Oswaldella, Stechow, 1919

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 : 852-855

Oswaldella sp. 1

( figure 17)

Material examined. 6/416, one stem broken into two fragments (35 and 20 mm long) (USNM 1003384); 6/426, a few stems up to 70 mm high (USNM 1003385; RMNH-Coel. 30234); 6/428, one stem ca 18 mm high (USNM 1003386); 6/445, two fragments of one stem (USNM 1003387); 691/023, three basally broken stems up to 25 mm high (USNM 1003388; RMNH-Coel. 30235); 691/24, two stems up to 15 mm high (USNM 1003389).

Description. Colonies composed of monosiphonic and unbranched stems up to 70 mm high. Hydrocaulus with apophyses alternately arranged in one plane, forming two longitudinal rows and directed upwards, forming an angle of ca 45 ° with long axis of stem ( figure 17A). Cauline apophyses provided with two axillary nematophores, each one emerging from a simple perisarc hole ( figure 17B). Hydrocaulus divided into internodes ( figure 17A); one to three apophyses per internode, each apophysis supporting an unbranched hydrocladium ( figure 17A), though secondary hydrocladia are also present ( figure 17B). A distinct node separating cauline apophyses and hydrocladia ( figure 17A, B).

Hydrocladia homomerously divided into internodes, each with one hydrotheca and two nematophores ( figure 17 C–K): one mesial superior, emerging from a simple perisarc hole behind free adcauline hydrothecal wall, and one mesial inferior nematophore with a much-reduced, scale-shaped nematotheca emerging from a perisarc hole in an elevation of the internode. Top of distal hydrocladial internodes truncated.

Hydrotheca elongate, situated approximately in the middle of hydrocladial internode ( figure 17 C–K), provided with a long free part of its adcauline wall (up to half of its length). Abcauline hydrothecal wall straight, though slightly convex basally; sometimes with a slight concavity at distal end. Hydrothecal aperture with circular and even rim, approximately perpendicular to long axis of internode.

Gonothecae absent.

Remarks. Oswaldella sp. 1 is allied to O. delicata (cf. table 1), sharing with it the general appearance and structure of the colony. These two differ in the number of axillary nematophores; in O. delicata there is a single axillary nematophore, in Oswaldella sp. 1 there are two, each one emerging from a perisarc hole. They also differ in greater length of the free adcauline hydrothecal wall in Oswaldella sp. 1. Additional fertile material is necessary to define the systematic status of the present material.

Ecology and distribution. Oswaldella sp. 1 was found at depths from 93 to 507 m near the Antarctic Peninsula: off Brabant Island (Palmer Archipelago), north-east of Livingston Island (South Shetland Islands) and north of d’Urville Island and Penguin Island (Bransfield Strait).