Supraorbital canal with 3 pores; the first (ethmoidal pore) on ventral side of snout tip, just ahead of lip; the second enlarged, about twice the size of first, and immediately in front of anterior nostril; the third greatly enlarged and immediately above anterior nostril, about same size of anterior nostril; no pore at frontal region. Infraorbital canal with 5 pores, first 3 enlarged; the first at posterodorsal corner of anterior nostril; the second to fourth along lip; the second and third between anterior and posterior nostrils; the fourth below anterior margin of eye; and the fifth small and behind rictus; no pores behind eye. Preoperculomandibular canal with 10 pores; mandibular pores 7 along lower jaw and 3 behind rictus; the first pore small, near anterior tip of lower jaw, the third greatly enlarged; 3 pores in preopercular section. Supratemporal commissure with a single small median pore.

Predorsal vertebrae 13; preanal vertebrae 44; precaudal vertebrae 59; total vertebrae 174+ (tip of tail damaged, but probably only few vertebrae lost).

Teeth large, conical and sharp ( Fig. 4B ). Intermaxillary teeth largest, curved, in about 4 transverse rows, separated from maxillary and vomerine teeth, mostly excluded from closed mouth. Maxillary and mandibular teeth in bands, wider anteriorly, roughly in 4 rows, narrower posteriorly, in 1 or 2 rows; outermost teeth greatly enlarged, innermost teeth smallest. Vomerine teeth forming a long triangular patch, with 13 subequal teeth; some are somewhat enlarged, but not much larger than the rest as in those congeners with two enlarged teeth on the vomer.

Measurements of holotype in mm. Total length 540+, head length 79.0, preanal length 195, predorsal length 87.6, trunk length 116, tail length 345+, depth at gill opening 28.8, depth at anus 34.0, width at anus 22, snout length 20.3, eye diameter 13.6, rictus 32.5, lower jaw 29.0, gill opening width 14.4, interbranchial width 19.0, pectoral-fin length 24.2.

Coloration. When preserved ( Fig. 3C ), body, tail and head uniformly grayish brown, except for irregular unpigmented areas on lateral sides of snout, lips and underside of head. Pectoral fin pigmented internally and basally. Mouth cavity and gill chamber pale, except for some small scattered patches of black pigments on roof of mouth and wall of gill chamber. Dorsal and anal fins pigmented internally with white membranes in anterior portions, gradually becoming a narrow white base and broadly blackish with narrow white margins, then entirely black to the caudal fin. Stomach and intestine uniformly black; peritoneum densely covered by black pepper dots making the membrane brownish.

Etymology. From Latin brunneus , brown.

Remarks. Bathycongrus brunneus sp. nov. may belong to the high-vertebral-count group. However, the teeth on the vomer are not especially enlarged as in the congeners. Of these species, it is most similar to B. wallacei and Bathycongrus longicavis Karmovskaya, 2009 . It can be separated from B. wallacei by having 13 subequal teeth on the vomer (vs. 2 enlarged teeth followed by 2 or 3 smaller ones behind); relatively more preanal vertebrae (44 vs. 38–43, mainly 40–42); relatively more precaudal vertebrae (59 vs. 53–57); a relatively short trunk (59.5% vs. 59.7–63.6% PAL). It differs from B. longicavis in having 13 subequal teeth on the vomer (vs. 2 enlarged teeth followed by 3 small ones behind); a shorter trunk (59.5% vs. 65.4% PAL); a larger head (40.5% vs. 34.3% PAL); a shorter snout (25.7% vs. 30.9% HL); a larger eye (17.2% vs. 15.9% HL); more predorsal vertebrae (13 vs. 9); fewer preanal vertebrae (44 vs. 47); and fewer precaudal vertebrae 59 (vs. 67).

The other species with similar vertebral count is Bathycongrus odontostomus ( Fowler, 1934) (total vertebrae 164–177) which has a black mouth and branchial cavities and can be easily separated from the new species.

Figures

FIGURE 3. Bathycongrus brunneus sp. nov., A–B, holotype, 540+ mm TL, TOU-AE7261. A. fresh color after frozen, B. preserved.

FIGURE 4. Bathycongrus brunneus sp. nov., from the holotype, 540+ mm TL, TOU-AE7261. A. lateral view of head showing the head pores. B. ventral view of upper mouth showing the jaw teeth.