Bathycongrus guttulatus ( Günther, 1887 )

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 : 137-138

Bathycongrus guttulatus ( Günther, 1887)

Lined conger

Figs. 3D , 6C , 8A–C ; Tables 1–3, 7–8

Congromuraena guttulata Günther, 1887:252 (Type locality: off Matuku , Fiji Islands Koro Sea, South Pacific, depth 315 fathoms).

Bathycongrus guttulatus ( Günther, 1887) : Smith, 1999:1686. Castle & Smith, 1999:993. Karmovskaya & Smith, 2008:35. Karmovskaya, 2009:140. Karmovskaya, 2011:417. Ho et al., 2015:145

Specimens examined. NMMB-P4041 (1, 368), Dong-gang , 21 Mar. 1979 . NMMB-P7607 (1, 231), Kaohsiung, 4 Jul. 2004 . NMMB-P21737 (1, 310), Dong-gang , 21 Mar. 1979 . USNM 396132 (1, 570+), Taiwan , no further data . USNM 401083 (3, 295–470), Dong-gang , 25 May 2010 .

Diagnosis. A moderately large, elongate species of Bathycongrus with tail slender, filiform; 1 or 2 enlarged teeth on vomer surrounded by several smaller teeth; trunk relatively long, its length 1.6–1.9 times head length; preanal vertebrae 38–40; precaudal vertebrae 45–49; total vertebrae 156–162; and preanal lateral-line pores 36–39.

Description. Proportional measurements and meristics are provided in Tables 7–8. Body elongate, rounded in cross section anteriorly, becoming more compressed behind anus; head moderately slender, its depth and width slightly less than that of trunk; trunk relatively long, its length 1.6–1.9 times head length; tip of tail tapering and filiform; anus slightly behind anterior third of total length when tail is complete.

Dorsal fin begins over middle 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 size as eye diameter, its upper end nearly opposite middle of pectoral-fin base. Interbranchial broader than eye and gill opening.

Head relatively small, its length 13.2–14.6% TL, deepest at about occiput, tapering anteriorlyfrom this point; dorsal profile nearly flat from occiput to internasal space; snout long and broadly pointed, its length 1.6–2.1 times eye diameter, projecting beyond lower jaw; lower jaw longer than snout; fleshy part of snout with a slight 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 slightly raised rim, in front of eye slightly above mid-eye level. 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 enlarged, the canal extended to, or nearly so, caudal-fin base; 3–6 before pectoral-fin base, 6–8 before dorsal-fin origin, 36–39 [32–36 in comparative specimens] pores before anal-fin origin; total pores not available due to the preservation.

Head pores large in general ( Fig. 8C ). Supraorbital canal with 3 pores, the first (ethmoidal pore) on ventral side of tip of snout, just above lip, the second enlarged and immediately in front of anterior nostril, the third greatly enlarged and immediately above anterior nostril. Infraorbital canal with 5 pores, first 3 enlarged; the first at posterodorsal corner of anterior nostril, the second behind and below first, between anterior and posterior nostrils; the third below posterior nostril; the fourth below middle of eye; the fifth small and behind rictus; no pores behind eye. Preoperculomandibular canal with 10 pores (1 specimen with 11), 7 (1 specimen with 8) in mandibular section and 3 in preopercular; first mandibular pore very small, near anterior tip of lower jaw, third greatly enlarged, and seventh behind rictus; no pores behind eye. Supratemporal commissure with a single small pore.

Predorsal vertebrae 9 [9–11]; preanal vertebrae 38–40 [35–41 in comparative specimens]; precaudal vertebrae 45–49 [48–52]; total vertebrae 156–162 [158–163].

Teeth moderately large, conical. Intermaxillary teeth largest, curved, in 2 to 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 or 5 rows, narrower posteriorly, in 1 to 2 rows; outermost teeth slightly larger than innermost. Vomerine teeth forming a small triangular patch, 2 (rarely 1) enlarged central teeth surrounded by many smaller teeth.

Coloration. In preservative uniformly creamy white; vertical fins light grayish, gradually darker posteriorly, caudal fin blackish. Stomach black internally and pale externally; intestine uniformly black; peritoneum silver white with numerous pepper dots, densely arranged on dorsal of the chamber, becoming sparser ventrally. Mouth and gill chamber pale. NMMB-P7607 has 3 rows of dots on lateral sides of body and many scattered dots on ventral side of trunk, possibly the remains of larval pigment.

Distribution. Widely distributed in the Indo-West Pacific from Hawaii and Fiji to the western Indian Ocean.

Remarks. Bathycongrus guttulatus is very similar to B. wallacei , both always have 2 enlarged central teeth on vomer, but in B. guttulatus there are more small teeth around them, especially on lateral sides ( Figs. 6C vs. 6B). The following characters provided in Castle & Smith (1999) can separate these two species: total vertebrae 158–163 in B. guttulatus (vs. 169–181 in B. wallacei ); preanal lateral-line pores 33–38 (vs. 37–43); precaudal vertebrae 45–52 (vs. 52–57); and a cluster of vomerine teeth, with the central two to three somewhat larger than those of the short curved row flanking these on each side (vs. central vomerine teeth conspicuously enlarged, with just two or three smaller teeth behind).

In the present study we counted 36–39 preanal lateral-line pores; 45–49 precaudal vertebrae and 156–162 total vertebrae for B. guttulatus and 39–43, 53–57, 172–181, respectively, for B. wallacei , which agree with those in Castle & Smith (1999). The arrangements of vomerine teeth are also similar to Castle & Smith (1999). We also found B. guttulatus has a preanal length of 37.0–39.0% TL and trunk length 23.6–25.3% TL, both slightly longer than that of B. wallacei (34.0–36.6% TL and 20.7–23.0% TL, respectively). These two proportions can be used to separate these two species.

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 6. Vomerine tooth pattern and variation of four Bathycongrus species. Ventral view, anterior to upward. Open dots mean teeth lost or damaged. Not to scale. A. B. castlei. From left to right: NMMB-P29129 (240 mmTL), P16586 (328, holotype), P26855 (295+), P21740 (328+), USNM 441752(350+), P21736(278), 21741 (199). B. B. wallacei, P21026 (420+), P11902 (380), P21020 (344), P21739 (353+). C. B. guttulatus, P4041 (368), P7076 (231), P21737 (310). D. B. retrotinctus, P11912 (318+, 235, 235, 318, 351, 230), P11910 (288).

FIGURE 8. Bathycongrus guttulatus (Günther, 1887), NMMB-P7607, 233 mm TL. Arrow indicates the ST pore.