Dysponetus profundus

Dysponetus profundus was originally described from the Angola and Guinea Basins, at depths of 3991 – 5655 m (Böggemann 2009). The specimens reported here were recovered in hemipelagic silty clay with foraminiferans collected from a topographic high in the vicinity of the SW Iberian margin fault lineaments (Hensen et al. 2015). The present study extends the geographical distribution of this species to the Horseshoe Abyssal Plain (SW Iberian margin; Fig. 1), at a depth of 4864 m.

Material examined PORTUGAL • 2 af; Horseshoe Abyssal Plain; 35 ° 47.265 ′ N, 10 ° 38.499 ′ W; 4864 m; St M 86 - 5 _ 366; DBUA 0002278. Description Two tiny and incomplete specimens, with five chaetigers each (about 0.40 mm long). Notochaetae long, bright and translucent, covering dorsum from chaetiger 5. Prostomium rounded, without eyes. Palps and antennae globular. Pharynx visible through body wall, extending to segment 5, with a pair of slender light brown stylets, visible through body wall. First segment reduced, with two pairs of globular tentacular cirri. Following segments with biramous parapodia, noto- and neurochaetae. Notopodial lobes as low mounds. Neuropodial lobes cylindrical, larger than notopodia. Dorsal cirri globular on segment 2 (chaetiger 1), becoming elongated posteriorly. Ventral cirri missing in all parapodia. Notochaetae spine-like, robust, internally chambered, with two longitudinal rows of short alternating spinelets. Neurochaetae with internally chambered shafts and very finely serrated blades with minute bidentate tips; blades variable in length. Ecology and distribution