Oswaldella stepanjantsae El Beshbeeshy, 1991

Peña Cantero, A. L. & Vervoort, W., 2004, Species of Oswaldella Stechow, 1919 (Cnidaria: Hydrozoa: Kirchenpaueriidae) from US Antarctic expeditions, with the description of three new species, Journal of Natural History 38, pp. 805-861 : 847-850

Oswaldella stepanjantsae El Beshbeeshy, 1991

( figure 15)

Oswaldella stepanjanti El Beshbeeshy, 1991: 263 , 265 (incorrect original spelling). Oswaldella stepanjantsae Peña Cantero et al., 1997: 344 , 376–380, figures 11, 15D; Peña

Cantero and Vervoort, 1998: 36; Peña Cantero and García Carrascosa, 1999: 214; Peña Cantero and Marques, 1999: 85 (justified emendation).

Oswaldella antarctica: Broch, 1948: 13–16 , figure 4a; Stepan’yants, 1979: 112, pl. 21 figure 5.

Oswaldella antarctica p.p.: Naumov and Stepan’yants, 1972: 52, figure 14a, b.

Material examined. 000AG, one stem at least 210 mm high ( USNM 1003359); 000AH, one fragmented stem, at least 220 mm high, with gonothecae ( USNM 1003360; RMNH-Coel. 30224); 00DAF, several stems of at least 300 mm high ( USNM 1003361; RMNH-Coel. 30225); 00DAQ, four stems up to 320 mm high ( USNM 1003362); 12/1003 several fragments up to 32 mm long ( USNM 1003363); 27/1896, numerous stem fragments up to 100 mm long, with immature gonothecae ( USNM 1003364; RMNH-Coel. 30226; MNCN 2.03 / 242); 32/2080, one fragmented stem (largest fragment ca 120 mm long) ( USNM 1003365; RMNH-Coel. 30227); 32/2082; three stem fragments up to 50 mm long ( USNM 1003366); 32/2121, numerous stem fragments up to 70 mm long, with gonothecae ( USNM 1003367); 32/2125, one fragmented stem (largest fragment up to 90 mm long), with gonothecae ( USNM 1003368; RMNH-Coel. 30228; MNCN 2.03 / 243); 6/418, several fragments up to 50 mm long, with gonothecae ( USNM 1003369); 691/26, numerous fragments up to 220 mm long ( USNM 1003370; RMNH-Coel. 30229; MNCN 2.03 / 244); 767, two stem fragments up to 60 mm long ( USNM 1003371); 833/018-1, one stem ca 500 mm high ( USNM 1003372; RMNH-Coel. 30230; MNCN 2.03 / 245).

Description. Colonies consisting of polysiphonic and branched stems. Hydrocauli provided with apophyses alternately arranged in two longitudinal series, directed upwards, forming an angle of ca 45 ° with long axis of stem. Hydrocaulus divided into internodes with one apophysis each; nodes, situated just above apophyses, often incomplete, as a result many internodes apparently with two apophyses. Cauline apophyses typically provided with two dorsal nematophores ( figure 15B), each one emerging through a ‘mamelon’ which may occasionally be absent (for instance in the material from Stn 6 / 418), and from two to six axillary nematophores ( figure 15B) emerging through simple perisarc holes. Cauline apophyses supporting hydrocladia ( figure 15A) from which they are separated by a distinct node, usually followed by a series of short, athecate internodes. Up to fourth-order hydrocladia present; hydrocladial arrangement symmetrical ( figure 15A).

Hydrocladia homomerously segmented; all internodes hydrothecate with one hydrotheca in middle of internode and two nematophores ( figure 15 C–H): one mesial inferior emerging through a perisarc hole on slight elevation of internode and provided with a scale-shaped nematotheca, and another mesial superior nematophore emerging through a perisarc hole behind free portion of adcauline hydrothecal wall. Top of distal hydrocladial internodes truncated.

Hydrotheca elongate ( figure 15 C–H); rim circular and even, slightly tilted adcaudally. Adcauline wall of hydrotheca with distinct free portion; abcauline wall straight.

Gonothecae present, inserting on infrathecal elevation of hydrocladial internodes, fusiform, with subterminal aperture ( figure 15I).

Remarks. Oswaldella stepanjantsae is well characterized by the general appearance of the colony, by the presence of two ‘mamelons’ and two to six axillary nematophores on the cauline apophyses (cf. table 1), and by the shape of hydrothecae and gonothecae.

Ecology and distribution. Oswaldella stepanjantsae has been found at depths between 50 and 600 m ( Broch, 1948); our material comes from 36 to 1890 m. It occurred on muddy, sandy and stony bottoms and on bottoms composed of mud and sand or small stones ( Broch, 1948). It has been found with gonothecae in January and February (Peña Cantero et al., 1997); our fertile material was collected in January, February and December. It is used as a substratum by other hydroids: Peña Cantero et al. (1997) found colonies of Hydractinia sp., Halecium sp. and we have observed colonies of Abietinella sp., Billardia subrufa , Campanularia sp., Filellum sp., Hydractinia sp., Sertularella sp. and Symplectoscyphus sp.

Oswaldella stepanjantsae is a circum-Antarctic species (Peña Cantero and Vervoort, 1998). It was known from off Elephant and Peter I Islands ( Broch, 1948) and the eastern coast of the Weddell Sea (Peña Cantero et al., 1997), in West Antarctica, and from off Adélie Land (cf. Peña Cantero et al., 1997) in East Antarctica. Our material comes from the Wilkes Land region, the Ross Sea and the Antarctic Peninsula area. In Wilkes Land, it was found north of Wilkes Station (Budd Coast). In the Ross Sea, O. stepanjantsae was collected in the central basin, off Franklin Island, Cape Adare, and at the Balleny Islands. Finally, near the Antarctic Peninsula it was found north-east of Joinville Island, north of D’Urville Island and south of Low Island.