Silicularia rosea Meyen 1834

Silicularia rosea Meyen, 1834

(Fig. 1 M– O, Table 2)

Silicularia rosea Meyen, 1834: 204, pl.35 Figs 1 –11.― Hartlaub, 1905: 572, Fig. T1.

Material examined. HF9, Los Gemelos, lat. -54.91942, long. -67.36308, 14.xii.2010, 0 m, sample C066: female colony on fragment of Macrocystis pyrifera (MHNG-INVE-86240); 15.xii.2010, 13 m, sample C131: male colony on fragment of M. pyrifera (MHNG-INVE-86239). Tristan da Cunha, Stonyhill Point, lat. -37.17130, long. - 12.26315, 23.ii.2005, 15– 44 m: small male and female colonies of S. hemisphaerica (Allman, 1888) on pieces of M. pyrifera (NHM 2009.26).

Remarks. The present material from Chile was compared with that described earlier by one of us from Tristan da Cunha (Galea 2010a). The most striking difference is to be found in the comparatively larger size of the South- American material (Table 2). The hydrothecae in these specimens exhibit nearly the same shape, but at a different scale, and their cnidome composition appears uniform within the genus3. However, the female gonothecae from Tristan da Cunha are swollen basally and taper gradually towards the aperture, while those from Chile have the lateral walls nearly parallel throughout. In addition, their size differences are striking (compare Fig. 1 N and 1Q), and this feature is also displayed by the male gonothecae (compare Fig. 1 O and 1R).

On one hand, the Chilean material corresponds to the illustration of the type of Silicularia rosea Meyen, 1834 given by Hartlaub (1905), as well as to Hypanthea aggregata Allman, 1888, H. georgiana 4 Pfeffer, 1889, and H. repens Allman, 1876. Consequently, we assign the present material to Meyen’s species, and consider the three other nominal species as conspecific.

On the other hand, the Tristan da Cunha specimens seem indistinguishable from the nominal species Hypanthea atlantica 5 Marktanner-Turneretscher, 1890, in both morphology and size (Table 2), and are also probably conspecific with H. hemisphaerica Allman, 1888 from the Falkland Islands. The Gough Island material assigned by Ritchie (1907) to S. hemisphaerica also agrees in size with the Tristan da Cunha specimens. Owing to the smaller size of the Atlantic material, and the differences in shape exhibited by their female gonothecae, it seems justifiable to allocate them to a species different from S. rosea, in this case to S. hemisphaerica (Allman, 1888), the latter being the oldest available name.

Distribution in Chile. The present record from Los Gemelos is the first for the country.

World records. Silicularia rosea occurs circumglobally in Antarctic and subantarctic waters (Vervoort & Watson 2003).