Hormosoma scotti Stephenson, 1918a

Rodríguez, Estefanía & López-González, Pablo J., 2013, <strong> New records of Antarctic and Sub-Antarctic sea anemones (Cnidaria, Anthozoa, Actiniaria and Corallimorpharia) from the Weddell Sea, Antarctic Peninsula, and Scotia Arc </ strong>, Zootaxa 3624 (1), pp. 1-100 : 51-55

Hormosoma scotti Stephenson, 1918a

( Figs. 27–30 ; Table 11; Appx. 1, 2)

non Actinia papaver Dana, 1846 ; Dana 1849; Milne-Edwards 1857; Dana 1859.

Paractis papaver: Clubb 1908 ; Pax 1926.

Hormosoma scotti Stephenson 1918a ; Pax 1926; Carlgren 1927; Carlgren 1928; Carlgren & Stephenson 1929; Carlgren 1949; Dunn 1983; Riemann-Zürneck 1990.

Hormosoma violaceum Pax, 1922 ; Pax 1923.

Actinostola rufostriata Pax, 1922 ; Pax 1923.

MATERIAL EXAMINED

Polarstern ANT XV/3: stn. PS48/154 (AMNH-4291, 3 specimens).

Polarstern ANT XVII/3 : stn. PS56/085-1 (AMNH-4601, 1 specimen; AMNH-4610, 7 specimens) .

Polarstern ANT XXI/2 : stn. PS65/039-1 (AMNH-4816, 1 specimen) ; stn. PS65/245-1 ( BEIM: ANT-4828, 1 specimen; AMNH-4862, 1 specimen); stn. PS65/276-1 ( BEIM: ANT-4978; 2 specimens) .

TABLE 11. Size ranges of the cnidae of Hormosoma scotti Stephenson, 1918 ; for comparative cnidae data of the species see Dunn (1983). Χ: mean. SD: standard deviation. S: ratio of number of specimens in which each cnidae was found to number of specimens examined. N: total number of capsules measured. F: Frequency, +++ = very common, ++ = common, + = rather common, --- = sporadic. Abbreviations: Mc, Microbasic. (*) Mean values based in fewer than 40 capsules.

DIAGNOSIS

Pedal disc well developed, flat, to 78 mm diameter, often with slight central protuberance. Column smooth, firm, thick, cylindrical or dome-shaped in contracted specimens, to 60 mm diameter and 40 mm height in preserved specimens, not divisible into regions but distal margin strong, often forming a collar; fosse well-developed; preserved specimens with corrugated column. Oral disc wide, flat, to 62 mm diameter, mesenterial insertions visible. Distinct chromatic pattern in living specimens: white column with irregular orange spots, oral disc light red or orange with dark orange radial lines coinciding with mesenterial insertions; tentacles light orange with more or less visible orange bands; mouth and actinopharynx light orange; preserved specimens reddish to orange depending on epidermis erosion. Tentacles relatively short and thick (to 9 and 8 mm, respectively), to 96, restricted to column margin, inner longer than outer ones. Marginal sphincter muscle mesogleal, strong, diffuse, concentrated in column margin. Equal number of mesenteries proximally and distally. Mesenteries arranged in four cycles; all perfect and fertile save fourth cycle (imperfect). Retractor muscles diffuse; parietobasilar muscles well developed, with thick mesogleal pennon. Longitudinal muscles of tentacles mesogleal, slightly more developed in oral side. Cnidom: Spirocysts, basitrichs, and microbasic b - and p -mastigophores. Large microbasic b -mastigophores in base of outer tentacles, to 76 µm long. For a complete description of Hormosoma scotti , see Dunn (1983).

GEOGRAPHIC AND BATHYMETRIC DISTRIBUTION

Hormosoma scotti has been previously collected in the area of Antarctic Peninsula, Scotia Sea and in McMurdo Sound (Ross Sea), between 16–769 m depth ( Dunn 1983).

The material from this study is from the eastern Weddell Sea, between 166–318 m depth, representing the first records for the species in the area.

Hormosoma scotti is a circumpolar endemic Antarctic species from continental shelf and bathyal depths ( Fig. 27b ).

REMARKS

We have examined additional material from the South Shetland Islands. However, we have not included this material here because of slight differences in column texture, fertility distribution, and cnidae that need to be checked further.

Genus Stomphia Gosse, 1859

Figures

FIGURE 27. Distribution map of species. a) Actinostola georgiana Carlgren, 1927. b) Hormosoma scotti Stephenson, 1918. c) Stomphia selaginella (Stephenson, 1918). d) Galatheanthemum profundale Carlgren, 1956. e) Actinoscyphia plebeia (McMurrich, 1893). f) Eltaninactis infundibulum Dunn, 1983. Green triangles, type locality; green circles, previous localities; red circles, localities from this study; dark line, Subtropical Front; light line, Polar Front.

FIGURE 28. External anatomy of Hormosoma scotti Stephenson, 1918. a) Oral view of living and expanded specimen [BEIM(ANT-4828)]. b) Lateral-oral view of semi-contracted living specimen [AMNH-4816]. c–d) Lateral and oral view of contracted living specimen [AMNH-4816]. Scale bars: a, 25 mm; b–d, 30 mm.

FIGURE 29. External anatomy of Hormosoma scotti Stephenson, 1918. a) Oral view of preserved specimen [AMNH-4291]. b–c) Lateral view of preserved specimens [BEIM(ANT-4978)], [BEIM(ANT-4828)]. d) Detail of the distal margin of the column showing the ring formed by the marginal sphincter muscle. e–f) Oral view and pedal disc of preserved specimen [BEIM(ANT-4828)]. Scale bars: a, e, 25 mm; b, d, 15 mm; c, 20 mm; f, 30 mm.

FIGURE 30. Cnidae of Hormosoma scotti Stephenson, 1918. a, c, e, h) Spirocysts. b, d) Basitrich.s f, g) Microbasic b- mastigophores. i, j, k) Microbasic p-mastigophores.