Staurotheca vervoorti (El Beshbeeshy, 1991)

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 : 2710-2712

Staurotheca vervoorti (El Beshbeeshy, 1991)

(figure 19)

Thuiaria vervoorti El Beshbeeshy, 1991: 250–253 , figure 64.

Sertularella edentula: Vervoort, 1972: 127 , figure 39b–d; Blanco, 1994a: 154; 1994b: 199. Thuiaria edentula : Stepan’yants, 1979: 92, pl. 17 figure 9A–V.

Staurotheca vervoorti: Peña Cantero et al., 1997: 337 ; 1999: 160.

Material examined. 22 / 1592, three stem fragments up to 150 mm long, with gonothecae ( USNM 1003292; RMNH-Coel. 30328); 6 / 377, one fragmented colony (fragments up to 70 mm long) ( USNM 1003293; RMNH-Coel. 30329; MNCN 2.03/298); 7 / 551, one stem ca 65 mm high ( USNM 1003294); 9 / 724, one stem ca 100 mm high ( USNM 1003295).

Description. Stems up to 150 mm long, polysiphonic over a great extension. Branching dichotomous and in one plane. Branches strongly contracted at their base and originating at a position corresponding to a hydrotheca. Both stems and branches flattened.

Hydrothecae arranged in subopposite or alternate pairs, forming two longitudinal series (figure 19A, B). In these series, hydrothecae may be closely approximated.

Hydrothecae cylindrical and almost straight (figure 19A–E); usually adnate to stem for their entire adcauline length (figure 19B, C, E). In the material from Stn 22/1592 and Stn 6/377 the free adcauline hydrothecal wall is inconspicuous (figure 19A, D). Abcauline hydrothecal wall straight or slightly concave. Aperture circular, tilted downwards and forming an acute angle with the long axis of branch, provided with a dish-shaped operculum. Rim even or uneven and slightly laterally depressed, sometimes with a few short renovations. Hydrotheca without mushroomshaped diaphragm.

Presumed male gonothecae usually developing inside the hydrothecae (figure 19E), though also originating from their base (figure 19F). Gonotheca fusiform with a small circular aperture on an inconspicuous distal neck (figure 19E, F).

Cnidome composed of microbasic mastigophores in two size groups: a larger (19.6–21.7×4.2–4.9 Mm) and a smaller group (7–7.7×2.8–3.5 Mm).

Remarks. El Beshbeeshy (1991) described gonothecae of this species from his Patagonian material. These ‘gonothecae’ may actually represent mollusc eggs deposited on the branches of S. vervoorti .

Ecology and distribution. Staurotheca vervoorti had been found at depths from 310 (El Beshbeeshy, 1991) to 1500 m (Stepan’yants, 1979). We found it from 1647 to 2727 m. In our material fertile colonies were collected in March.

Staurotheca vervoorti is a Patagonian species. It had been reported from off the Patagonian coasts (Stepan’yants, 1979; El Beshbeeshy, 1991) and south-east of the Falkland Islands (Vervoort, 1972). Our material comes from Burdwood Bank and off South Georgia.