Staurotheca densa Peña Cantero & Vervoort, 2003

ÁLVARO L. PEÑA CANTERO, 2017, Benthic hydroids (Cnidaria, Hydrozoa) from the Ross Sea (Antarctica) collected by the New Zealand Antarctic expedition BioRoss 2004 with RV Tangaroa, Zootaxa 4293 (1), pp. 1-65 : 29-31

Staurotheca densa Peña Cantero & Vervoort, 2003

( Fig. 10 B)

Staurotheca densa Peña Cantero & Vervoort, 2003: 2678 –2680, fig. 6 (synonymy); Peña Cantero, 2008: 459; 2009: 1749.

Material examined. Stn 24, fragment 7 mm long, in bad condition (NIWA 117520); Stn 25, four colonies up to 40 mm in diameter, with female gonothecae, basibiont of Rhizorhagium antarcticum (MNCN 2.03/552); Stn 48, two fragments, 20 and 14 mm long (NIWA 117521); Stn 52, fragment 20 mm long (NIWA 117522); Stn 53, one stem 55 mm high basibiont of Rhizorhagium antarcticum , and one fragment 18 mm long basibiont of Hebella plana (MNCN 2.03/553); Stn 63, mass of branches, ca. 60 mm long, with female gonothecae (NIWA 117523); Stn 67, three palmate colonies up to 160 mm high, mass of stems ca. 30 mm in diameter, and four fragments up to 42 mm long (MNCN 2.03/554); Stn 96, colony 85 mm long (NIWA 117524); Stn 123, colony fragment 70 mm long (MNCN 2.03/555); Stn 125, several fragments up to 28 mm long (NIWA 117525); Stn 126, six colonies up to 200 mm high and 130 mm wide, with male and female gonothecae, basibiont of Hebella plana , Lafoea dumosa , Symplectoscyphus anae Peña Cantero, Svoboda & Vervoort, 2002 , and Symplectoscyphus sp. (NIWA 117526); Stn 129, one fragment 6 mm long (NIWA 117527); Stn 130, 16 colonies up to 200 mm high and 120 mm wide, with male and female gonothecae, basibiont of Abietinella operculata , Antarctoscyphus spiralis , Billardia subrufa , Campanularia hicksoni , Halecium tangaroa sp. nov., Lafoea dumosa , Symplectoscyphus sp., and Rhizorhagium antarcticum (NIWA 117528); Stn 132, at least two colonies up to 190 mm high, with male and female gonothecae, basibiont of Halecium sp. and Sympletoscyphus sp. (MNCN 2.03/556); Stn 197, mass of stems ca. 70 mm in diameter, with female gonothecae (MNCN 2.03/557); Stn 198, two fragments up to 20 mm long (NIWA 117529).

Measurements (in µm). Hydrotheca: abcauline wall 680–730, free part of adcauline wall 260–360, adnate part of adcauline wall 500–590, adcauline wall 850–880, diameter at aperture 260–280. Larger nematocysts: 20–21.5 x 5.

Remarks. The colonies may be polysiphonic basally. Although this species typically has three to four hydrothecae per verticil, decussate pairs are occasionally found. This species is also characterized by having a slight, but distinct abcauline projection at the hydrothecal aperture ( Fig. 10 B).

Ecology and distribution. Reviewed by Peña Cantero & Vervoort (2003). Shelf species found at depths between 73 and 570 m ( Peña Cantero & Vervoort 2003); present material from 110 to 736 m, increasing its lower bathymetric limit, basibiont for colonies of Abietinella operculata , Antarctoscyphus spiralis , Billardia subrufa , Campanularia hicksoni , Halecium tangaroa sp. nov., Halecium sp., Hebella plana , Lafoea dumosa , Rhizorhagium antarcticum , Symplectoscyphus anae , and Symplectoscyphus sp., and with gonothecae in February.

Circum-Antarctic species ( Peña Cantero & Vervoort 2003), recently recorded from off Trinity Island ( Peña Cantero 2008) and from the Balleny Islands (Peña Cantero 2009). See Peña Cantero & Vervoort (2003) for previous records. In the Ross Sea, already known off Cape Hallett and Pennell Bank ( Peña Cantero & Vervoort 2003). Present material from Robertson Bay and off Cape Adare, Adare Peninsula, Possession Islands and Cape Hallett.

Figures

FIGURE 10. Staurotheca compressa Briggs, 1938: A, hydrotheca. Staurotheca densa Peña Cantero & Vervoort, 2003: B, hydrotheca. Staurotheca dichotoma Allman, 1888: C, hydrotheca. Staurotheca gracilis sp. nov.: D, basal part of a branch with hydrothecal arrangement; E – G, hydrothecae. Staurotheca nonscripta Peña Cantero, Svoboda & Vervoort, 1997: I, hydrotheca. (A, from Stn 178; B from Stn 67; C, from Stn 140; D – E, G – H from the holotype; F from the paratype; I from Stn 148). Scale bar: 250 µm (A – C, E – H), 500 µm (D).