Sertularella robusta Coughtrey, 1876

Galea, Horia R., 2007, Hydroids and hydromedusae (Cnidaria: Hydrozoa) from the fjords region of southern Chile, Zootaxa 1597 (1), pp. 1-116 : 66

Sertularella robusta Coughtrey, 1876

(fig. 15E–I, tables 24, 25)

Sertularella robusta Coughtrey, 1876a: 300 ; Totton, 1930: 195; Ralph, 1961a: 824, fig. 22A–D; Vervoort, 1972a: 129, figs 40, 41A; Leloup, 1974: 33, fig. 27; Blanco, 1976: 42, pl. 4 figs 1–3; Vervoort & Vasseur, 1977: 40, figs 18–22; García-Corrales et al., 1980: 43, fig. 14; Hirohito, 1983: 46, fig. 19; El Beshbeeshy, 1991: 182, fig. 46; Vervoort, 1993: 264; Hirohito, 1995 (English text): 200, fig. 65E–F; Vervoort & Watson, 2003: 172, figs 39F, 40A–F.

Sertularella microtheca Leloup, 1974: 30 , fig. 24.

? Sertularella sp. 3 Naumov & Stepanjants, 1962: 88, fig. 11.

Material examined. Stn. MEL 01 —08.iii.2005, 10– 15 m, S76: a small, sterile colony, creeping on Sertularella argentinica ; S23: one sterile, erect stem, 1.2 cm high ( MHNG INVE 53177). Stn. CCA — 12.iii. 2006, 28 m, S87: a small, sterile colony, epizoic on Lafoea dumosa . Stn. AIN — 11.iii. 2006, 25 m, S111: stolonal colony, epizoic on Synthecium robustum ( MHNG INVE 53361). Stn. ICA — 13.iii. 2006, 12 m, S146: stolonal, sterile colony, epizoic on Symplectoscyphus subdichotomus . Stn. CCO — 09.iii. 2006, 18 m, S144: one fertile colony, epizoic on Symplectoscyphus sp. Stn. CPA — 09.iii. 2005, 15 m, S170: numerous fertile colonies, epizoic on Symplectoscyphus subdichotomus ( MHNG INVE 53503). Stn. CPI — 07.iii. 2006, 24 m, S121: one sterile, stolonal colony, epizoic on Symplectoscyphus subdichotomus .

Type locality. Foveaux Strait oyster bank, New Zealand .

Remarks. For a complete description of this species, see Vervoort & Vasseur (1977). A more recent description is found in Vervoort & Watson (2003), based on New Zealand material.

I have followed El Beshbeeshy’s (1991) opinion by referring Sertularella microtheca Leloup, 1974 to the synonymy of S. robusta Coughtrey, 1876 , due to morphological similarities and dimensions of hydrothecae. Note that the only small gonotheca observed by Leloup (1974) was probably a young gonotheca; it had six distinct transverse annulations and four small projections of perisarc around the aperture, which is a characteristic of the gonotheca of S. robusta . Comparison of measurements between Leloup’s (1974) material and the present specimens is given in table 25.

The present material from Chile is composed either of exclusively stolonal colonies or small, erect stems bearing up to 16 hydrothecae, or a combination of the two. The three characteristic plate-shaped, internal projections of perisarc below the hydrothecal aperture (one abcauline and two laterals) are an omnipresent trait in all specimens.

The number of external transverse rings on hydrothecae is quite variable in this species. In New Zealand material, Ralph (1961a) found specimens with 3–4 complete annulations, while Vervoort & Watson (2003) observed 5–7 rings. Three to four rings were observed as well by Hirohito (1995) in Japanese material. Vervoort & Vasseur (1977) reported 5–6 rings in their material from French Polynesia. Hydrothecae of Chilean material are usually provided with 4–6 well-defined rings.

The gonothecae of S. robusta have a variable number of transverse ribs: 5–8 in the present material, 3–4 in Ralph’s (1961a) material, 4–5 in Vervoort & Watson’s (2003) material, and about eight in Vervoort & Vasseur’s (1977) material.

Some of the gonothecae in the Chilean material contain eggs, and others bear external acrocysts with about 10 developing embryos.

Distribution. Nearly cosmopolitan, being recorded from southeastern and western Pacific, New Zealand, Australia, Indonesia, Japan ( Vervoort & Watson 2003), Tierra del Fuego ( Leloup 1974), French Polynesia ( Vervoort & Vasseur 1977).

Records from Chile. Leloup’s (1974) Sertularella microtheca was collected from Canal Calbuco in the Golfo de Ancud; his material identified as S. robusta was also found in the Golfo de Ancud. The present material was collected between 43°50' S and 50°50' S.