Bathyuroconger Fowler, 1934

Smith, David G., Ho, Hsuan-Ching & Tashiro, Fumihito, 2018, Eels of the genus Bathyuroconger in the northwestern Pacific, with descriptions of four new species (Anguilliformes: Congridae), Zootaxa 4454 (1), pp. 147-167 : 148-149

Genus Bathyuroconger Fowler, 1934

Bathyuroconger (subgenus of Uroconger ) Fowler, 1934:273 (type species Uroconger braueri Weber & de Beaufort, 1916 , by original designation).

SilveSterina Fowler, 1934:274 (type species SilveSterina parvibranchialiS Fowler, 1934 by original designation).

Characters. Body moderately elongate, preanal length 33‒42% TL, tail slender and attenuate; rather delicate in composition, remaining quite limp in preservative; skin thin, slimy, rather transparent and loosely attached. Dorsal fin beginning over or slightly behind base of pectoral fin. Gill opening variable, from semi-circular, moderate in size, with upper corner touching base of pectoral fin to a small pore widely separated from fin.

Head large and robust in comparison to body; mouth terminal, jaws nearly equal or upper jaw slightly projecting; fleshy part of snout not projecting beyond intermaxillary teeth; labial flange absent from both jaws. Anterior nostril in a short tube, near tip of snout, directed anterolaterally; posterior nostril small, round, in front of eye at mid-eye level.

Lateral line complete. Head pores moderate to large in size, not greatly enlarged or slit-like ( Fig. 1 ); supraorbital with 3 pores (rarely 4), all at tip of snout; infraorbital with 5 pores, first pore (adnasal) above anterior nostril, three pores along upper jaw and 1 behind rictus; no pores behind or between eyes; mandibular with 7 pores (rarely 6 or 8), 6 pores along lower jaw and 1 behind rictus; preopercular with 3 pores; 1 single pore on supratemporal canal.

Teeth strong, fang-like ( Fig. 2 ). Intermaxillary teeth enlarged, in two transverse rows, separated from maxillary and vomerine teeth. Vomerine teeth few, usually 1 or 2 enlarged median teeth, with a few small teeth around and behind them; the vomerine tooth patch relatively short. Maxillary teeth in narrow bands, wider anteriorly, the outer teeth largest. Dentary teeth in two or three irregular rows, the anterior outer teeth enlarged.

Color variable, from dark brown to light gray. Smaller specimens often with two or three rows of small melanophores along the body, presumably the remains of larval pigment.

Remarks. Although it has been commonly compared and confused with Uroconger , the relationships of Bathyuroconger clearly lie with Bathycongrus . Uroconger is easily distinguished by its long single row of vomerine teeth, which extends nearly the entire length of the upper jaw. Bathyuroconger and Bathycongrus , in contrast, have a short vomerine tooth patch restricted to the anterior end of the mouth, commonly with one or a few enlarged teeth with smaller teeth around them. The remains of the larval pigmentation, commonly seen in small specimens, consists of three irregular longitudinal rows above, on, and below the mid-line, similar to the pattern seen in larvae of Bathycongrus ( Castle, 1969) . Larval Uroconger have a single midlateral row of melanophores ( Nair, 1946; Nair & Mohamed, 1960; Smith, 1989b:751). Bathyuroconger differs from Bathycongrus primarily in the relatively large and deep head, larger teeth, the equal length of the upper and lower jaws, and the more delicate and easily damaged body.

Figures

FIGURE 1. Demonstration of head pores of Bathyuroconger species. GO, gill opening; IO, infraorbital pores; LL, lateral-line pores; M, mandibular pores; POP, preopercular pores; SO, supraorbital pores; ST, supratemporal pore (indicated by arrow). From B. parvibranchialiS, ASIZP 63789.

FIGURE 2. Demonstration of tooth pattern of Bathyuroconger species. A. upper jaw, arrow indicates first SO pore on each side. B. lower jaw. From B. albuS sp. nov., NMMB-P11157, paratype.