Oswaldella grandis Pena Cantero, Svoboda & Vervoort 1997

Oswaldella grandis Peña Cantero, Svoboda & Vervoort, 1997

(Figs 7, 16 G, 17G, 19G)

Material examined. Spanish Antarctic Expedition Antártida 8611: Stn NA 172, 61°01'S – 60°58'S, 55°34'– 55°56'W (Elephant Island, South Shetland Islands) (Department of Zoology, University of Valencia, ANT NA 172).

Description. Polysiphonic, unbranched stems, up to 500 mm high, usually divided into internodes. Angle between cauline apophyses and stem ca. 45°. Cauline apophyses with four to five nematophores, two to three axillary ones, each emerging through simple hole in perisarc, and other two nematophores, each emerging through ‘mamelon’ (Fig. 7 B–C).

Hydrocladia much branched (Fig. 7 A), with up to third-order hydrocladia. First hydrocladial internode bifurcated (Fig. 7 A), with two similar prongs. Mesial-inferior nematophore typically with much reduced nematotheca, though not existent in present material (Fig. 7 D–F). Unforked hydrocladial internodes without infrathecal swelling. Hydrotheca placed on distal half of internode (Fig. 7 D–E). Hydrotheca low, about as high as wide. Abcauline hydrothecal wall straight. Hydrothecal aperture circular, perpendicular to longitudinal axis of internode; rim even (Fig. 7 D–E).

Male gonothecae almost cylindrical, with subterminal opening. Female larger, club-shaped, with subterminal aperture.

Remarks. Peña Cantero & García Carrascosa (1995) did not find any mesial inferior nematothecae when they examined this material, a pattern corroborated herein by SEM analysis. As Peña Cantero & García Carrascosa (1995) indicated, this could be related with the poor condition of the material with just a few hydrocladia left.

Until now only two axillary nematophores in the cauline apophyses had been described for this species. However, we observed three with the central one being larger and sometimes with the appearance of being the result of coalescence of two central ones (Fig. 7 C).