Hydractinia angusta Hartlaub, 1904

Galea, Horia R. & Schories, Dirk, 2012, Some hydrozoans (Cnidaria) from King George Island, Antarctica, Zootaxa 3321, pp. 1-21 : 2

Hydractinia angusta Hartlaub, 1904

(Pl. 1A–E, Fig. 2A–C )

Hydractinia angusta Hartlaub, 1904: 7 , pl. 4. — Naumov & Stepanjants, 1972: 35, fig. 1. — Stepanjants, 1979: 13, pl. 1 fig. 7. — Peña Cantero & Ramil, 2006: 950, fig. 2A. — Peña Cantero, 2012: 855.

Hydronema angustum — Stechow, 1923: 67. — Totton, 1930: 138. — Briggs, 1939: 10.

Hydractinia dendritica Hickson & Gravely, 1907: 9 , pl. 2 figs 7–10.

Hydronema dendriticum — Stechow, 1921: 252. — Stechow, 1923: 67, fig. F.

? Hydractinia sp. —Stepanjants, 1972: 59, fig. 4.

Material examined. Stn. SHO — 16.ii.2011, Ant.09/2011 (43 m): fertile (female) colony on worm tube (MHNG- INVE-79798). Stn. ARD — 28.i.2011, Ant.11/2011 (39 m): fertile (female) colony on worm tube (MHNG-INVE- 79799).

Description. Hydrorhiza an encrusting mat issued through the coalescence of the stolonal system, covered by naked coenosarc (Pl. 1C). Spines present, often continuous with each other (Pl. 1D), provided with low ridges of perisarc (Pl. 1E), open or closed at tips. Polyps dimorphic: gastro- and gonozooids. Gastrozooids up to 5 mm high in fixed material, notably longer in life (Pl. 1A); with 12–14 amphicoronate tentacles and dome-shaped hypostome. Gonozooids dwarfed, less than 0.5 mm high, and degenerate, with 1–5 tentacles, and possibly no mouth; 4–6 rounded gonophores basally, each carrying three eggs. Nematocysts: desmonemes (6.0–6.5) × (3.6–3.8) µm and microbasic euryteles (8.9–9.8) × (3.1–3.5) µm (both measured undischarged).

Remarks. Totton (1930) reexamined the type of H. dendritica Hickson & Gravely, 1907 and suggested that it could reasonably be considered as conspecific with Hartlaub's (1904) species, an opinion which is followed here.

Geographical distribution. Circum-Antarctic ( Peña Cantero & Ramil 2006).

Figures

FIGURE 2. A – C: Hydractinia angusta Hartlaub, 1904 — fragment of colony showing gastro-, gonozooid, and spine (A); gonozooid (B); cnidome (C). D: Opercularella sp. — hydrothecate pedicel. E, H: Halecium antarcticum Vanhöffen, 1910 — stem internode (E); gonotheca (H). F, G, I: Halecium delicatulum Coughtrey, 1876 — specimen MHNG-INVE- 26669, showing hydrothecae (F), stem internodes (G), and a female gonotheca (I). J, K: Halecium ovatum Totton, 1930 — fragment of stem showing branching pattern (J); female fonotheca (K). L, M: Antarctoscyphus elongatus (Jäderholm, 1904) — internodes with hydrothecae (L); gonotheca (M). N – P: Antarctoscyphus spiralis (Hickson & Gravely, 1907) — internode with hydrotheca (N); hydrothecal aperture in frontal view, showing intrathecal cusps (O); gonotheca (P). Q – S: Sertularella gaudichaudi (Lamouroux, 1824) — fragment of stem (Q); hydrotheca (R); female gonotheca (S). T, U: Symplectoscyphus cumberlandicus (Jäderholm, 1905) — fragment of stem (T); female gonotheca (U). V, W: Symplectoscyphus glacialis (Jäderholm, 1904) — fragment of stem (V); gonotheca (W). X – Z: Symplectoscyphus vanhoeffeni Totton, 1930 — fragments of stems from Stn. Ant. 06 / 2011 (X) and Stn. Ant. 12 / 2010 (Y); gonotheca from material from Stn. Ant. 06 / 2011 (Z). Scale bars: 10 µm (C), 100 µm (O), 300 µm (D, R), 400 µm (B), 500 µm (E – I, K – N, P, V – Z), 800 µm (J), 900 µm (T), 1 mm (A, Q, S, U).