Symplectoscyphus

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 : 46-47

Symplectoscyphus sp. 1

( Figs 12 J, 13C)

Material examined. Stn 7, stem 5 mm high on Schizotricha turqueti (MNCN 2.03/644); Stn 17, two stems up to 11 mm high on Schizotricha turqueti (NIWA 117589).

Description. Monosiphonic, straight stems, up to 11 mm high. Stem divided into short internodes (shorter than hydrothecae). Distal part of hydrotheca reaching basal part of following alternate one.

Hydrothecae ( Figs 12 J, 13C) relatively large, almost cylindrical, abcaudally directed. Adcauline hydrothecal wall adnate to internode for more than half its length. Free part of adcauline hydrothecal wall roughly straight; adnate part usually convex. Abcauline hydrothecal wall slightly convex basally, concave by the middle. Cusps of hydrothecal aperture sharp, separated by deep embayments.

Measurements (in µm). Hydrothecae: length abcauline wall 350–450, length free part of adcauline wall 230–300, length adnate part of adcauline wall 310–330, length adcauline wall 540–610, diameter at aperture 200–210, diameter at diaphragm 150–170, maximum diameter 220–240. Cnidome (from Stn 7): larger microbasic mastigophores, range 8.5–9.5 x 3.0–3.5, mean 9.0±0.2 x 3.1±0.2 (n=10); ratio, range 2.4–3.2, mean 2.9±0.2 (n=10).

Remarks. The scarcity of material and its infertile condition prevent me from characterizing completely this species. By the shape of the hydrothecae, it reminds of S. frigidus Peña Cantero, Svoboda & Vervoort, 2002 . However, hydrothecae are larger and the adcauline hydrothecal wall is adnate to the internode for less than half its length in S. frigidus ; it is adnate in more than half its length in the present material. This material is also morphologically close to S. cumberlandicus concerning the shape of some hydrothecae (cf., for instance fig. 3E in Peña Cantero et al. 2002), but it clearly differs in colony structure, as S. cumberlandicus forms polysiphonic colonies several centrimetres high. The material studied could actually represent incipient stems of species forming much larger stems.

Ecology and distribution. Material collected from depths between 420 and 536 m, off Possession Islands, epibiotic on Schizotricha turqueti .

Figures

FIGURE 12. Antarctoscyphus admirabilis Peña Cantero, Svoboda & Vervoort, 1999: A, branch internode with hydrotheca. Symplectoscyphus aggregatus (Jäderholm, 1917): B, fragment of branch with hydrothecal arrangement and shape. Symplectoscyphus anae Peña Cantero, Svoboda & Vervoort, 2002: C, internode with hydrotheca. Symplectoscyphus densus sp. nov.: D – E, fragment of branch with hydrothecal arrangement and shape; Symplectoscyphus exochus Blanco, 1982: F, internode with hydrotheca. Symplectoscyphus liouvillei (Billard, 1914): G, internode with hydrotheca. Symplectoscyphus vanhoeffeni Totton, 1930: H, internode with hydrotheca. Symplectoscyphus weddelli Peña Cantero, Svoboda & Vervoort, 2002: I, internode with hydrotheca. Symplectoscyphus sp. 1: J, internode with hydrotheca. Symplectoscyphus sp. 2: K, internode with hydrotheca. (A from Stn 17; B from Stn 112; C from Stn 126; D from Stn 7 (holotype); E from Stn 97 (paratype); F from Stn 67; G from Stn 150; H from Stn 130; I, from Stn 53; J from Stn 7; K from Stn 25). Scale bar: 250 µm.