Obelia geniculata (Linnaeus, 1758)

Galea, Horia R., 2010, Notes on a small collection of thecate hydroids (Cnidaria: Hydrozoa) from Tristan da Cunha, south Atlantic, Zootaxa 2336, pp. 1-18 : 13

Obelia geniculata (Linnaeus, 1758)

( fig. 5 H)

Sertularia geniculata Linnaeus, 1758: 812 .

Obelia geniculata – Cornelius, 1975: 272, figs 1 , 5 . – Cornelius, 1995b: 301, fig. 70.

Material examined. Stn. T14, 23.ii.2005: several sterile, poorly-preserved stems, up to 10 mm high, on Macrocystis pyrifera .

Distribution. Previously collected by the S.Y. Scotia from the fronds of Macrocystis pyrifera at Gough Island (Ritchie 1907). This is a near-cosmopolitan species, penetrating high latitudes in the northern hemisphere and into sub-Antarctic waters in the southern hemisphere (Medel & Vervoort 2000).

Figures

FIGURE 1. Map of the Tristan da Cunha archipelago, with the location of stations yielding hydroid material.

FIGURE 5. A to C: Plumularia setacea (Linnaeus, 1758) – stem internode and basal part of cladium (A); female gonotheca (B); stolonal nematothecae (C). D: Silicularia rosea Meyen, 1834 – hydrotheca (middle), female (left) and male (right) gonothecae. E: Clytia gracilis (M. Sars, 1850) – hydrotheca atop its pedicel. F: Clytia paulensis (Vanhöffen, 1910) – hydrotheca atop its pedicel. G: Obelia dichotoma (Linnaeus, 1758) – fragment of stem with hydrotheca. H: Obelia geniculata (Linnaeus, 1758) – stem internode with hydrotheca. Scale bars: 100 µm (C); 200 µm (G); 300 µm (A, B, F, H); 400 µm (E); 1 mm (D).