Halecium secundum Jäderholm, 1904

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 : 52

Halecium secundum Jäderholm, 1904

( Figs 15 H, 16D)

Halecium secundum —Peña Cantero et al., 2013: 747 fig. 6c; Peña Cantero, 2014b: 273 –274, fig. 4D–F (synonymy).

Material examined. Stn 52, polysiphonic stem 55 mm high (NIWA 117600); Stn 67, distal stem fragment 17 mm long (MNCN 2.03/652).

Measurements (in µm). Hydrothecae: diameter at aperture 215–250, diameter at diaphragm 210–240, height 20–25. Internodes: length 450–580, diameter at distal part 220–230. Hydrophore: length 75–100. Cnidome: microbasic euryteles? (12–13 x 6–6.5).

Remarks. Branches originate either from within a hydrotheca or from a hydrophore; frequently with short intermediate internodes following the apophysis ( Fig. 16 D). Hydrothecae are usually alternately arranged in two planes, forming an obtuse angle. The hydrotheca is at the end of an adnate hydrophore and its diameter barely increases distally; rim not everted ( Fig. 15 H). The adcauline side of the hydrotheca is usually little developed, not reaching the end of the internode.

Ecology and distribution. Recently reviewed by Peña Cantero (2014b). Shelf species found at depth between 40 (Peña Cantero et al. 2013) and 150 m ( Jäderholm 1904); present material between 152 and 286 m.

Circum-Antarctic distribution ( Peña Cantero 2014b). In the Ross Sea, already known from Tethys Bay (Peña Cantero et al. 2013). Present material collected off Cape Hallett.

Figures

FIGURE 15. Halecium banzare Watson, 2008: A, internodes with primary and second-order hydrothecae; B, gonotheca. Halecium exaggeratum Peña Cantero, Boero & Piraino, 2013: C, internode with primary and secondary hydrotheca as well as lower-order branch; D, internodes with primary hydrothecae; E, gonotheca. Halecium interpolatum Ritchie, 1907: F, internode with primary hydrotheca and internode structure. Halecium jaederholmi Vervoort, 1972: G, internodes with primary hydrothecae. Halecium secundum Jäderholm, 1904: H, internode with primary hydrotheca. (A from Stn 53; B from Stn 139; C – E, H from Stn 67; F from Stn 107; G from Stn 112). Scale bar: 250 µm.

FIGURE 16. Halecium exaggeratum Peña Cantero, Boero & Piraino, 2013: A, cauline internode with hydrophore and primary hydrotheca; B, gonotheca. Halecium pseudoincertus Peña Cantero, 2014: C, internode with primary and secondary hydrotheca. Halecium secundum Jäderholm, 1904: D, internodes with primary hydrothecae and branch origin with ahydrothecate intermediate internode. Scale bar: 100 µm (A), 200 µm (B – D).