Oswaldella delicata Pena Cantero, Svoboda & Vervoort 1997

Oswaldella delicata Peña Cantero, Svoboda & Vervoort, 1997

(Figs 2, 16 B, 17B, 19B)

Material examined. Spanish Antarctic Expedition Bentart 95: Stn 28A, BIO Hespérides, 2 February 1995, 62°12.1297’S, 60°23.1833’W (South Shetland Islands, north of Livingston Island), 126 m (Department of Zoology, University of Valencia, BENTART 95-28A).

Description. Monosiphonic, unbranched stems, up to 60 mm high, divided into internodes. Angle between cauline apophyses and stem ca. 45°. Cauline apophyses with single axillary nematophore, emerging through perisarc hole provided with very short collar-shaped nematotheca (Fig. 2 B, C).

Hydrocladia unbranched (Fig. 2 A), some bifurcated. First hydrocladial internode bifurcated, with two similar prongs. Mesial superior nematophore emerging behind free part of adcauline hydrothecal wall. Mesial inferior nematophore on a strongly marked swelling at proximal third of internode; with well-developed, nail-shaped nematotheca (Fig. 2 D–F). Hydrotheca elongate, placed on middle of internode. Adcauline wall with distinct free portion. Abcauline hydrothecal wall roughly straight, but basally convex (Fig. 2 E). Hydrothecal aperture circular, more or less perpendicular to long axis of internode (Fig. 2 D–E); rim even.

Gonothecae fusiform with subterminal circular aperture.

Remarks. Our study has confirmed the presence of a single axillary nematophore in the cauline apophyses, as previously described (Peña Cantero et al. 1997; Peña Cantero & Vervoort 2004). However, it is noteworthy that our study has provided evidence of the presence of a little-developed, previously unnoticed, collar-shaped nematotheca associated with that nematophore (Fig. 2 B–C).