Orbiniella andeepia Narayanaswamy & Blake 2005

Orbiniella andeepia Narayanaswamy & Blake, 2005

Figure 57

Orbiniella andeepia Narayanaswamy & Blake, 2005: 843 –846, fig. 1.

Material examined.—Drake Passage, ANDEEP I ANT XIX-3, R/V Polarstern, Sta. PS-61/114-7, 2900 m (1, JAB).—Weddell Sea, ANDEEP II ANT XIX-4, R/V Polarstern, Sta. PS-61/139- 10, 3965 m (1, ZMH P-27801); PS-61/141- 7, 2260 m (1, ZMH P-27802); ANDEEP III ANT XXII-3, R/V Polarstern, Sta. PS-67/110-4, 4700 m (1, SEM, JAB); Sta. PS-67/110- 5, 4702 m (1, ZMH P-27803); Sta. PS-67/121- 10, 2663 m (1, ZMH P-27804); Weddell Sea, abyssal plain, ANDEEP SYSTCO ANT XXIV-2, R/V Polarstern, Sta. 33- 14, 5338 m (1, ZMH P- 27805).

Description. A large specimen from ANDEEP III Station PS-67, 11– 12 mm long, 0.6 mm wide for 68 normal setigerous segments and four setigers as part of a narrow regenerating posterior pygidial end. Morphology of prostomium and peristomium same as originally reported for smaller specimens.

Prostomium broadly rounded anteriorly (Fig. 57 A), exhibiting methyl green staining reaction; peristomium with two achaetous rings (Fig. 57 A). Eyespots absent; two pigmented nuchal organs present. First 12 setigers narrower than following ones suggesting a weak differentiation of body into thoracic and abdominal regions. Each setigerous segment with prominent encircling glandular ridge or ring encompassing dorsum, venter, and parapodia; this ring occupying most of surface of narrower anterior segments, then restricted to posterior one-third of longer abdominal segments; glandular ring with a weak methyl green staining reaction. Each notopodium with a short post-setal lamella (Fig. 57 C), smaller than originally reported, but proportional in size on larger specimens; neuropodial lamellae absent.

Setae including crenulated capillaries in both noto- and neuropodia (Fig 57 B); 1–2 spines occurring in notopodia and neuropodia; spines smooth and pointed (Fig. 57 C). Branchiae absent. Narrow posterior end appears to be regenerating; anal cirri absent.

Remarks. The larger specimens found at Sta. PS 67 110-4 confirm the generic placement of Orbiniella andeepia. If the original specimens had been juveniles of a larger orbiniid then adult characters of other genera would have been present in the large specimen. There is no evidence of elevated abdominal parapodia as characterizes most other orbiniids. Furcate setae and branchiae are entirely absent. The methyl green staining reaction of the prostomium and the encircling segmental ring is newly reported.

Of the four deep-water species of Orbiniella in Table 2, all have noto- and neuropodial acicular spines. Of these, O. andeepia and O. petersenae have notopodial lamellae while O. hobsonae and O. aciculata do not.

Orbiniella hobsonae has crenulated acicular spines instead of smooth spines as in the other three species. Orbiniella aciculata and O. petersenae have two and four anal cirri, respectively; O. andeepia and O. hobsonae have none. Orbiniella andeepia is the only deep-water species of Orbiniella in the Southern Ocean.

Distribution. Southern Ocean in slope and abyssal depths, 2257–5338 m.