Antarctoscyphus mawsoni ( Briggs, 1938 )

Peña Cantero, Álvaro L., Roig Ferrer, Estela & Miranda, Thais P., 2017, Species of Antarctoscyphus Peña Cantero, García Carrascosa and Vervoort, 1997 (Cnidaria: Hydrozoa: Symplectoscyphidae) collected by US Antarctic expeditions: biogeographic implications, Journal of Natural History (J. Nat. Hist.) 51 (25 - 26), pp. 1437-1477 : 1465

Antarctoscyphus mawsoni ( Briggs, 1938)

( Figure 12 )

Symplectoscyphus mawsoni Briggs, 1938, p. 35 , fig. 2a–b, pl. 16, figs 1–2.

Sertularella mawsoni – Naumov and Stepanjants, 1972, p. 46, fig. 8; Stepanjants, 1979, p. 67, pl. 11, fig. 3.

not Symplectoscyphus mawsoni – Millard, 1977, p. 29, figs 8–9 [=? Antarctoscyphus grandis ( Blanco, 1977) ].

Antarctoscyphus mawsoni – Peña Cantero et al., 1997, p. 26–7; Peña Cantero, 2014b, p. 1721, fig. 4i.

Material examined

Eltanin: 6/418, several stem fragments, up to 30 mm long; 12/1002, four fragments, up to 10 mm long; 12/1003, several stem fragments, up to 15 mm long; 22/1582, several fragments, up to 14 mm long; 32/1997, numerous fragments, up to 15 mm long. Hero : 731/1861, numerous stems, up to 140 mm high; 731/1944, a fragment, c. 3 mm long. Islas Orcadas: 575/066, many stem fragments, up to 80 mm long; 575/069, numerous fragments and stems, up to 85 mm high; 575/070, several stem fragments, up to 50 mm long; 575/073, several stem fragments, up to 85 mm long.

Diagnosis

Stems monosiphonic, unbranched, up to 115 mm high. Cauline internodes distinctly arranged in zigzag. Cauline apophyses alternately arranged in one plane. Paired branches arising almost at right angles from stem, short, little developed, usually unforked, each with up to 12 hydrothecae. Hydrothecae arranged alternately and almost in one plane. Hydrotheca strongly widening from its basal part upwards; maximum diameter at aperture; adcauline hydrothecal wall free. Hydrothecal aperture cusps of similar development and separated by shallow embayments. Gonothecae unknown.

Ecology

Found epibiotic on the hydrozoan Oswaldella stepanjantsae ( Peña Cantero 2014b) . We found it as basibiont for colonies of the hydroid Symplectoscyphus sp.

Bathymetric and geographic distribution

Eurybathic species previously found at depths between 6 m ( Naumov and Stepanjants 1972) and 527 m ( Peña Cantero 2014b); our material was collected between 70 and 1042 m, considerably extending its lower bathymetric limit to the upper slope.

Hitherto, Antarctoscyphus mawsoni was considered a species endemic to East Antarctica ( Peña Cantero 2014b), being known from Commonwealth Bay, George V Coast ( Briggs 1938), D’ Urville Sea, Adélie Land ( Naumov and Stepanjants 1972) and off Queen Mary Coast ( Peña Cantero 2014b). Our material is recorded off Cape Hallett (Victoria Land, Ross Sea), in East Antarctica, but also for different West Antarctic areas, clearly showing a Circum-Antarctic distribution of the species: off Visokoi and Zavodovski Islands ( South Sandwich Islands), off Elephant Island, and from several areas of the Antarctic Peninsula (Joinville Island, d’ Urville Island, Lavoisier Island, in the Biscoe Islands, and Anvers Island, in Palmer Archipelago).

Figures

Figure 12. Antarctoscyphus mawsoni (Briggs, 1938): (a) axillary hydrotheca and paired branches showing hydrothecal disposition; (b) distal part of cauline internode showing axillary hydrotheca and basal part of paired branches; (c, d) hydrothecae; (e) detail of hydrothecal aperture. Scale bars: 1 mm (a), 250 µm (b, c), 200 µm (d), 50 µm (e).