Symplectoscyphus weddelli, Peña Cantero, 2002

Peña Cantero, A. L., 2002, Species of Symplectoscyphus Marktanner-Turneretscher, 1890 (Cnidaria: Hydrozoa, Sertulariidae) from recent Antarctic expeditions with R. V. Polarstern, with the description of four new species, Journal of Natural History 36, pp. 1509-1568 : 1560-1562

Symplectoscyphus weddelli sp. nov.

(gure 16; table 15)

Material examined. ANT VIII-5 Stn 16-399, numerous stems on polychaete tubes and a mass of stems ca 40 mm diameter (RMNH-Coel. 29 210, slide 4855); ANT VIII-5 Stn 16-407, a mass of stems ca 15 mm diameter and numerous stems up to 25 mm on Billardia subrufa (Jäderholm, 1904) , with gonothecae (holotype, RMNH-Coel. 29 211, three slides 4856, part of type series); ANT VIII-5 Stn 16-475, a mass of stems and branches, some incipient stems on hydrocoral and polychaete tubes (RMNH-Coel. 29 212, slide 4857); ANT VIII-5 Stn 16-486, a mass of stems ca 20 mm diameter, with gonothecae (RMNH-Coel. 29 213, slide 4858); ANT IX-3 Stn 220, a colony with a few unbranched stems up to 6 mm high on uncalci ed Bryozoa (RMNH-Coel. 29 214, slide 4859) .

Description. Colonies with monosiphonic stems up to 25 mm high, arising from stolonal hydrorhiza. Branching irregular and in several planes. Branches originating laterally at hydrothecal base; plane formed by hydrothecae of lower-order branch perpendicular to that formed by hydrothecae of previous branch. Occasionally branches becoming anastomosing stolons distally.

Stems divided into more or less straight internodes with oblique nodes sloping in alternate directions (gure 16A, B); one hydrotheca per internode. Hydrothecae abcaudally directed, with indistinct in exion point where the adcauline wall becomes free (gure 16A–E). Adcauline hydrothecal wall adnate to internode for approximately half its length, though usually adnate part slightly longer than free portion. Free part of adcauline hydrothecal wall straight or slightly convex. Abcauline hydrothecal wall slightly concave. Cusps of hydrothecal aperture sharp and separated by deep embayments (gure 16A–E). Rim of hydrothecal aperture with frequent renovations.

Gonothecae ovoid, inserting at hydrothecal base. Gonothecal walls spirally folded, forming a frill with eight or nine turns (gure 16F). Gonotheca distally with a long, funnel-shaped neck bearing the gonothecal aperture. The material from ANT 2014

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VIII- 5 Stn 16-486 has slightly diVerent gonothecae (gure 16G): they are provided with a pattern of ca 12 rings and distally have a short, funnel-shaped neck.

Remarks. We believe that the diVerences in shape of the gonothecae between the colonies from ANT VIII- 5 Stn 16-486 and the remaining material are due to sexual dimorphism, though speci c diVerences cannot be ruled out. The study of more material could clarify this question.

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Symplectoscyhus weddelli sp. nov. belongs to the group of Antarctic species having gonothecae provided with a pattern of rings ( S. cumberlandicus , S. curvatus , S. exochus , S. nesioticus , S. so ae sp. nov. and S. vanhoe V eni). It diVers from S. cumberlandicus and S. so ae sp. nov. mainly in having monosiphonic rather than polysiphonic colonies, but also because the hydrothecal shape and size are diVerent. From S. curvatus it distinctly diVers in shape and size of the hydrothecae, as that species has much more robust colonies and the hydrotheca is cylindrical and much larger. The colony form diVers from that of S. nesioticus , in which the internodes are markedly arranged in zigzag fashion. Moreover, the hydrothecae in S. nesioticus are free for almost the whole adcauline length and have a completely diVerent shape.

Symplectoscyphus weddelli sp. nov. is closest to S. vanhoe V eni and S. exochus , though it diVers from these in the shape of the hydrothecae. In S. vanhoe V eni the hydrothecae are more robust and the cusps of the hydrothecal aperture are blunt and separated by shallow embayments. In S. exochus the hydrothecae are adnate to the internode for more than half the adcauline wall, there is a marked in exion point where the adcauline wall becomes free, and the hydrothecal cusps are blunt and separated by shallow embayments. Moreover, the hydrothecae are distinctly smaller.

Ecology and distribution. Symplectoscyphu s weddelli sp. nov. has been collected at depths from 119 to 390 m, on muddy and rocky bottoms. It has been found growing on uncalcifed Bryozoa, polychaete tubes and Hydrozoa [ Billardia subrufa (Jäderholm, 1904) ]. It is used as substratum by other hydroids ( Filellum sp. ). Fertile colonies of Symplectoscyphus weddelli sp. nov. were collected in January and February.

Symplectoscyphu s weddelli occurs along the south and east coasts of the Weddell Sea (oV Ronne Ice Shelf, McDonald Ice Rumples, Riiser-Larsen Ice Shelf and Atka Iceport).