Antarctoscyphus asymmetricus Peña Cantero, García Carrascosa and Vervoort, 1997

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 : 1446-1448

Antarctoscyphus asymmetricus Peña Cantero, García Carrascosa and Vervoort, 1997

( Figure 3 )

Symplectoscyphus sp. 1 Peña Cantero, 1991, p. 153–6, pls 26, 54, 67, fig. c; Peña Cantero and García Carrascosa, 1994, p. 125, fig. 7e–g; 1995, p. 84–7, figs 36A–E, 37A–E, 64C.

Antarctoscyphus asymmetricus Peña Cantero et al., 1997, p. 27 –8, figs 1a–f, 3b; Peña Cantero, 2006, p. 938, fig. 3I; 2008, p. 458; 2010, p. 768, fig. 5a; 2013, p. 130; Peña Cantero and Vervoot, 2009, p. 86.

Material examined

Eltanin: 12/1003, numerous fragments, up to 45 mm long, with gonothecae; 32/2125, several stem fragments, up to 35 mm long. Glacier: SOSC-L 54, several stem fragments, up to 50 mm long, basibiont of Halecium sp. Hero : 702/464, a few stem fragments, up to 70 mm long; 721/704, three stem fragments, up to 40 mm long; 721/776, one stem, c. 100 mm high; 721/1077, one branch fragment, c. 5 mm long. Islas Orcadas: 575/097, several fragments, up to 20 mm long; 876/109, one stem, c. 100 mm high, with gonothecae; 876/111, one stem, c. 100 mm high, with gonothecae; Pr Siedlecki: 601/ 006, one stem, c. 115 mm high, with female gonothecae; 601/008, several stems, up to 140 mm high, with gonothecae, on gravel; 601/011, numerous stems, up to 130 mm high, with gonothecae; 601/012, several stems, up to 160 mm high, with gonothecae; 601/014, five stems, up to 140 mm high, with gonothecae; 601/015, several stem fragments, up to 110 mm long, with female gonothecae; 601/016, five stems, up to 90 mm high, with gonothecae.

Diagnosis

Stems monosiphonic, up to 180 mm high. Cauline internodes with a distinct zigzag arrangement. Paired branches recurrently branching alternately in one plane and at each third internode. Hydrothecae alternately arranged in two planes forming an obtuse angle. Hydrotheca nearly straight. One abcauline cusp of hydrothecal aperture strongly developed; other cusps at rim small and blunt. Adnate portion of adcauline hydrothecal wall highly variable, from about half its length to almost completely adnate. Female gonotheca club-shaped, without pedicel and with circular, distal aperture. Male gonotheca fusiform, with peduncle and small, circular, distal aperture.

Remarks

This species is morphologically close to A. elongatus (see below), but easily distinguishable by the strong development of one of the adcauline cusps.

Ecology

Antarctoscyphus asymmetricus has been reported epibiotic on the ascidian Cnemidocarpa verrucosa ( Peña Cantero 2010) and as substrate for colonies of the hydrozoan Sertularella sanmatiasensis ( Peña Cantero 2013) ; we observed it epilithic on gravel and as basibiont of the hydroid Halecium sp. Previously found with gonothecae in January (Peña Cantero et al. 1997) and February ( Peña Cantero and Vervoort 2009; Peña Cantero 2013); we observed gonothecae in colonies collected in February, March, November and December.

Bathymetric and geographic distribution

Previously known from depths between 70 and 429 m ( Peña Cantero 2008); present material collected at depths from 18 to 342 m.

Hitherto, this species was considered to have a West Antarctic distribution (Peña Cantero 2006). It had been reported from off South Georgia (Peña Cantero et al. 1997), Elephant Island (Peña Cantero et al. 1997; Peña Cantero and Vervoort 2009), from the South Shetland Islands (Peña Cantero et al. 1997; Peña Cantero 2006, 2008), off Deception Island ( Peña Cantero 2008), Bransfield Island (Antarctic Peninsula) ( Peña Cantero and Vervoort 2009), Low Island ( Peña Cantero 2013) and off Peter I Island, in the Bellingshausen Sea ( Peña Cantero 2010). We also recorded material from West Antarctica: off Shag Rocks and South Georgia, off Coronation Island (the South Orkney Islands), off King George Island (the South Shetland Islands), off Deception Island, and off Joinville and Anvers Islands (Antarctic Peninsula). However, it was also collected off Cape Adare, in the Ross Sea, pointing to a Circum-Antarctic distribution of the species.

Figures

Figure 3. Antarctoscyphus asymmetricus Peña Cantero, García Carrascosa and Vervoort, 1997: (a) fragment of a lateral branch showing hydrothecal arrangement; (b) distal part of cauline internode showing axillary hydrotheca and origin of paired branches; (c) hydrocladial branching (note hydrotheca outside axil of branches); (d, e) hydrothecae (note extreme development of one abcauline cusp); (f, g) gonothecae; (h) detail of gonothecal aperture. Scale bars: 1 mm (a), 250 µm (b, f), 200 µm (g), 150 µm (d, e), 50 µm (h).