Oswaldella delicata Peña Cantero, Svoboda and Vervoort, 1997

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 : 823

Oswaldella delicata Peña Cantero, Svoboda and Vervoort, 1997

( figure 4)

Oswaldella delicata Peña Cantero et al., 1997: 353–355 , figures 3, 13C; Peña Cantero and Vervoort, 1998: 36; Peña Cantero and García Carrascosa, 1999: 214; Peña Cantero and Marques, 1999: 85.

? Oswaldella sp. 1 Peña Cantero and Vervoort, 1995: 334–336, figure 2.

Material examined. 001/011, two stems up to 60 mm high ( USNM 1003308; RMNH-Coel. 30206);? 32/2068, two stems up to 24 mm high ( USNM 1003309; RMNH-Coel. 30207).

Description. Colonies composed of monosiphonic and unbranched stems up to 60 mm high. Hydrocaulus provided with apophyses alternately arranged in one plane, forming two longitudinal rows; apophyses upwardly directed, forming an angle of ca 45 ° with long axis of stem ( figure 4A). Hydrocaulus divided into internodes; usually one apophysis per internode. Cauline apophyses provided with a single axillary nematophore, emerging through a simple perisarc hole ( figure 4B, C). Apophyses supporting unbranched hydrocladia separated by a distinct node ( figure 4A, B).

Hydrocladia homomerously divided into hydrothecate internodes provided with one hydrotheca and two nematophores ( figure 4B, D–H): one mesial superior, emerging through a perisarc hole situated behind free adcauline hydrothecal wall, and one mesial inferior springing from a perisarc hole in a slight elevation of internode and provided with a scale-shaped nematotheca. Distal hydrocladial internodes apically truncated.

Hydrotheca elongate, placed on middle of hydrocladial internode ( figure 4B, D–H); distinct part of its adcauline wall free. Abcauline hydrothecal wall straight, though convex basally. Hydrothecal aperture circular, more or less perpendicular to long axis of internode; rim even.

Gonothecae present in the material from Stn 32 / 2068 ( figure 4I), inserting on infrathecal elevation of hydrocladial internode, fusiform, provided with an almost circular, subterminal aperture; basal third with node or diaphragm.

Remarks. The material from Stn 32 / 2068 differs from O. delicata studied so far by the absence of internodes in the stems, the presence of an inconspicuous node between the cauline apophyses and the hydrocladia ( figure 4B), and the shape of the gonothecae ( figure 4I). The difference in gonothecal structure may be due to sexual dimorphism. In the original description of O. delicata only one type of gonotheca was found; sexual dimorphism is known to exist in species of Oswaldella .

Ecology and distribution. Oswaldella delicata was known only from 430 to 440 m depth off the south coast of the Weddell Sea, occurring on muddy bottom; colonies with gonothecae were collected in February (Peña Cantero et al., 1997). Our material was collected at 438 m depth, east of Cape Wheeler, off the south-west coast of the Weddell Sea.