Nannobrachium phyllisae Zahuranec 2000

Nannobrachium phyllisae

Lampanyctus achirus.—Bussing, 1965:203–204 [in part] [midwaters of Peru-Chile Trench].—Craddock and Mead, 1970:28 [in part] [southeast Pacific].—Parin, 1971:82, 87, 89, 90 [in part?] [Peru Current].—Parin et al., 1973:114, 115 [?in part] [eastern tropical Pacific].—Wisner, 1976:177–180 [in part] [discussion, fig. 166A],—[Not Andriashev, 1962.]

TYPE SPECIMENS.—Holotype: Male, 108 mm, WHOI, Anton Bruun Cruise XIII, sta 52, 33°24′S, 73°33′W to 33°32′S, 73°35′W, 01 February 1966.

Paratypes: SIO 52–372, 2 (83–92 mm); SIO 63–1013, 2 (74–88 mm); SIO 63–1014, 1 (65 mm); SIO 65–667, 4 (112–147 mm); SIO 68–320, 1 (85 mm); SIO 69–321, 1 (28 mm); SIO 69–330, 7 (26–84 mm); USNM 303164, 3 (31–35 mm); USNM 303310, 5 (97–149 mm); WHOI 1344, 1 (39 mm); WHOI 1359, 1 (126 mm).

COMPARATIVE DIAGNOSIS.—Nannobrachium phyllisae (Figure 20) can be distinguished from N. achirus by its lower number of AO photophores, gill rakers, tooth patches, infracaudal luminous gland scales, lateral line organs, and vertebrae (Table A11); however, in all characters, there is overlap in ranges of counts. Similar differences are found between N. phyllisae and N. wisneri, namely, N. phyllisae has a lower number of infracaudal luminous glands and fewer vertebrae but has one more gill raker on the upper limb of the first gill arch. Nannobrachium phyllisae, however, can be separated from both N. wisneri and N. hawaiiensis by the presence of pectoral fins in small specimens (up to about 50 mm). It can be further separated from N. hawaiiensis, as well as from N. crypticum, by its higher AO photophore, gill raker, lateral line organ, and vertebral counts. It can be separated from all other species of Nannobrachium by the combination of characters in Table 1.

DESCRIPTION.—Counts are based on up to 21 specimens from the eastern Pacific Ocean and are given in Tables A2–A8, A11. Counts for the holotype are D 16, A 20, P1 none, GR 4+12, tooth patches 9, AO 7+7, SC/IC 3/i+5, LL 34, V 15+21.

Proportions: Given in Table 16. Holotype measurements as follows: SL 108, AD 18.6, PDD 19.5, CPD 11.4, CPL 21.6, PADL 20.5, PDL 53.5, PPL 41.4, PANL 56.2, PAL 12.9, HL 31.4, UJL 22.7, SOL 5.0, ED 5.2, SGL 5.3, IGS 12.1, IGEL 13.9, AFB 28.7, DFB 21.7, AF 8.7.

Fins: Origin of anal fin under middle of dorsal-fin base. Pectoral fins relatively long and well developed in juvenile stages (easily visible in specimens up to about 50 mm), progressively becoming relatively shorter, with thicker rays, (covered by skin in various stages of becoming vestigial, between about 40–70 mm); vestigial rays buried in skin and not externally visible. Largest adults with vestigial pectoral-fin elements undetectable (perhaps lost through resorption). Adipose fin over end of anal-fin base.

Luminous Organs: PLO 1–2 photophore diameters below lateral line (slightly more than 1 in holotype). PO4 on level of PVO2 (above level in holotype) and above PO3. PVO1–2 interspace wide, that distance 2–3 times into PVO2-PLO distance (about 2 times in holotype). SAO1 above VO2–3 interspace (slightly closer to VO2 in holotype) SAO2 above VO4-AOa1 interspace but usually closer to AO1 (notably closer to AOa1 in holotype). SAO3 behind vertical from AOa1. AOa1 not noticeably depressed; AOa1–2 interspace only very slightly enlarged, if at all. AOp1 above end of anal-fin base (slightly behind end in holotype). Pre slightly separate from AOp; Prc1–2 on horizontal line; Prc3 below Prc4 but variable, although frequently behind vertical from Prc4 (Prc3 on vertical from posterior margin of Prc4 in holotype). Supracaudal and infracaudal luminous glands well developed, commonly having single separated luminous scale preceding solid infracaudal gland. Secondary photophores not found.

Size: Nannobrachium phyllisae is a large species, reaching a maximum size of at least 151 mm based on examined material. Wisner (1976), in discussing the Lampanyctus achirus species complex, listed a maximum size of about 155 mm for specimens from the southeast Pacific, which probably included this species.

Material: 30 (28–151 mm) specimens, excluding type material.

VARIATION.—Nannobrachium phyllisae is restricted to the Peru-Chile Current area of the southeastern Pacific Ocean (Figure 19). As might be expected for a species with such a restricted geographic range, no consistent geographic variability was found in specimens examined from different parts of the range.

ETYMOLOGY.—I have the pleasure of naming this species in honor of my former wife Phyllis E. Fabian, as a token of recognition for her many years of support, which culminated in this study.