Actinoscyphia plebeia ( McMurrich, 1893 )

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 : 63-67

Actinoscyphia plebeia ( McMurrich, 1893)

( Figs. 27 , 35–36 ; Table 14; Appx. 1, 2)

Actinernus plebeius McMurrich, 1893 : Doumenc 1975.

Actinoscyphia plebeia: Stephenson 1920a ; Carlgren 1949; Doumenc 1975; Riemann-Zürneck 1978b; Fautin 1984. Actinoscyphia groendyki Eash-Loucks & Fautin, 2012 (part.)

MATERIAL EXAMINED

Polarstern ANT XIX/3 : stn. PS61/114-10 (AMNH-4080, 65 specimens; BEIM: ANT-4081, 4 specimens) .

DIAGNOSIS

Pedal disc well developed, elongated perpendicular to directives axis, often rapping tubes of worms or gorgonians, to 48 mm diameter, often with rest of chitinous material. Column smooth, firm, fan-shaped, to 59 mm diameter and 47 mm height in preserved specimens, not divisible into scapus and scapulus. Oral disc not lobed but very wide, to 60 mm diameter, often folding on itself (in axis perpendicular to pedal disc). Living specimens with whitish to light pink column, becoming light orange distally; tentacles light orange; oral disc and actinopharynx dark red; preserved specimens with whitish column, only actinopharynx retains red colour. Tentacles short, to 154, restricted to column margin, inner shorter than outer ones; tentacles with slight mesogleal thickenings in base. Marginal sphincter muscle mesogleal, weak and diffuse. Equal numbers of mesenteries proximally and distally. Mesenteries thin, arranged in five cycles, only first cycle perfect and sterile, rest imperfect and fertile. Retractor muscles weak, diffuse and short; parietobasilar muscles well developed. No acontia. Cnidom: Spirocysts, basitrichs, holotrichs, and microbasic p -amastigophores. For a complete description of Actinoscyphia plebeia , see McMurrich (1893) and Fautin (1984).

TABLE 14. Size ranges of the cnidae of Actinoscyphia plebeia (McMurrich, 1983) ; 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.

GEOGRAPHIC AND BATHYMETRIC DISTRIBUTION

Actinoscyphia plebeia is distributed in the Antarctic region, in the Ross Sea, and the Drake Passage, between 600– 4,000 m depth; however, its type locality is in the northern Pacific limit of the sub-Antarctic region, in the southern coast of Chile ( McMurrich 1893; Fautin 1984).

The material from this study confirms the presence of this species in the Drake Passage, between 2,852–2,856 m depth. Actinoscyphia plebeia is an Antarctic and sub-Antarctic species, inhabiting bathyal depths, and occasionally present in Antarctic continental shelves ( Fig. 27e ).

REMARKS

According to Eash-Loucks and Fautin (2012), Actinoscyphia groendyki Eash-Loucks & Fautin, 2012 from deep waters in the northeastern Pacific differs from the holotype of A. plebeia in the number of mesenteries and tentacles, length and shape of the marginal sphincter muscle, mesogleal thickness, and cnidae. Furthermore, these authors synonymised the Antarctic specimens reported by Fautin (1984) as A. plebeia with A. groendyki , extending the distribution of the latter species to Antarctica.

The specimens of Actinoscyphia in this study show a continuum of variation of the marginal sphincter muscle, thickness of mesoglea, and cnidae between those reported for A. groendyki and A. plebeia . Our specimens are from the Drake Passage, a locality close to that of Fautin’s (1984) specimens. In our opinion, the differences provided by Eash-Loucks and Fautin (2012) to distinguish A. groendyki from the holotype of A. plebeia are attributable to intraspecific variability and preservation artifacts of a sole deep-sea specimen. Moreover, the geographic distribution proposed by Eash-Loucks and Fautin (2012) seems unlikely: Actinoscyphia groendyki is cited as occurring in the northeastern Pacific and around Antarctica, but A. plebeia is reported only from the southern coast of Chile. Until further molecular revision, we rather consider two species, A. plebeia distributed in Antarctica and sub-Antarctica, and A. groendyki in the northeastern Pacific.

Family ISANTHIDAE Carlgren, 1938

Genus Eltaninactis Dunn, 1983

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 35. External anatomy of Actinoscyphia plebeia (McMurrich, 1893). a) Living specimens [AMNH-4080]. b) Lateral view of preserved specimen [AMNH-4080]. c) View of distal margin folded and covering the oral disc in a preserved specimen [AMNH-4080]. d) Lateral view of preserved specimen showing the modified pedal disc anchored to a polychaete tube [AMNH-4080]. e) Detail of the modified pedal disc wrapping a polychaete tube. f) View of the oral disc of a semi-contracted preserved specimen [AMNM-4080]. g) View of distal margin folded and covering the oral disc in a preserved specimen [AMNH-4080]. Scale bars: a, 30 mm; b, d, f–g, 15 mm; c, e, 20 mm.

FIGURE 36. Cnidae of Actinoscyphia plebeia (McMurrich, 1893). a, b, d, g, h, j, l) Basitrichs. c, e, f) Spirocysts. i) Holotrich. k, m) Microbasic p-amastigophores.