Staurotheca dichotoma Allman, 1888

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 : 31

Staurotheca dichotoma Allman, 1888

( Fig. 10 C)

Staurotheca dichotoma— Totton, 1930: 178, fig. 27a, c, pl. 2 fig. 9; Peña Cantero & Vervoort, 2003: 2681 –2683, fig. 7 (synonymy); Peña Cantero & Gili, 2006: 768; Peña Cantero, 2010b: 769; 2012: 859; Soto Àngel & Peña Cantero, 2015: 998, fig. 8d–e.

Material examined. Stn 8, fragment 15 mm long (MNCN 2.03/558); Stn 140, mass of stems ca. 60 mm in diameter, basibiont of Hebella plana (NIWA 117530).

Remarks. In the material examined the hydrothecae are arranged in decussate pairs and have a significant free portion (about 200 µm). This is a species characterized by having quite robust hydrothecae ( Fig. 10 C) with a relatively large diameter at the hydrothecal aperture (300–320 µm in the present material). The larger microbasic mastigophores are 19–22 x 4–4.5 µm.

Ecology and distribution. Reviewed by Peña Cantero & Vervoort (2003). Found at depths from 82 ( Totton 1930) to 799 m ( Peña Cantero et al. 1997a); present material from 231 to 541 m, basibiont for colonies of Hebella plana .

Species with an Antarctic–Kerguelen distribution ( Peña Cantero & Vervoort, 2003), recently reported from off Bouvet Island ( Peña Cantero & Gili 2006), Peter I Island ( Peña Cantero 2010b), South Georgia, South Sandwich Islands and Discovery Bank ( Soto Àngel & Peña Cantero 2015) and from the Bellingshausen Sea ( Peña Cantero 2012). See Peña Cantero & Vervoort (2003) for previous records. In the Ross Sea, already known from McMurdo Sound and off Cape Adare ( Totton 1930) and from the central basin and at Pennell Bank ( Peña Cantero & Vervoort 2003). Present material off Possession Islands and Moubray Bay

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).