Oligobregma blakei, Schüller, Myriam & Hilbig, Brigitte, 2007

Schüller, Myriam & Hilbig, Brigitte, 2007, Three new species of the genus Oligobregma (Polychaeta, Scalibregmatidae) from the Scotia and Weddell Seas (Antarctica), Zootaxa 1391, pp. 35-45 : 37-38

Oligobregma blakei sp. nov.

( Fig. 1 A–E)

Holotype. Scotia Sea, northeast off Elephant Island, Sta. 46­7, 30 January 2002, 60°38.35’S, 53°57.36’W, 2889–2892 m, EBS ( ZMH, P­ 24732).

Etymology. The species is named after J.A. Blake, whose monograph about the Scalibregmatidae of the Southern oceans contributed immensely to this study.

Diagnosis. The distinguishing character of this species is the presence of acicular spines in the first and second notopodia arranged in single rows.

Description

Holotype of medium size, 3 mm long and 0.5 mm wide for 19 segments; posterior segments regenerating ( Fig. 1 A). Colour in alcohol: white to a light tan; body anteriorly expanded.

Prostomium bearing 2 rounded lobes anterolaterally; no eyes; nuchal organs not apparent; peristomium well developed, achaetous ( Fig. 1 B).

Anterior 4 chaetigers smooth, lacking annulations; chaetigers 5–7 triannulated, subsequent chaetigers quadriannulated; parapodia of anterior segments reduced to simple lobes, becoming more distinct in median and posterior region; median and posterior ventral and dorsal cirri short and conical ( Fig. 1 C); interramal sense organs not apparent.

Acicular spines present in notopodia of chaetigers 1 and 2, accompanied by simple capillaries; spines smooth and sickle­shaped ( Fig. 1 D), arranged in single rows; long, simple capillaries in both rami of all chaetigers; small furcate chaetae present from chaetiger 4, covered by a fringe of short hairs ( Fig. 1 E); length of tynes unequal, one tyne about twice as long as other.

Pygidium terminal, trilobate, without cirri ( Fig. 1 A).

Remarks. The species is only represented by the holotype. Its posterior end is in the process of regeneration. Posterior chaetigers might therefore differ from additional specimens of this species. The description of anterior characters, however, is sufficient to define a species within the genus Oligobrema since the arrangement of the acicular spines, the surface texture of anterior segments, and the presence of eyes and nuchal organs are the most important traits. Oligobregma blakei sp. nov., is most closely related to O. pseudocollare sp. nov. The species bears only one row of acicular spines each in chaetigers one and two, while spines of O. pseudocollare sp. nov., are arranged in two rows. Therefore it is undoubted that the present specimen belongs to a new species.

Distribution. Scotia Sea, in 2889–2892 m.

Figures

FIGURE 1. A­E. Oligobregma blakei sp. nov. — holotype (ZMH). A. entire animal, lateral view; B. anterior segments, dorsal view; C. posterior parapodium; D. acicular spine; E. furcate chaeta.