Nannobrachium bristori Zahuranec 2000

Nannobrachium bristori

Lampanyctus niger.—Berry and Perkins, 1966:662 [?in part] [fide H.G. Moser; Pacific off California and northern Mexico].—Moser and Ahlstrom, 1974: 406–407 [larva figured].—[Not Günther, 1887.]

Lampanyctus niger (Form C).—Clarke, 1973:416, 418 [ecology north of Hawaii].—[Not Günther, 1887.]

Lampanyctus (Lampanyctus) niger.—Bekker, 1983:87–89, 198–200 [?in part?] [key, description, distribution],—[Not Fraser-Brunner, 1949]

Lampanyctus sp.—Moser et al., 1984:238, fig. 124D [larva figured].

Nannobrachium “niger”—Moser and Ahlstrom, 1996:418–419 [early life history and larvae illustrated].

TYPE SPECIMENS.—Holotype: Male, 110 mm, SIO 71-301, 27°26.6′N, 155°24.6′W, 30 September 1971.

Paratypes: HIMB 70–913, 2 (34–67 mm); HIMB 70–914, 18 (21–40 mm); HIMB 70–916, 4 (33–40 mm); HIMB 70–927, 2 (58–86 mm); OS 12816, 1 (74 mm); OS 12815, 4 (33–116 mm); SIO 51–84, 1 (57 mm); SIO 66–20, 2 (72–76 mm); SIO 67–56, 1 (73 mm); SIO 71–301, 3 (40–120 mm); SIO 71–310, 1 (111 mm); SIO 73–145, 1 (142 mm); SIO 73–160, 1 (105 mm); SIO 76–6, 1 (46 mm); SIO 73–329 (28°03′N, 154°39′W, 22 June 1973), 1 (68 mm); USNM 298174, 8 (30–91 mm); USNM 298191, 1 (101.5 mm); USNM 298192, 2 (32.5–47 mm); USNM 359634 (25°02′N, 137°55′W, 19 Nov 1967), 1 (106 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium bristori (Figure 14) can be most easily distinguished from the other species in the Regale group by its number of AO photophores (fewer than in N. ritteri, more than in N. idostigma), number of gill rakers and lower limb tooth patches on the second gill arch (more of both than in N. regale and N. ritteri, more tooth patches than in N. idostigma), and number of infracaudal luminous gland scales and lateral line organs (fewer of both than in N. regale and N. ritteri, fewer lateral line organs than in N. fernae and more than in N. idostigma) (Table A9) Nannobrachium bristori can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 23 specimens from the North Pacific Ocean and are given in Tables A2–A9. Counts for the holotype are D 14, A 18, P1 16?, GR 4+11, tooth patches 9, AO 5+7 (L), 6+7 (R), SC/IC ?, LL 37?, V 16+21.

Proportions: Given in Table 12. Holotype measurements (in mm) as follows: SL 110, HD 17.5, PDD 17.7, CPD 9.6, CPL 26.4, PADL 24.3, PDL 47.0, PPL 41.0, PANL 58.5, PAL 16.3, HL 31.3, UJL 22.9, SOL 4.9, ED 6.4, SGL 4.9, IGS 7.6, IGEL 7.6, AFB 26.4, DFB 21.7, AF 7.6.

Fins: Origin of anal fin behind middle of base of dorsal fin. Pectoral fins reaching just beyond PO3 with weak and flexible rays. Adipose fin above end of anal-fin base.

Luminous Organs: PLO 1–2 photophore diameters below lateral line (1 diameter in holotype). PO4 approximately on level of PVO2 and above, or more frequently slightly behind, vertical from PO3 (PO4 behind vertical from PO3 in holotype). VLO 2–3 photophore diameters below lateral line (VLO 2 diameters below in holotype); its distance to lateral line equal to or greater than distance of PLO to lateral line. SAO2 midway between VO4 and AOa1, exact position variable, but frequently closer to AOa1, (SAO2 closer to VO4 in holotype). AOp1 at or behind end of anal-fin base (AOp1, slightly behind end of base in holotype). Pre separate from AOp; Prc12 on horizontal line; Prc34 on vertical or nearly vertical line, more than 1 photophore diameter behind vertical from Prc2 (Prc4 slightly behind vertical from Prc3, 2 photophore diameters behind vertical from Prc2 in holotype). Supracaudal and infracaudal luminous glands well developed, infrequently having single separated luminous scale preceding solid infracaudal gland. No secondary photophores found.

Size: Nannobrachium bristori is a large-bodied species, reaching a maximum size in excess of 140 mm. The largest specimen encountered was 142 mm.

Material: 98 (16–126 mm) specimens were examined, excluding type material.

VARIATION.—Nannobrachium bristori appears to be restricted to the tropical and subtropical waters of the North Pacific (Figure 10). It does not seem to be a particularly abundant species. Most collections contain only one or a few specimens.

No significant geographic variation could be found in N. bristori, however, the gill-raker count appears to exhibit higher variance than other species of Nannobrachium, but the cause of this variation is unclear.

ETYMOLOGY.—Named for my good friend, the late William B. Bristor, Jr., of Washington, D.C.

The Cuprarium Groupa

All species in this group share the unique character of dense black pigmentation on the posterior tips of both the supracaudal and infracaudal luminous glands. The pigmentation looks like a black “hood” or “cap” and somewhat resembles the caudal gland pigmentation of some species in the genera Taaningichthys and Lampadena. The pigmentation in the species of the Cuprarium group, however, is more weakly developed, and the structure appears to be more fragile than in those genera. Consequently, it may be missing in damaged specimens.

Pectoral-fin length in the species of this group is intermediate. The pectoral fins are longer than one-half the distance from the pectoral-fin base to the pelvic-fin insertion, but they never reach the pelvic-fin insertion. The pectoral rays resemble those of the Regale group species, but coincident with the slightly shorter fin length, the rays are proportionally thinner and more flexible.

Other shared characters not unique to this group include (1) VLO usually touching lateral line, (2) posterior position of SAO1 above the VO34, interspace, usually at a slightly lower level than SAO2, (3) Prc3 on a vertical midway between Prc2 and Prc4, and (4) Pol2 usually well forward of vertical from adipose fin origin.

These and other characters are compared in Table 1 for all species groups of Nannobrachium.

The Cuprarium group contains two species: Nannobrachium cuprarium (Tåning, 1928) and N. lineatum (Tåning, 1928).

Modal characters of all species in the Cuprarium group are listed in Table A10 along with those for N. isaacsi, the only species in the Isaacsi group.