Staurotheca antarctica Hartlaub, 1904

Cantero, A. L. Peña & Vervoort, W., 2003, Species of Staurotheca Allman, 1888 (Cnidaria: Hydrozoa: Sertulariidae) from US Antarctic expeditions, with the description of three new species, Journal of Natural History 37 (22), pp. 2653-2722 : 2670-2673

Staurotheca antarctica Hartlaub, 1904

(figure 3)

Staurotheca antarctica Hartlaub, 1904: 16 , pl. 1 figure 4, pl. 2 figure 4; 1905: 616; Vanhöffen, 1910: 329, figure 43a–c; Billard, 1906: 3; 1914: 13, figures 7, 8; Stechow, 1919: 82; Ushakov, 1964: 289; Blanco, 1971: 64; 1978: 157, figure 3; 1992: 155, figure 1; 1994a: 160; 1994b: 196; Bouillon et al., 1995: 76; Peña Cantero et al., 1997: 336, 340–345, figure 1; 1999: 160.

? Staurotheca reticulata Ritchie, 1907: 538 , pl. 1 figure 1a, b; Billard, 1914: 16; Rees and Thursfield, 1965: 115, 200; Smaldon et al., 1976: 18.

? Staurotheca antarctica: Totton, 1930: 177 , figure 28, pl. 2 figure 6; Briggs, 1938: 26; Naumov and Stepan’yants, 1972: 34, 51; Stepan’yants, 1972: 71; 1979: 98, pl. 19 figure 1.

Not Staurotheca antarctica: Millard, 1977: 21 ; Peña Cantero, 1991: 113, pl. 17; Peña Cantero and García Carrascosa, 1994: 122, figure 5e, f; 1995: 59–62, figure 25A–E (= Staurotheca frigida Peña Cantero, Svoboda and Vervoort, 1997 ).

Not Staurotheca antarctica: Naumov and Stepan’yants, 1962: 90; Vervoort, 1972: 198, figures 67, 68b (=? Staurotheca nonscripta Peña Cantero, Svoboda and Vervoort, 1997 ).

Material examined. 00DAB, two fragments up to 6 mm long (USNM 1003108); 27 / 1896, several fragments up to 17 mm long (USNM 1003109); 32 / 1995, several fragments up to 7 mm long (USNM 1003110); 32 / 2021, one fragment ca 8 mm long (USNM 1003111); 32 / 2072, numerous small fragments (USNM 1003112; RMNH- Coel. 30241); 32 / 2080, a mass of branches ca 20 mm in diameter, with female gonothecae (USNM 1003113; RMNH-Coel. 30242; MNCN 2.03/250); 32 / 2082, a mass of branches ca 15 mm in diameter, with male gonothecae (USNM 1003114); 32 / 2095, seven fragments up to 10 mm long (USNM 1003115); 51 / 5762, one fragment ca 11 mm long (USNM 1003116); 721 / 765, a mass of branches ca 20 mm in diameter (USNM 1003117; RMNH-Coel. 30243; MNCN 2.03/251); 721 / 843, two fragments up to 20 mm long (USNM 1003118); 731 / 1843, a mass of branches ca 25 mm in diameter, with male gonothecae (USNM 1003119; RMNH-Coel. 30244; MNCN 2.03/252); 731 / 1861, a mass of branches ca 10 mm in diameter (USNM 1003120; RMNH-Coel. 30245); 824 / 041-1, a mass of branches ca 30 mm in diameter (USNM 1003121; RMNH-Coel. 30246; MNCN 2.03/253); B-23NOV, three fragments up to 10 mm long, in bad condition, with gonothecae (USNM 1003122); SOSC-L26, three fragments up to 22 mm long (USNM 1003123).

Description. Colonies consisting of a mass of stems and branches up to 30 mm in diameter. Branching frequent and irregular. Branches numerous and provided with many anastomoses, giving the colony a compact appearance.

Hydrothecae arranged in decussate pairs, forming four longitudinal rows (figure 3A, B). Hydrotheca small (figure 3A–E), with a small part immersed into the branch. Hydrotheca cylindrical, but distinctly curved outwards (figure 3A–C, E). Adcauline hydrothecal wall adnate to internode for ca half or two-thirds of its length. Free adcauline wall straight or slightly convex. Abcauline hydrothecal wall concave. Hydrothecal aperture circular. Some hydrothecae with renovations of the hydrothecal rim. Hydrothecal diaphragm mushroom-shaped, provided with two abcauline projections pointing into the hydrothecal lumen.

Female and male gonothecae present. Female gonothecae (figure 3D) inserted on a characteristic digitiform, bifid process originating at the hydrothecal base. Gonotheca globular, provided with a large circular aperture facing the bifid process; external wall ornamented by digitiform projections. Male gonothecae inserted directly at the hydrothecal base, fusiform and provided with a small, circular, distal aperture (figure 3E).

Remarks. Staurotheca antarctica belongs to a group of Antarctic species ( S. abyssalis sp. nov., S. compressa , S. cornuta , S. frigida ) characterized by the female gonothecae resting on a digitiform process and having an ornamented external wall, and the small size of the larger microbasic mastigophores (<19 Mm) (cf. table 6).

Peña Cantero et al. (1997), after examining the type series, clarified the status of this species and now it may be considered a well-characterized species, being clearly distinguishable from the other species of the group by the long free part of the hydrotheca and the even rim of the hydrothecal aperture.

Ecology and distribution. Staurotheca antarctica is a shelf species that has been found from 176 (Billard, 1914) to 661 m depth (Peña Cantero et al., 1997) on muddy (Totton, 1930; Peña Cantero et al., 1997), and stony and rocky bottoms (Peña Cantero et al., 1997). The present material comes from 55 to 630 m depth. It has been found with gonothecae in January (Vanhöffen, 1910; Totton, 1930; Peña Cantero et al., 1997) and February (Peña Cantero et al., 1997). In our material fertile colonies were collected in January, February and November. It may be used as substratum by other hydroids ( Hebella sp. , Symplectoscyphus sp. ).

Staurotheca antarctica seems to have a circum-Antarctic distribution, being known from both East and West Antarctica: in the former it has been recorded from Posadowsky Bay, in the Davis Sea (Vanhöffen, 1910) and McMurdo Sound, in the Ross Sea (Totton, 1930); in West Antarctica it is known from the Bellingshausen Sea (70°23∞S, 82°47∞W) (Hartlaub, 1904), Marguerite Bay (Antarctic Peninsula) (Billard, 1914), Petermann Island (65°10∞S, 64°10∞W) (Blanco, 1978), South Georgia (Blanco, 1992, 1994b), and the south and east coasts of the Weddell Sea (Peña Cantero et al., 1997). Our material comes from the Antarctic Peninsula area, the Ross Sea, and the Wilkes Land region. In the Antarctic Peninsula it was found off Anvers Island (Palmer Archipelago), west of Adelaide Island and south of Lavoisier Island (Biscoe Islands). In the Ross Sea region it was found in the central area, off Victoria Land (Franklin Island, east of Cape Hallett, and Pennell Bank) and off Marie Byrd Land (NW of Cape Colbeck). At Wilkes Land, finally, S. antarctica was collected off Wilkes Station at the Budd Coast.