Orbiniella eugeneruffi, Blake, 2020

Blake, James A., 2020, New species and records of deep-water Orbiniidae (Annelida, Polychaeta) from the Eastern Pacific continental slope, abyssal Pacific Ocean, and the South China Sea, Zootaxa 4730 (1), pp. 1-61 : 41

Orbiniella eugeneruffi new species

Figure 20

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Material examined. South China Sea, off Brunei, Island of Borneo, Site CA1 , R / V Emma , coll. J.A. Blake, box corer, Sta. 45, 2 Jun 2011, 5°48.965′N, 114°17.317′E, 1260 m, holotype ( MCZ 153578 ) ; Sta. 49, 2 Jun 2011, 5°44.405′N, 114°13.993′E, 1199 m, 1 paratype ( MCZ 153579 )

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Description. A small species, holotype complete with 18 setigers, 4.0 mm long and 0.6 mm wide across midbody; paratype complete with 21 setigers, 6.1 mm long, 0.5 mm wide. Body more or less oval in cross section; segments short, about five times wider than long. All parapodia lateral; posterior segments not elevated or modified. Dorsal and ventral grooves absent; venter with mid-ventral ridge formed of lobes along the ventral mid-line of each segment ( Fig. 20B ). Individual segments with narrow transverse intersegmental groove ( Fig. 20 A–B); groove of middle segments weakly expanded into 1–2 transverse annuli, best observed dorsally ( Fig. 20A ). Color in alcohol: white.

Pre-setiger region about as long as first two setigers, but about one-third narrower. Prostomium broadly rounded on anterior margin, about as long as wide ( Fig 20A ); eyespots absent; nuchal organs not observed. Peristomium with two annular rings, separated from one another, first ring shorter than second ( Fig. 20 A–B), forming posterior lip of mouth ( Fig. 20B ). Both rings with a few lobes on anterior margin.

Branchiae entirely absent. Noto- and neuropodia conical, setae emerge from distal tip; postsetal lobes or lamellae entirely absent ( Fig. 20D ). Setae include capillaries and acicular spines; furcate setae absent. Capillaries from setigers of first half of body numbering 5–7 per fascicle; all long with a distinct row of barbs or camerations along one edge ( Fig. 20D ); capillaries of posterior segments reduced to 3–4 per fascicle; all long, but relatively smooth, with barbs either absent or only irregularly present. Acicular spines include one in notopodia and 1–2 in neuropodia; each spine smooth, thick, narrowing to pointed tip ( Fig. 20D ).

Pygidium narrow, with four short anal cirri ( Fig. 20C ).

Methyl green stain. No pattern, de-stains rapidly.

Remarks. By lacking postsetal lobes or lamellae and having smooth instead of serrated acicular spines, Orbiniella eugeneruffi n. sp. is most closely related to O. aciculata Blake, 1985 from near hydrothermal vents at the Galápagos Rift. Both species also have the first of two peristomial rings shorter than the second. The two species differ in that O. aciculata has 1–4 acicular spines in the noto- and neuropodia and two anal cirri, whereas O. eugeneruffi n. sp. has only one spine in the notopodia and 1–2 in the neuropodia and four anal cirri.

Etymology. This species is named for the late Mr. Robert Eugene Ruff, polychaete systematist and long-time friend and colleague. Eugene was part of a select taxonomic team that was developed by the author to identify polychaetes from offshore and deep-sea surveys, including those from off Brunei.

Distribution. South China Sea, off Brunei, Island of Borneo, 1199–1260 m.

Figures

FIGURE 20. Orbiniella eugeneruffi n. sp. Holotype MCZ 153578): A, anterior end, dorsal view; B, anterior end, ventral view; C, posterior end, dorsal view. Paratype (MCZ 153579): D, mid-body setiger, anterior view (inset not to scale).