Oswaldella herwigi El Beshbeeshy, 2011

Cantero, A. L. Peña & Molinero, A. González, 2018, On several species of Oswaldella Stechow, 1919 (Cnidaria, Hydrozoa), including the description of a new species, Zootaxa 4457 (3), pp. 397-414 : 402

Oswaldella herwigi El Beshbeeshy, 2011

( Fig. 3 )

Oswaldella herwigi El Beshbeeshy, 1991: 259 –265, fig. 66 (nomen nudum); 2011: 197–201, fig. 66; Peña CanTerO et al., 1997: 344; Peña CanTerO & García CarrascOsa, 1998: 179; 1999: 214; Peña CanTerO & VerVOOrT, 1998: 36; 2004: 835–837, fig.

10; Peña CanTerO & Marques, 1999: 85; GOnzález MOlinerO & Peña CanTerO, 2015: 436; Miranda et al., 2016: 596 – 597.

Material examined. Patagonia 0 210, Stn DR 4, 20 February 2010, 41.983007 S, 57.974475 W, several stems up to 120 mm high.

Description. Monosiphonic, unbranched stems, up to 120 mm high, divided into internodes (one apophysis per internode). Cauline apophyses alternately arranged in one plane. Angle between cauline apophyses and stem ca. 45°. Cauline apophyses with an axillary nematophore emerging through a hole in perisarc ( Fig. 3B–C ), and another one emerging through a ‘mamelon’, which may be little marked ( Fig. 3B ) or even absent.

Distinct node between cauline apophyses and hydrocladia ( Fig. 3B–C ). Up to third-order hydrocladia present ( Fig. 3A ). Hydrocladia with asymmetrical arrangement, with main primary hydrocladium giving rise to several second-order hydrocladia ( Fig. 3A ). Some of these giving rise to a third-order hydrocladium at their first hydrothecate internode ( Fig. 3A ). Hydrocladia heteromerously divided into an alternate series of athecate and hydrothecate internodes ( Fig. 3A ). Mesial-inferior nematophore emerging from distinct swelling at proximal third of internode ( Fig. 3D–F ) and provided with a scale-shaped nematotheca ( Fig. 3D, F ). Hydrotheca placed on distal half of hydrothecate internodes ( Fig. 3A, D–E ). Hydrotheca low, about as high as wide. Abcauline hydrothecal wall straight or slightly convex. Adcauline hydrothecal wall with conspicuous free portion. Hydrothecal aperture circular, perpendicular to long axis of internode or abcaudally directed; rim even ( Fig. 3D–E ).

Immature gonothecae cone-shaped ( Fig. 3G ).

Remarks. According to Peña Cantero & Vervoort (2004) the ‘mamelon’ in Oswaldella herwigi is provided with a distal conical structure not seen in the remaining species of the genus (see Fig. 10D in Peña Cantero & Vervoort 2004). In the material examined here, we did not observe that conical structure; ‘mamelons” observed were similar to those found in other species of Oswaldella . However, we noticed that gonothecae might form on the cauline apophyses and, in some cases, directly from the ‘mamelon’. Very incipient gonothecae create a sort of structure ( Fig. 3C ) that could be that observed by those authors using optical microscopy.

Oswaldella herwigi is the only known species of the genus with heteromerous hydrocladial division, having alternating thecate and athecate internodes.

Distribution. Oswaldella herwigi is the only species of the genus found outside Antarctic waters. It is considered endemic to the Patagonian region ( El Beshbeeshy 2011).

Figures

FIGURE 3. Oswaldella herwigi El Beshbeeshy, 2011. A, hydrOcladial branching and dispOsiTiOn Of hydrOThecae; B–C, cauline apOphyses wiTh axillary nemaTOphOre and ‘mamelOn’; D–E, unfOrked hydrOcladial inTernOdes (D frOnTal View, E laTeral View); F, deTail Of mesial inferiOr nemaTOTheca; G, immaTure gOnOTheca. Scale bar: 200 µm (A), 100 µm (D–E), 40 (G), 20 µm (B–C, F).