Silicularia rosea Meyen, 1834

Galea, Horia R., Häussermann, Verena & Försterra, Günter, 2009, New additions to the hydroids (Cnidaria: Hydrozoa) from the fjords region of southern Chile, Zootaxa 2019, pp. 1-28 : 18-19

Silicularia rosea Meyen, 1834

(fig. 4G–M, table 6)

Silicularia rosea Meyen, 1834: 204 , pl. 35 figs 1–11. – Hartlaub, 1905: 572, figs V1, X1, Y 1. – Vervoort & Watson, 2003: 442, fig. 108A–D.

? Campanularia bilabiata Coughtrey, 1875: 291 , pl. 20 figs 46–49.

? Hypanthea bilabiata – Hilgendorf, 1898: 213, pl. 20 figs 5, 5A.

Silicularia bilabiata – Bale, 1924: 233, fig. 4. – Ralph, 1956: 285, fig. 2A, C. – Naumov & Stepanjants, 1962: 73, fig. 2.

Silicularia bilabiata forma intermedia – Ralph, 1956: 286, figs 2F, 3A–D.

Silicularia bilabiata forma subantarctica – Ralph, 1956: 287, fig. 3K.

Silicularia bilabiata forma subtropica – Ralph, 1956: 286, figs 2D, 3E–J.

Eucopella campanularia p.p. von Lendenfeld, 1883: 497, pl. 29 fig. 15D', D1/2. – Bale, 1888: 751, pl. 13 figs 9–15.

Silicularia campanularia – Bale, 1914: 84, pl. 13 figs 1–6. – Hodgson, 1950: 6, figs 12–13.

Hypanthea aggregata Allman, 1888: 27 , pl. 14 figs 1, 1A.

Hypanthea repens Allman, 1876: 115 .

Hypanthea hemisphaerica Allman, 1888: 27 , pl. 14 figs 2, 2A.

Silicularia hemisphaerica – Hartlaub, 1905: 576, figs Z1, A2. – Jäderholm, 1905: 18, pl. 7 fig. 3.

Hypanthea atlantica Marktanner-Turneretscher, 1890: 211 , pl. 3 fig. 14.

Hypanthea asymmetrica Hilgendorf, 1898: 212 , pl. 20 fig. 4. – Hartlaub, 1901b: 366, pl. 22 figs 24–26.

Eucopella reticulata Hartlaub, 1905: 569 , fig. R1.

Silicularia reticulata – Nutting, 1915: 91, pl. 25 figs 3–4.

Material examined. Stn. 10 – 24.02.2008, 8 m, A504 ( MHNG INVE 62833): numerous hydrothecae and several female gonothecae, on weeds.

Type locality. Not designated by Meyen (1834). For a list of his records, see Vervoort & Watson 2003.

Description. Colony stolonal, with polyps arising at irregular intervals from branched, anastomozing, thick-walled stolon. Hydrothecal pedicels of moderate length, slightly constricted at origin from stolon; perisarc very thick, entirely smooth; subhydrothecal spherule present. Hydrotheca long, inverted-conical, asymmetrical, walls straight to slightly undulated or curved; oval in cross-section (bilaterally symmetrical), with perisarc much thickened laterally in frontal view, and lesser on front and rear sides (fig. 4I); perisarc exceptionally thickened towards base of hydrotheca, delimiting an ovoid to nearly tubular basal chamber of varied height; aperture perpendicular to long axis of hydrotheca; rim even, not everted. Only remnants of hydranths present; tentacle number could not be checked. Gonothecae borne on stolon; female in present material, immature; pear-shaped, laterally compressed, with thickened, slightly undulated lateral walls; distal end truncated to broadly rounded, with wide, operculate aperture; proximal end tapering abruptly into short, smooth pedicel. Gonothecal content badly preserved; one central, large medusoid and a smaller, basal one, the latter often disintegrated in majority of gonothecae examined and fine structure could not be observed. Nematocysts (undischarged): large capsules (9.4–10.8) × (2.8–3.1) µm; small capsules ca. 5.6 × 1.4 µm.

Remarks. The position of hydrothecal aperture in the present material is rather peculiar, and is similar to that observed by Coughtrey (1875) in his Campanularia bilabiata . Nearly all the variants of Silicularia rosea ( Meyen, 1834) described in the literature have the aperture obviously inclined to one side (see references above). The peculiar feature observed by us probably occurs only seldomly, but still belongs to the normal range of variation found in this species. Additionally, the long hydrothecae belong to Ralph’s (1956) forma subantarctica .

On the other hand, the female gonothecae are immature in the present material, with the characteristic, distal part not formed yet. Comparison of the Chilean specimens with female colonies from Tristan da Cunha (South Atlantic), bearing both mature and immature gonothecae (Galea, unpublished results), leave no doubt about the earliness of their development. Immature female gonothecae, with similar morphology, were illustrated by both Ralph (1956) (p. 292, fig. 3I) and Blanco (1967a) (p. 224, fig. 5) for specimens originating from New Zealand and Argentina, respectively.

Nevertheless, additional studies on Chilean material are necessary to evaluate the intraspecific variation modulated by both genetic and ecological factors, as well as the examination of the morphology of male colonies.

World distribution. Circumglobal in Antarctic and subantarctic waters ( Vervoort & Watson 2003). Records from Chile. Strait of Magellan ( Jäderholm 1903, as H. repens ), Navarino Island ( Hartlaub 1905, as S. hemisphaerica ), South of Chiloé Island (present study).

– pedicel diameter 130–180 – – – –