Oswaldella delicata Peña Cantero, Svoboda & Vervoort, 1997

Molinero, A. González & Peña Cantero, A. L., 2015, SEM study of species of Oswaldella Stechow, 1919 (Cnidaria, Hydrozoa, Kirchenpaueriidae), with an annotated checklist of the species of the genus, Zootaxa 4052 (4), pp. 401-441 : 403-406

Oswaldella delicata Peña Cantero, Svoboda & Vervoort, 1997

( Figs 2 , 16 B, 17B, 19B)

Material examined. Spanish Antarctic Expedition Bentart 95: Stn 28A, BIO Hespérides, 2 February 1995, 62°12.1297’S, 60°23.1833’W (South Shetland Islands, north of Livingston Island), 126 m (Department of Zoology, University of Valencia, BENTART 95-28A).

Description. Monosiphonic, unbranched stems, up to 60 mm high, divided into internodes. Angle between cauline apophyses and stem ca. 45°. Cauline apophyses with single axillary nematophore, emerging through perisarc hole provided with very short collar-shaped nematotheca ( Fig. 2 B, C).

Hydrocladia unbranched ( Fig. 2 A), some bifurcated. First hydrocladial internode bifurcated, with two similar prongs. Mesial superior nematophore emerging behind free part of adcauline hydrothecal wall. Mesial inferior nematophore on a strongly marked swelling at proximal third of internode; with well-developed, nail-shaped nematotheca ( Fig. 2 D–F). Hydrotheca elongate, placed on middle of internode. Adcauline wall with distinct free portion. Abcauline hydrothecal wall roughly straight, but basally convex ( Fig. 2 E). Hydrothecal aperture circular, more or less perpendicular to long axis of internode ( Fig. 2 D–E); rim even.

Gonothecae fusiform with subterminal circular aperture.

Remarks. Our study has confirmed the presence of a single axillary nematophore in the cauline apophyses, as previously described (Peña Cantero et al. 1997; Peña Cantero & Vervoort 2004). However, it is noteworthy that our study has provided evidence of the presence of a little-developed, previously unnoticed, collar-shaped nematotheca associated with that nematophore ( Fig. 2 B–C).

Figures

FIGURE 2. Oswaldella delicata Peña Cantero, Svoboda & Vervoort, 1997. A, fragment of hydrocladium showing hydrothecal arrangement; B – C, cauline apophysis with axillary nematophore (B lateral view, C upper view); D – E, hydrocladial internodes showing hydrotheca and mesial inferior nematotheca (D frontal view, E lateral view); F, detail of mesial inferior nematotheca. Scale bar: 400 µm (A), 60 µm (D – E), 20 µm (B) and 10 µm (C – F).

FIGURE 16. Detail of the area from which mesial nematophore emerges. A, Oswaldella bifurca; B, Oswaldella delicata; C, Oswaldella elongata; D, Oswaldella erratum; E, Oswaldella frigida; F, Oswaldella garciacarrascosai; G, Oswaldella grandis; H, Oswaldella incognita; I, Oswaldella laertesi; J, Oswaldella niobae; K, Oswaldella rigida; L, Oswaldella shetlandica; M, Oswaldella stepanjantsae; N, Oswaldella vervoorti; O, Oswaldella sp. Scale bar: 20 µm (A – O).