Oswaldella terranovae Peña Cantero & Vervoort, 1996

Soto, Joan J. & Peña, Álvaro L., 2019, Benthic hydroids (Cnidaria, Hydrozoa) from the Weddell Sea (Antarctica), Zootaxa 4570 (1), pp. 1-78 : 47-49

Oswaldella terranovae Peña Cantero & Vervoort, 1996

( Fig. 17 a–f)

Material examined. ANT XV/3: 48-27, several stems, up to 110 mm high; 48-31, few colonies, up to 80 mm high, some on stone; 48-33, several colonies, up to 170 mm high, some on stone; 48-34, one colony, up to 150 mm high, on sponge, with developing gonothecae; 48-36, few colonies, up to 120 mm high, with gonothecae; 48-50, several stems, up to 100 mm high; 48-63, several stems, up to 170 mm high; 48-210, several stems, up to 70 mm high, on stone and gravel, with developing gonothecae; 48-276, several stems, up to 110 mm high; ANT XVII/3: 111-5, several stems, up to 130 mm high, on gravel, with gonothecae; 111-6, several stems, up to 100 mm high; 111-7, several stems, up to 120 mm high, with developing gonothecae; 111-9, few stems, up to 60 mm high, with gonothecae; 111-18, few colonies, up to 210 mm high, with gonothecae; ANT XXI/2: PS65/251, few colonies, up to 115 mm high, on gravel and stone; PS65/278, few stems, up to 130 mm high; PS65/281, few colonies, up to 110 mm high, with gonothecae.

Remarks. [Note: Recently, Peña Cantero and González Molinero (2018) demonstrated that the ubiquitous Oswaldella stepanjantsae Peña Cantero, Svoboda & Vervoort, 1997 is a junior synonym of the uncommon Oswaldella terranovae Peña Cantero & Vervoort, 1996 ]. Among the abundant material examined, we found some small fragments with caulinar apophyses in spiral arrangement forming three longitudinal rows ( Fig. 17e ). In one case, a transition between triseriate and biseriate arrangement has been observed. Hitherto, triseriate apophyses are extremely rare amongst members of the family Kirchenpaueriidae (cf. Peña Cantero 2007), only documented in a single Antarctic representative of the genus Oswaldella : Oswaldella laertesi Peña Cantero, 2007 , in which the triseriate disposition is constant. The fragments studied are clearly referable to O. terranovae because up to six axillary nematophores have been observed on the caulinar apophyses, and the abcauline wall of the hydrotheca is clearly longer than its aperture (cf. Peña Cantero & Vervoort 2004, as Oswaldella stepanjantsae ). Oswaldella laertesi has low hydrothecae, and up to four axillary nematophores ( González Molinero and Peña Cantero 2015). Present study evidence that at least two species of Kirchenpaueriidae belonging to the genus Oswaldella present apophyses in a triseriate arrangement, although in O. terranovae the biseriate disposition is the rule. Present finding could point to a putative phylogenetic relationship between the two species.

Ecology and distribution. Species collected at depths between 36 and 1890 m ( Peña Cantero & Vervoort 2004, as Oswaldella stepanjantsae ); present material between 62 and 417 m. As pointed out by Peña Cantero (2013, 2014a, as O. stepanjantsae ), and evidenced here, this species serve as basibiont for a great diversity of epibiotic hydrozoans, as well as other several taxa (cf. Tab. 3), thus constituting an important habitat former. Species with a circum-Antarctic distribution ( Peña Cantero & González Molinero 2018).

Figures

FIGURE 17. a–f Oswaldella terranovae: a hydrotheca in lateral view; b hydrotheca in frontal view; c–d cauline apophysis showing nematophores; e hydrocaule with apophyses in triseriate arrangement; f male gonotheca in frontal view. g–m O. tottoni: g hydrotheca in lateral view; f hydrotheca in frontal view; i colony; j detail of the stem showing hydrocladial arrangement; k female gonootheca in lateral view; l male gonotheca in lateral view; m female gonotheca in frontal view (left) and male gonotheca in frontal view (right).