Nemertesia ramosa

Nemertesia ramosa (Lamarck, 1816)

(Fig. 9F–H)

Nemertesia ramosa — Ansín Agís et al., 2001: 215 –222, figs 83–84 (synonymy).

Material examined. 9778#1, a fragmented stem (largest fragment 160 mm long), no gonothecae.

Description. Stem branched and polysiphonic, broken into several fragments; longest fragment, the basal one, with hydrorhiza and completely polysiphonic, c. 160 mm long.

Branching more or less in one plane and mostly alternate. Lower-order stems polysiphonic in part of their extension; at least third-order stems present.

Stem divided into internodes and with alternating verticils of three apophyses, giving rise to six longitudinal rows. Each cauline internode usually with a single whorl at distal end; double internodes with two verticils of apophyses also present.

Apophyses supporting hydrocladia and provided with one mamelon and three pairs of nematothecae (Fig. 9F): one at base of apophysis, a second pair in the middle and a third one at distal part.

Hydrocladia homomerously divided into hydrothecate internodes (Fig. 9G–H). Each with one hydrotheca and four nematothecae (Fig. 9H): two flanking hydrothecal aperture, one mesial inferior nematotheca and one mesial superior nematotheca. Hydrocladial internodes with basal and distal perisarc ring.

Hydrotheca on lower half of internode (Fig. 9G–H). Hydrotheca low (Fig. 9H), about as high as wide (abcauline length 130 µm, diameter at aperture 120 µm). Abcauline wall longer than adcauline one and, consequently, hydrothecal aperture tilted adcaudally.

Ecology and distribution. Eurybathic species, found at depths between 3 (Gili et al. 1987) and 1425 m (Bedot 1921); our material was collected at 1016–1055 m.

According to Ramil & Vervoort (2006), Nemertesia ramosa is widely distributed in tropical, subtropical and temperate East Atlantic; from Norway and Faeroes to South African coast, reaching Mozambique in the Indian Ocean. Our material comes from the Porcupine Seabight.