Staurotheca frigida Peña Cantero, Svoboda and Vervoort, 1997

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 : 2683-2689

Staurotheca frigida Peña Cantero, Svoboda and Vervoort, 1997

(figure 8)

Staurotheca frigida Peña Cantero, Svoboda and Vervoort, 1997: 350–353 , figure 4; Peña Cantero and García Carrascosa, 1999: 212 et seq.; Peña Cantero et al., 1999: 160.

Staurotheca dichotoma: Jäderholm, 1905: 33 , pl. 14 figures 1, 2.

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.

Material examined. 000 AM, one fragment ca 15 mm long ( USNM 1003164); 22 / 1535, seven fragments up to 20 mm long ( USNM 1003165); 32 / 1995, several fragments up to 10 mm long ( USNM 1003166); 32 / 1996, one fragment ca 11 mm long ( USNM 1003167); 32 / 1997, numerous fragments ( USNM 1003168); 32 / 2095, six fragments up to 15 mm long ( USNM 1003169); 575 / 031, a mass of branches ca 30 mm in diameter, with male and female gonothecae ( USNM 1003170; RMNH- Coel. 30267); 575 / 032, a mass of branches ca 30 mm in diameter, with female gonothecae ( USNM 1003171; RMNH-Coel. 30268); 575 / 033, a mass of branches ca 15 mm in diameter ( USNM 1003172); 575 / 039, three fragments up to 20 mm long, with male gonothecae ( USNM 1003173); 575 / 061, a mass of branches ca 90 mm in diameter ( USNM 1003174; RMNH-Coel. 30269; MNCN 2.03/266); 575 / 070, a mass of branches ca 15 mm in diameter ( USNM 1003175); 575 / 071, one stem ca 5 mm high ( USNM 1003176); 575 / 083, a mass of branches ca 80 mm in diameter, with male and female gonothecae ( USNM 1003177; RMNH-Coel. 30270; MNCN 2.03/267); 575 / 085, a mass of branches ca 60 mm in diameter ( USNM 1003178; RMNH-Coel. 30271); 575 / 088, a mass of branches ca 50 mm in diameter ( USNM 1003179; RMNH-Coel. 30272); 575 / 090, a mass of branches ca 40 mm in diameter ( USNM 1003180; RMNH-Coel. 30273); 575 / 094, a mass of branches ca 40 mm in diameter, with female gonothecae ( USNM 1003181; RMNH-Coel. 30274); 575 / 095, a mass of branches ca 30 mm in diameter, with female gonothecae ( USNM 1003182; RMNH-Coel. 30275); 575 / 097, a mass of branches ca 20 mm in diameter ( USNM 1003183); 575 / 098, a mass of branches ca 50 mm in diameter, with male and female gonothecae ( USNM 1003184; RMNH-Coel. 30276; MNCN 2.03/268); 575 / 101, a mass of branches ca 50 mm in diameter ( USNM 1003185; RMNH-Coel. 30277; MNCN 2.03/269); 601 / 008, a mass of branches ca 30 mm in diameter, with female gonothecae ( USNM 1003186); 601 / 011, a mass of branches and stems ca 60 mm in diameter, with male and female gonothecae ( USNM 1003187; RMNH- Coel. 30278; MNCN 2.03/270); 601 / 012, two masses of branches and stems ca 80 mm in diameter, with male gonothecae ( USNM 1003188; RMNH-Coel. 30279; MNCN 2.03/271); 601 / 013, a mass of branches ca 50 mm in diameter, with female gonothecae ( USNM 1003189; RMNH-Coel. 30280); 601 / 014, two fragments up to 45 mm long, with female gonothecae ( USNM 1003190); 601 / 015, a mass of branches ca 20 mm in diameter, with female gonothecae ( USNM 1003191); 601 / 023, a mass of branches ca 30 mm in diameter, with female gonothecae ( USNM 1003192); 601 / 036, a mass of branches ca 10 mm in diameter, with male gonothecae ( USNM 1003193); 601 / 044, a mass of branches ca 60 mm in diameter, with female gonothecae ( USNM 1003194; RMNH-Coel. 30281; MNCN 2.03/272); 601 / 064, a mass of branches ca 60 mm in diameter, with female gonothecae ( USNM 1003195; RMNH- Coel. 30282); 601 / 065, a mass of branches ca 90 mm in diameter, with male and female gonothecae ( USNM 1003196; RMNH-Coel. 30283; MNCN 2.03/273); 601 / 081, several fragments up to 35 mm long ( USNM 1003197); 601 / 083, a mass of branches ca 50 mm in diameter, with male gonothecae ( USNM 1003198; RMNH- Coel. 30284); 601 / 084, a mass of branches ca 40 mm in diameter ( USNM 1003199); 601 / 122, seven fragments up to 20 mm long ( USNM 1003200); 691 / 020, a mass of stems ca 50 mm in diameter, with male gonothecae ( USNM 1003201; RMNH-Coel. 30285; MNCN 2.03/274); 876 / 111, two fragments up to 15 mm long ( USNM 1003202); 876 / 112, two fragments up to 5 mm long ( USNM 1003203); 876 / 123, a mass of branches ca 80 mm in diameter, with male and female gonothecae ( USNM 1003204; RMNH-Coel. 30286; MNCN 2.03/275); 876 / 124, a mass of branches ca 60 mm in diameter, with male gonothecae ( USNM 1003205; RMNH-Coel. 30287; MNCN 2.03/276); 876 / 125, two masses of branches up to 40 mm in diameter, with male and female gonothecae ( USNM 1003206; RMNH-Coel. 30288).

Description. Colonies composed of a mass of tightly interwoven branches and stems, giving the colony the aspect of a globular network, up to 90 mm in diameter. Branching frequent, irregular and in several planes; with anastomoses.

Hydrothecae arranged in decussate pairs (figure 8A, B), forming four longitudinal rows of hydrothecae. Hydrothecae (figure 8A–F) immersed into the branches for approximately one-third of their volume. Adcauline hydrothecal wall free for oneeighth to one-third of its length. Free adcauline wall approximately straight. Abcauline wall almost straight, though becoming concave distally. Hydrothecal aperture mainly circular and slightly tilted downwards; rim either even and the aperture circular, or uneven, due to the presence of a more or less distinct abcauline elevation.

Male and female gonothecae present. Female gonothecae (figure 8G) as those of S. antarctica and S. compressa . Male gonothecae fusiform, occasionally with a few downwardly directed digitiform processes (figure 8H).

Remarks. Staurotheca frigida was described by Peña Cantero et al. (1997) as having the rim of the hydrothecal aperture either even or uneven, with a slight abcauline elevation and differing from S. cornuta by the presence of a sharp abcauline elevation in that species (cf. Peña Cantero et al., 1999). The study of the USAP material shows that in S. frigida there is considerable variation in the rim of the hydrothecal aperture. It is possible to find, even in the same colony (cf. figure 8C–F), hydrothecae with an even rim, others with a slight abcauline elevation and, finally, hydrothecae with a strong abcauline elevation, similar to that present in the hydrothecae of S. cornuta . In spite of this, S. cornuta is clearly distinguished from S. frigida by the arrangement of the hydrothecae that are always in decussate verticils of three hydrothecae, forming six longitudinal rows, by the constant presence of a strong abcauline elevation of the rim, by the greater robustness of the colony due to the stronger development of perisarc and, finally, by the shape of the female gonothecae, with moderately ornamented gonothecal walls, usually with only one long cusp above the aperture.

Hydrothecae with the rim of the hydrothecal aperture even resemble those of S. antarctica , though in that species the hydrothecae have a longer free adcauline wall. Alternatively, hydrothecae of S. frigida with an abcauline elevation approach those of S. compressa , but in that species the uneven rim, which is laterally depressed, is due to the presence of both one abcauline and one adcauline elevation of the rim, whereas in S. frigida the lateral depression is due only to the development of the abcauline process.

Ecology and distribution. Staurotheca frigida is a shelf species (Peña Cantero et al., 1997) having been found from 86 (Peña Cantero and García Carrascosa, 1994) to 330 m (Peña Cantero et al., 1997). We found it from depths of 57– 550 m. It has been collected on muddy bottoms (Peña Cantero et al., 1997), muddy and sandy bottoms (Jäderholm, 1905), and stony and rocky bottoms (Peña Cantero and García Carrascosa, 1994). Staurotheca frigida has also been reported growing epibiotic on hydroids (Peña Cantero and García Carrasosa, 1994) and on non-calcified bryozoans (Peña Cantero et al., 1997). We also found it epibiotic on bryozoans. It is used in turn as a substratum by other hydroids ( Antarctoscyphus sp. , Halecium sp. , Lafoea sp. , Sertularella sp. , Symplectoscyphus sp. ). It has been found with gonothecae in January and March (Peña Cantero et al., 1997), April (Millard, 1977) and December (Peña Cantero and García Carrascosa, 1994). In our material fertile colonies were collected in February, May, June, November and December. It therefore seems fertile throughout the year, except during the winter.

Staurotheca frigida has an Antarctic–Kerguélen distribution. It had been reported from off South Georgia (Jäderholm, 1905; Peña Cantero and García Carrascosa, 1994), Clerke Rocks, South Shetland and South Orkney Islands (Peña Cantero and García Carrascosa, 1994), east coast of the Weddell Sea (Peña Cantero et al., 1997) and off the Crozet Islands (Millard, 1977; Peña Cantero et al., 1997). In our material, it was found off the Antarctic Peninsula and at the Scotia Ridge islands, in the Ross Sea area and off the Wilkes Land region. In the Scotia Ridge, S. frigida was found from off Candlemas and Visokoi islands ( South Sandwich Islands), off Coronation and Laurie islands (South Orkney Islands), and off South Georgia and Shag Rocks; at the Antarctic Peninsula it was found west of Renaud Island (Biscoe Islands). In the Ross Sea, S. frigida was found in the central basin and east of Cape Hallett (Victoria Land). Finally, it was obtained north of Wilkes Station, Budd Coast, Wilkes Land.

Staurotheca glomulosa Peña Cantero, Svoboda and Vervoort, 1997 (figure 9)

Staurotheca glomulosa Peña Cantero et al., 1997: 353–356 , figures 5, 13B; 1999: 160; Peña Cantero and García Carrascosa, 1999: 215.

Material examined. 000AG, several fragments up to 30 mm long ( USNM 1003207); 000 AM, a few fragments up to 50 mm long ( USNM 1003208); 27 / 1952, a mass of branches ca 60 mm in diameter, with female gonothecae ( USNM 1003209; RMNH-Coel. 30289; MNCN 2.03/277); 32 / 1995, numerous fragments up to 22 mm long ( USNM 1003210; RMNH-Coel. 30290); 32 / 2005, numerous fragments up to 35 mm long ( USNM 1003211; RMNH-Coel. 30291); 32 / 2083, a mass of branches ca 30 mm in diameter, with female gonothecae ( USNM 1003212; RMNH-Coel. 30292); 32 / 2095, a mass ca 30 mm in diameter ( USNM 1003213; RMNH-Coel. 30293); 5 / 291, nine fragments up to 30 mm long ( USNM 1003214); 575 / 020, three fragments up to 13 mm long ( USNM 1003215); 575 / 031, a few fragments up to 45 mm long ( USNM 1003216); 575 / 033, a few fragments up to 23 mm long ( USNM 1003217); 575 / 061, two fragments up to 30 mm long ( USNM 1003218); 575 / 085, a few fragments up to 50 mm long ( USNM 1003219); 575 / 094, a few fragments up to 35 mm long ( USNM 1003220); 575 / 097, three fragments up to 40 mm long ( USNM 1003221); 575 / 101, a mass of fragments up to 30 mm in diameter (fragments up to 50 mm long) ( USNM 1003222; RMNH-Coel. 30294; MNCN 2.03/278); 6 / 410, numerous fragments up to 20 mm long, with male gonothecae ( USNM 1003223); 6 / 441, several fragments interwoven with those of Staurotheca compressa and a mass of stems ca 10 mm in diameter ( USNM 1003224); 601 / 044, a mass ca 20 mm in diameter ( USNM 1003225; RMNH-Coel. 30295); 721 / 5435, a mass of branches ca 50 mm in diameter, with male gonothecae ( USNM 1003226; RMNH-Coel. 30296; MNCN 2.03/279); 721 / 765, a few fragments up to 40 mm long ( USNM 1003227); 766, one stem ca 50 mm high ( USNM 1003228); 767, several fragments up to 70 mm long ( USNM 1003229); 768, a mass of branches ca 50 mm in diameter, with female gonothecae ( USNM 1003230; RMNH-Coel. 30297; MNCN 2.03/280); 824 / 013-1, numerous fragments up to 35 mm long, with female gonothecae ( USNM 1003231); 876 / 123, a mass of branches ca 30 mm in diameter, with male gonothecae ( USNM 1003232; RMNH-Coel. 30298; MNCN 2.03/281); 876 / 124, a mass of branches ca 20 mm in diameter, with male gonothecae ( USNM 1003233; RMNH-Coel. 30299).

Description. Colonies composed of masses of interwoven, usually polysiphonic stems and branches with anastomoses, up to 60 mm in diameter.

Hydrothecae present along whole length of colony, arranged in decussate pairs (figure 9A) forming four longitudinal rows. Hydrothecae (figure 9A–D) immersed into branches for approximately one-third of volume. Free adcauline wall of hydrotheca one-sixth to one-tenth of its total length, straight. Abcauline wall slightly convex basally, but becoming concave distally. Hydrothecal aperture circular; rim even and usually with numerous renovations.

Male and female gonothecae present. Female gonothecae typically set in a glomulus formed by a series of stolonal tubes from which the individual gonothecae arise. Stolons also provided with isolated hydrothecae arranged in an irregular pattern; hydrothecae of glomulus smaller and with a larger part of the adcauline wall free (figure 9E, F). Gonotheca urn-shaped (figure 9G), with a globular basal part narrowing into a large distal neck provided with a wide distal aperture. Gonothecal wall with striae at base of neck. Female gonothecae also inserting individually at hydrothecal base. Male gonothecae not aggregated in a glomulus but arising directly at hydrothecal base. Male gonotheca fusiform (figure 9H), provided with a small and circular aperture at the end of a short conical neck.

Remarks. Although Peña Cantero et al. (1997) characterized this species by the female gonothecae set in a glomulus, the newly examined material provides evidence that the female gonothecae are not always grouped in that structure, as in several female colonies, clearly belonging to this species, the gonothecae are individually inserted at the hydrothecal base while there are no remnants of a glomulus or of a stolon.

As intimated by Peña Cantero et al. (1997), S. glomulosa is allied to S. dichotoma in shape of hydrothecae and gonothecae. In S. dichotoma , however, the hydrotheca has a distinctly larger diameter at the aperture, the abcauline hydrothecal wall is straight basally and the gonothecae are never found in a glomulus. Moreover, colonies of S. glomulosa are strongly polysiphonic, whereas those of S. dichotoma are usually monosiphonic.

Ecology and distribution. Staurotheca glomulosa is a shelf species. It had been recorded from depths of 200–672 m on muddy bottoms (Peña Cantero et al., 1997). We found it from 55 to 870 m, growing on gravel. It is used as substratum by species of Hebella . Colonies with gonothecae were collected from January to March (Peña Cantero et al., 1997). In our material, fertile colonies were found in February, March and December. It seems to be fertile during the southern summer.

Staurotheca glomulosa was previously known only from the southern and eastern parts of the Weddell Sea and off Elephant Island (Peña Cantero et al., 1997). In our material it occurs in collections from the Ross Sea and the Victoria Land area, Wilkes Land region and from off the Antarctic Peninsula and Scotia Ridge islands. In the Ross Sea and Victoria Land area, S. glomulosa was found in the central basin, at Pennell Bank, east of Cape Hallett and off Buckle Island (Balleny Islands). Off Wilkes Land it was found north of Wilkes Station (Budd Coast). Finally, at the Antarctic Peninsula and Scotia Ridge islands it was collected from off Anvers Island (Palmer Archipelago), Argentine Island and Low Island, in the Antarctic Peninsula area, and off Visokoi Island (South Sandwinch Islands), south of Laurie Island (South Orkney Islands) and South Georgia, in the Scotia Ridge region.