Oswaldella erratum Peña Cantero & 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 : 406-409

Oswaldella erratum Peña Cantero & Vervoort, 1997

( Figs 4 , 16 D, 17D, 19D)

Material examined. German Antarctic Expedition ANT-XXI/2: Stn PS65 /166-1, Polarstern, 15 December 2003, 70°56.83’–70°56.00’, 10°32.61’– 10°30.53’W (off Cape Norvegia, Weddell Sea), 338– 253 m. Spanish Antarctic Expedition Bentart 95: Stn 24R, Hespérides, 30 January 1995, 63°58.4715’S, 60°51.9882’W (off Trinity Island, Graham Land), 214 m (Department of Zoology, University of Valencia, BENTART 95-24R).

Description. Monosiphonic (occasionally polysiphonic), unbranched stems, up to 130 mm high, usually not divided into internodes. Typically, perisarc strongly developed. Angle between cauline apophyses and stem ca. 70°. Cauline apophyses with two axillary nematophores, each provided with a much-reduced nematotheca ( Fig. 4 B).

Hydrocladia branched, up to third-order hydrocladia reported. First hydrocladial internode bifurcated, with two similar prongs ( Fig. 4 A). Mesial-inferior nematophore on a strongly marked swelling at proximal third of internode ( Fig. 4 D–E); with scale-shaped nematotheca ( Fig. 4 D–F). Hydrotheca elongate, placed on middle of internode ( Fig. 4 A, D–E). Abcauline wall of hydrotheca basally straight, but strongly curving adcaudally at distal part ( Fig. 4 E). Hydrothecal aperture kidney-shaped ( Fig. 4 C), adcaudally directed ( Fig. 4 E).

Gonothecae fusiform. Female gonotheca larger than male one, with subterminal, circular aperture. Male gonotheca with distal, circular aperture ( Fig. 4 G).

Remarks. The most remarkable finding in relation to this species is the presence of much-reduced nematothecae in the axillary nematophores, never described before.

Figures

FIGURE 4. Oswaldella erratum Peña Cantero & Vervoort, 1997. A, hydrocladial branching and disposition of hydrothecae; B, cauline apophysis with axillary nematophores; C, unforked hydrocladial internode showing hydrothecal aperture and mesial superior and mesial inferior nematophores; D – E, unforked hydrocladial internodes (D frontal view, E lateral view); F, detail of mesial inferior nematotheca; G, gonotheca. Scale bar: 400 µm (A), 200 µm (F), 80 µm (D – E), 50 µm (B – C) and 20 µm (G).

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).