Bathycongrus macroporis ( Kotthaus, 1968 )

Smith, David G. & Ho, Hsuan-Ching, 2018, The congrid eel genus Bathycongrus of Taiwan, with descriptions of three new species (Anguilliformes: Congridae), Zootaxa 4454 (1), pp. 118-146 : 138-140

Bathycongrus macroporis ( Kotthaus, 1968) (New record)

Figs. 3F , 9A–C ; Tables 1–3, 7–8

Pseudophichthys macroporis Kotthaus, 1968:35 , figs. 138–140, 152 (type locality: off Sokotra Island , Indian Ocean, 11°33.9’N, 52°54’E to 11°38’N, 52°52’E, depth 337– 175 m).

Specimens examined. NMMB-P29128 (1, 395), 15 Sep. 2011; USNM 398471 (1, 415+), 23 Sep. 2008; from Chang Bin , Taitung, eastern Taiwan, by hook and line.

Diagnosis. A large, robust species of Bathycongrus with posterior nostril above level of upper margin of eye; band of granular teeth on jaws and vomer; vomerine teeth forming a long and broad patch; trunk 1.3–1.4 times head length; predorsal vertebrae 9–10, preanal vertebrae 34–36, precaudal vertebrae 39–40, total vertebrae 148+; and preanal lateral-line pores 30–32.

Description. Proportional measurements and meristic data are shown in Tables 7–8. Head length 2.3 (2.4 in USNM 398471) in PAL, 6.4 (*) in TL; preanal length 2.8 (*) in TL; predorsal length 2.2 (2.3) in PAL, 6.0 (*) in TL; trunk length 1.8 (1.7) in PAL, 4.8 (*) in TL; tail length 1.6 (*) in TL; depth at head 6.2 (6.7) in PAL, width at head 7.8 (7.1) in PAL. Snout length 4.0 (4.4) in HL; eye diameter 5.6 (7.0); interorbital width 7.1 (7.3); upper jaw 2.9 (3.1); gill opening width 7.2 (6.7); interbranchial width 5.1 (5.0); pectoral-fin length 2.9 (3.1).

Body moderately elongate, robust, more or less uniform in depth over head and trunk, round in cross section anteriorly, becoming compressed posteriorly; trunk stout, 1.3–1.4 times of head length; tip of tail tapering, moderately filiform; anus near anterior third of total length.

Dorsal fin begins over pectoral fin, slightly behind fin base; continuous around tip of tail with caudal and anal fins. Anal fin begins immediately behind anus. Pectoral fin well developed, long and broad. Gill opening moderately large, about same size as eye diameter, its upper end opposite middle of pectoral-fin base; interbranchial broader than gill opening and eye.

Head relatively large, its length 15.5% TL, deepest about occiput, slightly tapering anteriorly from this point; dorsal profile nearly flat from occiput to internasal space; snout broadly rounded in dorsal view, its length 1.4–1.6 eye diameter, projecting beyond lower jaw; fleshy part of snout with a slight 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 slightly raised rim, in front of eye above level of upper margin of eye and behind anterior margin of eye. Upper lip with flange greatly reduced; lower lip with well-developed downturned flange. Tongue free, long, and broad.

Lateral line complete, first pore on each side slightly enlarged, the canal extended to caudal-fin base; 5 (5) before pectoral-fin base, 6 (7) pores before dorsal-fin origin, 30 (32) before anal-fin origin, total pores not countable.

Head pores vary in size, most enlarged to some extent ( Fig. 9C ). Supraorbital canal with 3 pores; the first (ethmoidal pore) small, on ventral surface of snout tip, just above 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 as anterior nostril. Infraorbital canal with 5 pores, the first 3 pores enlarged; the first at posterodorsal corner of anterior nostril; second behind and below the first, on upper lip; third behind second, on upper lip, about midway between anterior nostril and eye; fourth slightly smaller, below anterior part of eye; fifth behind and slightly below rictus; no pores behind eye. Preoperculomandibular canal with 10 pores; 7 pores in mandibular section, 6 along lower jaw and 1 behind rictus; first pore small, near tip of lower jaw, second and third pores progressively larger, the third the largest in the series; fourth through seventh smaller; 3 pores in preopercular section. Supratemporal commissure with a single median pore.

Predorsal vertebrae 9 (10); preanal vertebrae 34 (36); precaudal vertebrae 40 (39). Total vertebrae not available due to the damaged tails in both specimens, the incomplete counts are 148+ (117+). The holotype was also incomplete, with 126 vertebrae ( Kotthaus, 1968).

Teeth on jaws moderately stout to blunt ( Fig. 3F ). Intermaxillary with 5 or 6 transverse rows of teeth, those on outer 2 rows large, gradually smaller posteriorly, not exposed when mouth closed. No clear gap between intermaxillary and vomerine teeth. Vomerine teeth conical, forming a long patch, extending about half length of maxillary tooth band. Maxillary teeth in about 5 irregular rows, gradually narrowing to 1 or 2 rows posteriorly, outer teeth longest, inner teeth gradually smaller. Mandibular teeth similar in size and arrangement to those on maxilla.

Coloration. Light brown dorsally, paler ventrally. Dorsal and anal fin pale with broad black margin; posterior portion entirely black. Pectoral fin pale. Stomach, intestine, and peritoneum pale. Mouth cavity pale; gill chamber unpigmented on outer side, inner side with small, closely spaced melanophores forming a slight darkening.

Distribution. Known from off Sokotra Is. in the western Indian Ocean and now Taiwan.

Remarks. This species is placed in Bathycongrus provisionally. The lack of any notably enlarged teeth, and the long and broad vomerine tooth patch differ from the condition found in most species of Bathycongrus , which have a short patch with at least a few teeth enlarged. The elevated position of the posterior nostril, above the dorsal margin and behind the anterior margin of the eye, differs markedly from the other species, which have the nostril in front of the eye near mid-eye level. Kotthaus (1968) placed it in the genus Pseudophichthys , but the type species of that genus, P. splendens (Lea, 1913) , is more slender and has the posterior nostril in front of mid-eye. This species was known previously only from the holotype collected in the northwestern Indian Ocean. Its discovery in Taiwan suggests that it may be present in intermediate areas as well.

Figures

FIGURE 3. Tooth pattern on upper jaw. A. Bathycongrus bimaculatus sp. nov., NMMB-P7012, paratype. B. B. bleekeri, NMMB-P26214. C. B. castlei sp. nov., NMMB-P21740, paratype. D. B. guttulatus, NMMB-P7607. E. B. graciliceps sp. nov., holotype. F. B. macroporis, NMMB-P29128. Not to scale.

FIGURE 9. Bathycongrus macroporis (Kotthaus, 1968), USNM 398471, 415+ mm TL. Bar indicates locality of posterior nostril. Arrow indicates the ST pore.