Bathycongrus wallacei ( Castle, 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 : 142-145

Bathycongrus wallacei ( Castle, 1968)

Longnose conger

Figs. 6B , 11 ; Tables 1–3, 7–8

Congrina wallacei Castle, 1968:709 , pl. 107B, figs. 1a–b (Type locality: off the mouth of Limpopo River, Mozambique, depth 480–500 meters).

Bathycongrus wallacei ( Castle, 1968) : Castle & Smith, 1999:993. Karmovskaya & Smith, 2008:35. Karmovskaya, 2009:145, Karmovskaya, 2011:417. Ho et al., 2015:145.

Specimens examined. ASIZP 53853 (1, 289), Dong-gang, Ping-tung, 23 May. 1966. ASIZP 57963 (1, 422), Da-xi, Yi-lan, 8 Feb. 1990. ASIZP 71583 (1), Da-xi , 15 Oct. 1997 . ASIZP 71584 (1), Da-xi , 24 Apr. 2004 . ASIZP 66772 (1, 165), Daxi , 8 Aug. 2005 . NMMB-P1469 (1), Dong-gang , 13 Feb. 1962 . NMMB-P1362 (1), NMMB-P1470 (1), Dong-gang , 6 Feb. 1966 . NMMB-P1471 (1), Dong-gang , 1 Aug. 1965 . NMMB-P3680 (2, 453+, 469), Dong-gang , 28 May. 2002 . NMMB-P3820 (1, 326), Fong-gang , 23 Aug. 2001 . NMMB-P6214 (1), Da-xi , 8 May. 2003 . NMMB-P7962 (1), Dong-gang , 11 Jun. 2004 . NMMB-P8047 (1), Fang-shan , Pingtung, 17 Jun. 2004 . NMMB- P9186 (1, 324). Da-xi, 8 Sep. 2008. NMMB-P9236 (2), NMMB-P9243 (2, 364–450), Dong-gang , 18 Sep. 2008 . NMMB-P9336 (3), NMMB-P9438 (3), Dong-gang , 27 Aug. 2008 . NMMB-P11899 (1, 325), Dong-gang , 15 Feb. 2011 . NMMB-P11902 (1, 377), no data. NMMB-P12664 (3), Dong-gang , 16 Apr. 2004 . NMMB-P13871 (3, 323+–437), Dong-gang , 10 Aug. 2011 . NMMB-P14018 (1), Dong-gang , 6 Sep. 2011 . NMMB-P16290 (5), NMMB-P16314 (4), Nan-fan-ao, 20 Jul. 2010. NMMB-P16369 (1, 196), Dong-gang , 21 Feb. 2012 . NMMB- P17762 (1, 443), Dong-gang , 8 Aug. 2012 . NMMB-P17888 (1, 414), Dong-gang , 25 Jan. 2013 . NMMB-P20661 (1, 455), NMMB-P20676 (1, 397), Chang-bin , Taitung, 10 May. 2012 . NMMB-P20678 (1, 369), Chang-bin , 23 Jul. 2012 . NMMB-P20996 (1, 457+), Dong-gang , 12 Mar. 2014 . NMMB-P20679 (2), Chang-bin , 28 Apr. 2012 . NMMB-P21010 (1, 342), NMMB-P21026 (1, 420+), NMMB-P21033 (1, 370), NMMB-P21034 (1, 335), Donggang , 12 Mar. 2014 . NMMB-P21739 (1, 355+), Dong-gang , 15 Feb. 2011 . NMMB-P21707 (1), Dong-gang . NMMB-P21735 (2), Dong-gang , 10 Aug. 2011 . NMMB-P21798 (1, 243), Dong-gang , 7 Nov. 2013 . NMMB- P22454 (1, 295), Dong-gang, 11 Feb. 2015. NMMB-P24509 (1, 320), NMMB-P24516 (1, 322), Dong-gang , 24 Aug. 2016 . NMMB-P24920 (1), Dong-gang . NMMB-P26029 (1, 325, cleared & stained), Dong-gang , 15 Apr. 2017 . NMMB-P26385 (1, 180), Da-xi , 1 Jul. 2017 . NMMB-P26394 (9, 267–385), Nan-fan-ao, 1 Jul. 2017. NMMB-P26553 (24, 255–511), Dong-gang , 3 Mar. 2017 . NMMB-P26755 (1, 374), Da-xi , 24 Dec. 2015 . NMMB- P27606 (5, 171–291), Dong-gang , 3 Mar. 2017 . NMMB-P28487 (1, 271), Dong-gang , 30 Jan. 2018. NMMB- P27885 (1, 340) , NMMB-P27886 (1, 373), NMMB-P27887 (1, 374), Dong-gang , 3 Mar. 2017 . NMMB-P28212 (1, 195), Dong-gang , 10 Nov. 2017 . NMMB-P28258 (1, 263), NMMB-P28276 (1, 372), NMMB-P28435 (1, 354), NMMB-P28439 (1, 273), NMMB-P28440 (1, 263), Dong-gang , 15 Nov. 2017 . NMMB-P29130 (3, 322–428), Dong-gang , 27 Mar. 2018 . USNM 395266 (1, 345+), Dong-gang , 16 May 2008 . USNM 398443 (1, 366+), Taiwan , 2009 . USNM 398513 (1, 354+), USNM 398514 (1, 370), USNM 398515 (1, 248), Da-xi , 6 Nov 2009 . USNM 398558 (1, 315), USNM 398559 (1, 328), USNM 398560 (1, 362), USNM 398729 (1, 234), USNM 398730 (1, 292), USNM 398731 (1, 332), Dong-gang , 10 Nov. 2009 . USNM 398793 (1, 280+), USNM 398794 (1, 290), USNM 398795 (1, 280), Nan-fang Ao , 18 Nov. 2009 . USNM 399861 (1, 352), USNM 400321 (1, 402), Donggang , 8 Nov. 2009 . USNM 401054 (1, 184), USNM 401055 (1, 362+), Da-xi , 6 Nov. 2009 . USNM 401084 (1, 403), Dong-gang , 25 May 2010 . USNM 404432 (1, 386), Taiwan , 2009 . USNM 437335 (1, 345+), Dong-gang , 28 Sep. 2013 . USNM 437336 (1, 417), Dong-gang , 13 Mar. 2015 . USNM 437337 (470+), Da-xi , 11 Oct. 2015 . USNM 437338 (1, 435+), Da-xi , 15 Oct. 2015 . USNM 439062 (1, 570), USNM 439063 (1, 386), USNM 439064 (1, 395), Dong-gang , 4 Feb. 2016. Twenty-five uncatalogued specimens (231+–523+).

Diagnosis. A moderately large, slender species of Bathycongrus with tail tapering and filiform; two enlarged teeth on vomer followed posteriorly by 2 smaller teeth side by side; trunk length 1.5–1.7 times head length; preanal vertebrae 38–43 (mainly 40–42); precaudal vertebrae 53–57, total vertebrae 172–181; and preanal lateral-line pores 39–43.

Description. Proportional measurements and meristics are provided in Tables 7–8. Body elongate, round in cross section anteriorly, becoming more compressed behind anus and posterior portion; head moderately slender, its depth and width slightly less than these of trunk; trunk moderately long, its length 1.5–1.7 times of head length; tip of tail tapering and filiform; anus slightly behind anterior third of total length when tail is complete.

Dorsal fin begins over origin to 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 with a narrow base. Gill opening large, about same size as eye, its upper end opposite middle to lower part of pectoral-fin base; interbranchial broader than gill opening and eye.

Head small, deepest about occiput, tapering anteriorly from this point; dorsal profile nearly flat from occiput to internasal space; snout long, blunt anteriorly in dorsal view, its length 1.7–2.0 times eye diameter, projecting beyond lower jaw; lower jaw longer than snout; fleshy part of snout with a median keel on underside, projecting anteriorly beyond anterior end of intermaxillary tooth patch; rictus below posterior margin of eye.

Anterior nostril tubular, near tip of snout, directed ventrolaterally. Posterior nostril elliptical, with a slightly raised rim, in front of eye above mid-eye level. Upper lip with a shallow, free flange; lower lip with a welldeveloped downturned flange. Tongue free, long, and broad.

Lateral line complete, first pore on each side slightly enlarged, the canal extends to, or nearly to, caudal-fin base; 5–7 before pectoral-fin base, 6–9 pores before dorsal-fin origin (usually 1 or 2 more than prepectoral); 39–43 before anal-fin origin [38–40 in comparative specimens]; total pores not countable.

Head pores vary in size, mostly enlarged. Supraorbital pores 3; the first (ethmoidal pore) on ventral side 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, first 3 pores enlarged, second to fourth above the flange; first pore at posterodorsal corner of anterior nostril; second pore behind and slightly below the first, between anterior and posterior nostrils; the third between posterior nostril and anterior margin of eye; the fourth below middle of eye; the fifth small and behind rictus; no pores behind eye. Preoperculomandibular canal with 10 pores, 7 in mandibular section and 3 in preopercular; the first mandibular pore very small, near anterior tip of lower jaw, the third greatly enlarged, the seventh behind rictus. Supratemporal commissure with 1 pore (cf. Fig. 1 ).

Predorsal vertebrae 8–11 (mainly 8 or 9; 9–12 in comparative specimens); preanal vertebrae 38–43 (mainly 40–42; 41–44 in comparative specimens); precaudal vertebrae 53–57 (mainly 54–56); and total vertebrae 172–181 (169–180 in comparative specimens).

Teeth moderately large, conical ( Fig. 6 B ). Intermaxillary teeth curved, in about three or four 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 with 2 (rarely 1 or 3) enlarged teeth on midline, with 2 smaller teeth directly behind, side by side; a few additional small teeth in front and behind, no teeth laterally.

Coloration. When fresh, body mostly light grayish or pinkish gray with ventral surface paler. Vertical fins pale anteriorly, gradually becoming blackish posteriorly and entirely back at posterior fourth of body; caudal fin black. Slightly paler in preservation. Stomach black internally and pale externally, covered with many black dots on outer surface; intestine black or brown internally and externally. Mouth cavity and gill chamber pale; lower 2/3 of peritoneum silver white, gradually covered by denser pepper dots on dorsal 1/3 dorsally with some large black dots may present.

Distribution. This species is known from two widely separated locations: Japan to the Philippines in the northwestern Pacific, and the southwestern Indian Ocean.

Remarks. Castle & Smith (1999) re-assessed the genus and diagnosed B. wallacei as: 168–180 total vertebrae and two enlarged teeth followed by 2 or 3 smaller teeth on vomer. We counted our specimens with 172–181 total vertebrae.

The pattern of vomerine teeth in this species is quite distinctive. There are one or two enlarged teeth on the midline followed directly behind by two smaller teeth arranged side by side. There are usually a few smaller teeth in front or behind those mentioned, but there is no consistent pattern of numerous smaller teeth on both sides of the median teeth. Although there are a few small teeth that extend from each side of the maxillary teeth in the specimens we examined, there is always a space on the lateral side of the vomerine tooth patch that clearly separates it from the maxillary teeth.

Based on HCH’s long-term observations, B. wallacei is one of the most common and abundant eel species in the bycatch of bottom trawls in Taiwan. Other common eel species are Rhynchoconger ectenurus , Uroconger spp., Conger macrocephalus, Ariosoma meeki (Congridae) ; Dysomma spp. ( Synaphobranchidae ); and Ophichthus urolophus , Pisodonophis spp. ( Ophichthidae ).

Comparative materials. Bathycongrus guttulatus : USNM 92344 (1, 566). USNM 93356 (3, 343–350). USNM 93357 (1, 530). USNM 93358 (1, 462). USNM 93362 (1, 530). Bathycongrus wallacei : Japan: FAKU 25140 (1, 374). FAKU 27870 (1, 354). USNM 177762 (1, 485). The Philippines: USNM 135253 (1, 260). CAS 34533 (1, 191). Bathycongrus retrotinctus : Japan: USNM 49974 (1, 247). USNM 59787 (1, 222). USNM 117983 (2, 268–288). USNM 117995 (1, 341). USNM 163371 (1, 304+). USNM 163372 (1, 389). The Philippines: USNM 92345 (1, 331). USNM 93295 (1, 95). USNM 135236 (3, 220–335). USNM 135240 (2, 160–270). USNM 135242 (1, 336). USNM 135246 (1, 290). USNM 135249 (1, 192). USNM 135251 (1, 314). CAS 40910 (1, 350). CAS 34435 (1, 262).

Figures

FIGURE 1. Illustration of head pore systematic of a typical Bathycongrus. AN, anterior nostril; IO, infraorbital pores; LL, Lateral-line pores; PN, posterior nostril; POM, preopercular-mandibular pores; SO, supraorbital pores; ST, supratemporal pore (arrowed).

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 11. Bathycongrus wallacei (Castle, 1968), NMMB-P29130, 428 mm TL.