Bathycongrus trimaculatus, Karmovskaya & Smith, 2008

Karmovskaya, Emma S. & Smith, David G., 2008, Bathycongrus trimaculatus, a new congrid eel (Teleostei: Anguilliformes) from the southwestern Pacific, with a redescription of Bathycongrus bleekeri Fowler, Zootaxa 1943, pp. 26-36 : 27-30

Bathycongrus trimaculatus n. sp.

( Figs. 1–4)

Holotype: MNHN 2002-3924, 155 mm, Solomon Is., 25 September, 2001, station CP 1747, 09 o 21' S., 159 o 58' E, depth 364–402 m, beam trawl; C. R. V. “Alis”, Salomon 1.

Paratypes: MNHN 2000-0925 , male, 161 mm TL, Fiji, Lakeba ; 7 March, 1999, station CP 1468, 18 o 16' S., 178 o 41' W, depth 478–500 m, beam trawl; C . R. V. “Alis”, Bordau 1 ; MNHN 1995-0398 (2, 112 and 119 mm) , New Caledonia, South Loyalty Basin , 3 October, 1985, station CP 241, 22 o 09' S., 167 o 12' E, depth 470–480 m, beam trawl; C . R. V. “ Vauban ”, MUSORSTOM 4 ; MNHN 1995-0415 (3, 118– 143 mm) , New Caledonia, South Loyalty Basin , 4 October, 1985, station CC 247 , 22 o 09' S., 167 o 13' E, depth 435–460 m, shrimp trawl; C. R. V. “ Vauban ”, MUSORSTOM 4 ; MNHN 2000-1105 (1, 131 mm) , New Caledonia, South Loyalty Basin , 2 October, 1985, station CP 236, 22 o 11' S., 167 o 15' E, depth 495–550 m, beam trawl; C . R. V. “ Vauban ”, MUSORSTOM 4 ; MNHN 2002-3735 (4, 112– 153 mm) , same data as MNHN 2000-0925 ; MNHN 2007-0237 (2, 116 and 140 mm) , same data as holotype ; MNHN 2005-2589 (2, 65 and 95 mm) , Solomon Is., 1 October, 2001, station CP 1800, 09 o 21' S., 160 o 23' E, depth 357–359 m, beam trawl; C. R. V. “Alis”, Salomon 1 .

Diagnosis. A small, moderately elongate congrid eel of the subfamily Congrinae , genus Bathycongrus , with color pattern of two large black spots on anterior half of dorsal fin and one large spot on anal fin roughly opposite posterior spot on dorsal fin ( Fig. 1). Tail slender, attenuate, though not filiform. Dorsal-fin origin over tip of pectoral fin. Snout projecting beyond lower jaw. Upper labial flange rudimentary or absent. Teeth small, conical, in ca. four rows on jaws, in a short oval patch on vomer, intermaxillary teeth exposed when mouth closed. Total vertebrae 117–119, preanal lateral-line pores 26–29.

Description (values given for holotype, with those of paratypes in parentheses). Measurements as % TL: preanal length 35.5 (32.8–36.6), predorsal length 18.7 (17.2–19.6), head length 15.8 (14.7–16.4), trunk 19.6 (17.2–20.9), depth at gill opening 5.5 (5.2–6.8), depth at anus 4.5 (4.2–5.6); as % of head length: snout length 26.1 (21.5–25.4), horizontal eye diameter 22.9 (19.4–23.8), snout to rictus 35.5 (31.6–35.7), gill opening 14.3 (13.5–15.9), interbranchial 18.4 (18.4–21.4), pectoral-fin length 34.7 (31.1–37.5). Meristic characters: preanal lateral-line (LL) pores 27 (26–29), preoperculomandibular (POM) pores 10, infraorbital (IO) pores 5, supraorbital (SO) pores 3, supratemporal commissure (STC) pores 1 (0–1). Predorsal vertebrae 9 (7–9), preanal 29 (28–30), precaudal 38 (37–39), total 117 (117–119). Pectoral-fin rays 12 (11, 13), dorsal fin-rays 219 (203– 221), preanal dorsal fin-rays 45 (39–48), anal fin-rays 164 (164–177), caudal fin-rays 5+3+2. Branchiostegal rays 9 (8, 9, 9).

Body moderately elongate, round in cross section anteriorly, becoming more compressed posteriorly, tip of tail moderately attenuate; anus near anterior third of total length. Dorsal fin begins over posterior part of appressed pectoral fin ( Fig.2, 3), continuous around tip of tail with caudal and anal fins. Anal fin begins immediately behind anus. Pectoral fin well developed. Gill opening relatively large, upper end nearly opposite middle of pectoral-fin base; interbranchial broader than gill opening. Myorhabdoi absent, fin rays segmented (from radiograph).

Head deepest about midway between gill opening and tip of snout, tapering anteriorly from this point; snout equal or slightly greater than eye diameter, projecting well beyond lower jaw; fleshy part of snout with a slight median keel on underside, projecting anteriorly beyond anterior end of intermaxillary tooth patch; rictus nearly below middle of eye. Lower jaw with a downturned flange, upper jaw with flange greatly reduced or absent. Eye relatively large. Anterior nostril tubular, near tip of snout, directed ventrolaterally. Posterior nostril elliptical, with a slightly raised rim, at mid-eye level.

Lateral line complete, 26–29 pores before anus. Head pores large ( Fig. 3). Supraorbital canal with three 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. Infraorbital canal with five pores, four slit-like pores along upper jaw flange, the first three noticeably enlarged, and one large, round pore behind rictus at mid-eye level; adnasal pore absent; no pores behind eye. Preoperculomandibular canal with 10 pores, six before and four behind rictus. Supratemporal commissure variable, 10 specimens with no pores, three specimens with a single, tiny medial pore.

Teeth ( Fig. 4) moderately large, conical. Intermaxillary in two transverse rows, separated from maxillary and vomerine teeth, mostly excluded from closed mouth. Maxillary and mandibular teeth in bands, wider anteriorly, roughly in four to five rows, narrower posteriorly, in one to two rows; outermost teeth larger than innermost. Vomerine tooth patch longer than broad, reaches to level of posterior nostril; teeth conical, shorter than those of intermaxillary, about equal size, in three to four rows anteriorly and one to two rows posteriorly.

Gas bladder terminates far behind anus. Stomach reaches about one-half of distance to anus.

Color in preservative light, yellowish-brown; lateral and ventral surfaces of body and tail without chromatophores; dorsal surface with a darker wash composed of numerous tiny brown chromatophores on either side of dorsal fin. A dark streak on top of snout; dark pigment outlining supratemporal canal; an indistinct patch of pigment on opercle in front of pectoral-fin base (specimens from New Caledonia and Fiji lighter than those from Solomons – they lack the dark pigment outlining supratemporal canal and the indistinct patch of pigment on opercle). Pectoral fins pale. Dorsal and anal fins largely unpigmented except for three distinct black blotches, covering distal edges of several rays; dorsal fin with two blotches, the anterior located immediately behind pectoral-fin tip, the posterior behind anus, opposite or slightly before anal spot; anal fin with one blotch behind anus at a distance slightly more than snout length. Stomach and intestine black in larger specimens, blackish only anteriorly in smaller specimens. Branchial cavity pale.

The specimens range from 65 to 161 mm. The largest specimen is a mature male, 161 mm TL, with a regenerated tail and an incomplete number (111+) of vertebrae.

Etymology. From the Latin words tria (three) and macula (spot) in reference to the number of spots on the dorsal and anal fins.

Distribution. Known from six localities, three from New Caledonia, one from Fiji and two from the Solomon Islands at 357–550 m depth.

Comparisons. The new species is clearly a member of the subfamily Congrinae , based on the following characters: preanal length less than 40% TL, posterior nostril at or above mid-eye level, tip of tail soft and pliable, dorsal- and anal-fin rays segmented. We place it in Bathycongrus based on the following characters: snout projecting beyond lower jaw; teeth conical, in narrow bands on jaws, none long and fanglike; vomerine tooth patch not greatly elongate; pores along upper lip enlarged; no flange on upper lip; tip of tail slender, attenuate, but not filiform; stomach and intestine black ( Smith, 1989a: 522; Smith, 1999: 1682). Nevertheless, it differs in some respects from the other Indo-Pacific species of Bathycongrus . In all except B. bleekeri , the vomerine tooth patch consists of one or two distinctly enlarged median teeth, flanked on either side by a curved row of smaller teeth ( Castle & Smith, 1999: 979, figs. 3–4). In B. trimaculatus , the vomerine teeth are arranged in a slightly elongate patch, none greatly enlarged, and all more or less the same size. Bathycongrus bleekeri also has a somewhat elongate vomerine tooth patch, with none of the teeth significantly enlarged, but B. bleekeri lacks the spots on the dorsal and anal fins, and it has fewer vertebrae (113). Among extralimital species, Bathycongrus dubius from the Atlantic also has the vomerine teeth in an elongate patch with none of them greatly enlarged. That species, however, has more vertebrae (120–145), reaches a larger size (at least 443 mm), and lacks the three spots on the fins.

Bathycongrus trimaculatus is a small species, reaching maturity at a minimum size of approximately 160 mm TL, and it has fewer vertebrae (117–119) than any of the other species except B. bleekeri . Many congrid eels have dark-edged dorsal and anal fins, but B. trimaculatus is the only one that has this pigment confined to three discrete, conspicuous spots.