Oswaldella herwigi 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 : 835-837

Oswaldella herwigi El Beshbeeshy, 1991

( figure 10) Oswaldella herwigi El Beshbeeshy, 1991: 259–265 , figure 66; Peña Cantero et al., 1997: 344;

Peña Cantero and García Carrascosa, 1998: 179; 1999: 214; Peña Cantero and Vervoort,

1998: 36; Peña Cantero and Marques, 1999: 85.

Material examined. 11/958, numerous stems up to 24 mm high (USNM 1003330; RMNH-Coel. 30215; MNCN 2.03 / 235); 6/339, two stem fragments up to 20 mm long (USNM 1003331); 6/340, several stems a few millimetres high (USNM 1003332); 6/342, two incipient stems (USNM 1003333).

Description. Stem monosiphonic, either branched or unbranched. Hydrocauli provided with alternately arranged apophyses, forming two longitudinal series, sometimes arranged in two planes meeting at an obtuse angle (up to 90 °) ( figure 10B, C). Apophyses directed upwards at an angle of ca 45 ° with long axis of stem. Each apophysis provided with an axillary nematophore emerging through a simple perisarc hole and a second nematophore emerging through a ‘mamelon’ situated on one side of the apophysis ( figure 10 B–D). Stem divided into internodes with one apophysis each.

Cauline apophyses supporting hydrocladia separated by a distinct node ( figure 10B, C). Second-order hydrocladia present ( figure 10A); in one stem with incipient third-order hydrocladia. Hydrocladial arrangement asymmetrical ( figure 10A); first-order hydrocladia giving rise to several secondary hydrocladia. Top of distal hydrocladial internodes truncated.

Hydrocladia heteromerously segmented ( figure 10), with alternately arranged athecate and hydrothecate internodes. Hydrothecate internodes with one hydrotheca and two nematophores ( figure 10 E–G): one mesial inferior emerging through a perisarc hole on a slight elevation of internode and provided with a scale-shaped nematotheca, and a mesial superior nematophore emerging through a perisarc hole situated behind the free adcauline hydrothecal wall.

Hydrothecae usually situated on distal half of hydrothecate internodes; sometimes in the middle ( figure 10A, C, E, G). Hydrotheca shallow, rim circular and slightly laterally depressed, tilted downwards. Considerable part of adcauline wall of hydrotheca free; abcauline wall at an angle of ca 60 ° with internodal long axis.

Gonothecae absent.

Remarks. Oswaldella herwigi is the only species of the genus found outside Antarctic waters (cf. figure 19). It also has peculiarities in which it differs from the remaining species of Oswaldella . For example, the ‘mamelon’ present on the cauline apophyses of this species has a structure different from that of the other species, as it is provided with a conical distal structure ( figure 10D) that is absent in the remaining species. Moreover, the naked nematophores, i.e. the mesial superior nematophore situated behind free adcauline hydrothecal wall and the axillary nematophore of the cauline apophyses appear to be sheathed ( figure 10C, E–G). Oswaldella herwigi is also the only species with heteromerously divided hydrocladia, having alternating hydrothecate and athecate internodes.

In two stems from Stn 6 / 340 the cauline apophysis of the first stem internode has two axillary perisarc holes. In the second internode, those axillary holes are partly merged. In the remaining cauline apophyses there is a single axillary perisarc hole. This phenomenon is similar to that observed in other species of the genus (e.g. O. bifurca ) and points to a certain inconsistency in the number of axillary nematophores.

Ecology and distribution. Oswaldella herwigi is endemic to the Patagonian region ( El Beshbeeshy, 1991), having been collected at depths from 90 to 1000 m on the Patagonian shelf and slope ( El Beshbeeshy, 1991). Our material comes from depths of 44 to 586 m off the Falkland Islands and the western mouth of the Strait of Magellan. We found it growing as an epibiont on hydroids ( Nemertesia sp. and Aglaopheniidae ).