Staurotheca vanhoeffeni

Staurotheca vanhoeffeni (Peña Cantero and García Carrascosa, 1994)

(figure 18)

Dictyocladium affine: Vanhöffen, 1910: 331, figure 44a–c.

Thuiaria affinis: Stepan’yants, 1979: 95, pl. 18 figure 1, pl. 24 figures D, E, I.

Selaginopsis vanhöeffeni Peña Cantero, 1991: 83–86, pls 9, 43, pl. 65 figure a.

Selaginopsis vanhoeffeni Peña Cantero and García Carrascosa, 1994: 121, figure 3j–n; 1995: 32–35, figures 9A–J, 10A–E, 61D; Peña Cantero et al., 1996: 1–10, figures 1–3.

Staurotheca vanhoeffeni: Peña Cantero et al., 1997: 337, 373–375, figure 12; 1999: 160; Peña Cantero and García Carrascosa, 1999: 212 et seq.

Material examined. 12 / 1002, one extremely fragmented stem (largest fragment ca 90 mm long), with female gonothecae (USNM 1003287; RMNH-Coel. 30325; MNCN 2.03/296); 12 / 1003, numerous fragments up to 60 mm long (USNM 1003288; RMNH-Coel. 30326); 32 / 1995, two fragments up to 7 mm long (USNM 1003289); 46 / 5042, several fragments and stems up to 85 mm high, with male gonothecae (USNM 1003290; RMNH-Coel. 30327; MNCN 2.03/297); 6 / 418, four fragments up to 18 mm long (USNM 1003291).

Description. Material in fragmentary state, largest fragment up to 60 mm long, with polysiphonic stem and branches. Branching in one plane, alternate or irregular; with anastomoses.

Hydrothecae arranged in decussate verticils of three to four hydrothecae (figure 18A) forming six to eight longitudinal rows. Hydrothecae (figure 18A–F) immersed into the stem and branches for approximately half their volume and adnate for almost full adcauline length. In lateral view hydrotheca cylindrical and slightly curved outwards. In frontal view maximum hydrothecal diameter at the hydrothecal base, from where diameter smoothly decreasing towards the aperture. Abcauline hydrothecal wall slightly concave. Hydrothecal aperture circular and tilted downwards, forming an acute angle with long axis of stem. Rim of hydrotheca even, frequently with a few, short renovations. Diaphragm mushroom-shaped, with two abcauline projections pointing towards the hydrothecal lumen.

Both male and female gonothecae present, originating at the hydrothecal base. Proximal part of female gonotheca (figure 18G) cone-shaped, distally with a wide neck bearing a strongly laterally depressed aperture due to the presence of two lips of approximately equal development. Male gonotheca fusiform (figure 18H), provided with a distal neck bearing a small, circular aperture.

Ecology and distribution. Staurotheca vanhoeffeni is a shelf species (Peña Cantero et al., 1997), having been found from depths between 100 (Stepan’yants, 1979) and 400 m (Peña Cantero and García Carrascosa, 1994) on bottoms of pebbles (Vanhöffen, 1910; Peña Cantero and García Carrascosa, 1994) and stones (Peña Cantero et al., 1997). We found it from 210 to 426 m on gravel. Fertile colonies were collected in January (Peña Cantero and García Carrascosa, 1994), February and March (Peña Cantero et al., 1997) and April (Vanhöffen, 1910; Stepan’yants, 1979); in our material colonies collected in January and March have gonothecae.

Staurotheca vanhoeffeni has a circum-Antarctic distribution (Peña Cantero and García Carrascosa, 1994), being known from both East and West Antarctica. In the former it is known from the Davis Sea (Vanhöffen, 1910; Stepan’yants, 1979). In West Antarctica, S. vanhoeffeni has been reported from off Graham Land (Stepan’yants, 1979), the South Shetland Islands (Stepan’yants, 1979; Peña Cantero and García Carrascosa, 1994), Elephant Island (Peña Cantero and García Carrascosa, 1994) and the eastern part of the Weddell Sea (Peña Cantero et al., 1997). It is also known from off Heard Island (Stepan’yants, 1979) at the limits of the Antarctic region. Our material comes from the region of the Antarctic Peninsula (off Elephant Island, north-east of Joinville Island and north of d’Urville Island), from east of Cape Hallett (Victoria Land), from the Ross Sea, and from west of Heard Island.