Staurotheca nonscripta 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 : 2696-2698

Staurotheca nonscripta Peña Cantero, Svoboda and Vervoort, 1997

(figure 13)

Staurotheca nonscripta Peña Cantero et al., 1997: 360–362 , figure 7; 1999: 160.

? Staurotheca antarctica: Naumov and Stepan’yants, 1962: 90; Vervoort, 1972: 198, figures 67, 68b.

? Staurotheca dichotoma p.p. Totton, 1930: 178, figure 27a, c.

Material examined. 27 / 1877, a mass of branches ca 90 mm in diameter, with male and female gonothecae (USNM 1003253; RMNH-Coel. 30311; MNCN 2.03/289); 27 / 1885, a mass of branches ca 30 mm in diameter, with male gonothecae (USNM 1003254); 32 / 2068, a mass of stems ca 70 mm in diameter, with male and female gonothecae (USNM 1003255; RMNH-Coel. 30312; MNCN 2.03/290); 32 / 2080, four fragments up to 10 mm long (USNM 1003256); 32 / 2125, a mass of stems ca 40 mm in diameter, with female gonothecae (USNM 1003257; RMNH- Coel. 30313); 693 / NONE 2, one fragment ca 4 mm long (USNM 1003258); EAD- 3, a mass of branches ca 70 mm in diameter (USNM 1003259; RMNH-Coel. 30314); GLD-12, one fragment ca 11 mm long (USNM 1003260); GLD-13, a mass ca 50 mm in diameter, with female gonothecae (USNM 1003261; RMNH-Coel. 30315).

Description. Monosiphonic colonies composed of a mass of branches and stems, irregularly branched in several planes and with anastomoses, up to 90 mm in diameter, with the appearance of closely knitted net. Hydrothecae arranged in decussate pairs forming four longitudinal rows of hydrothecae (figure 13A).

Hydrothecae immersed into the branches for approximately one-quarter of their volume and strongly curving outwards (figure 13A–D). Adcauline hydrothecal wall with a considerable free portion, adnate to internode for ca half or slightly more of its length. Free part of adcauline wall straight or slightly convex; abcauline wall concave. Hydrothecal aperture circular and tilted downwards; rim even and usually with numerous renovations.

Female and male gonothecae present, both inserting individually at hydrothecal base. Female gonotheca urn-shaped (figure 13E); basal part ovoid, widening distally, apex contracted into a short neck bearing the aperture. Male gonotheca fusiform (figure 13F), with a distal, cone-shaped neck provided with a small, circular aperture. Gonothecae with a few striae at base of neck.

Remarks. Staurotheca nonscripta is characterized by the long free portion of the adcauline hydrothecal wall, resembling S. antarctica in this character, though the hydrothecae of S. nonscripta are much larger. Moreover, the female gonothecae are completely different.

The hydrothecae of S. nonscripta also resemble those present in the glomulus of S. glomulosa , but the remaining hydrothecae of S. glomulosa are clearly distinguishable from those of S. nonscripta as their free adcauline wall is much shorter and the hydrothecae are larger.

Ecology and distribution. Staurotheca nonscripta is a shelf species. It had been found at depths from 206 to 640 m on stony bottoms (Peña Cantero et al., 1997). Our material comes from 15– 564 m. It may provide a substratum for other hydroids ( Halecium sp. , Hebella sp. and Symplectoscyphus sp. ). Peña Cantero et al. (1997) found fertile colonies in February, whereas in our material colonies with gonothecae were collected in January, February and November.

Staurotheca nonscripta seems to have an Antarctic–Patagonian distribution. It has been recorded along the south and east coasts of the Weddell Sea and off Elephant Island (Peña Cantero et al., 1997). Our material comes from off Cabo Penas (Tierra del Fuego) and the Ross Sea (off Cape Hallett, south of Coulman Island, north-west of Roosevelt Island , Cape Adare, the central basin and off Scott Coast) .