Filellum antarcticum ( Hartlaub, 1904 )

Peña Cantero, Álvaro L., 2021, Additions to knowledge of the biodiversity of benthic hydroids (Cnidaria: Hydrozoa) in the Balleny Islands (Antarctica), Zootaxa 4966 (3), pp. 321-336 : 323

Filellum antarcticum ( Hartlaub, 1904)

( Fig. 1A–C )

Material examined. E203, several hydrothecae and two coppiniae, on Stegella lobata ( Vanhöffen, 1910) ( NIWA 128467).

Remarks. The presence of coppinia in the present material allows identification with confidence. The nestshaped coppinia consists of closely packed gonothecae ( Fig. 1A ) surrounded by a fence of distally open defensive tubes arching over them. The gonothecae are deprived of distal neck ( Fig. 1B ). Some of them, however, with distal part slightly raised ( Fig. 1C ), but never forming a distally everted neck as found in the other known Antarctic species of the genus, Filellum magnificum Peña Cantero, Svoboda & Vervoort, 2004 . The gonotheca is roughly 260 µm high, 130 µm in maximum diameter, and 65–70 µm in diameter at aperture. The shape and size of the hydrothecae in the present material also match Hartlaub’s species, with a hydrothecal diameter of 100–120 µm.

Ecology and distribution. The material, which represents the first record for the area, was collected at a depth of 187 m off Sturge Island, epibiotic on S. lobata . Coppiniae in January.

Figures

FIGURE 1. Filellum antarcticum (Hartlaub, 1904): A, part of a coppinia showing gonothecal arrangement; B–C, distal part of gonothecae showing aperture (arrows). Lafoea dumosa (Fleming, 1820): D, hydrotheca and pedicel. Phialella belgicae (Hartlaub, 1904): E, hydrotheca and pedicel. Campanularia sp.: F, hydrotheca; G, distal part of pedicel, basal spherule and basal chamber with diaphragm. Antarctoscyphus elongatus (Jäderholm, 1904): H, internode with hydrotheca. Scale bar: 100 µm (B, C, G), 200 µm (A, D–F, H).