Actinostola crassicornis (Hertwig, 1882)

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 : 44-46

Actinostola crassicornis (Hertwig, 1882)

( Figs. 14 , 23–24 ; Table 10; Appx. 1, 2)

Dysactis crassicornis Hertwig, 1882a , b; Hertwig 1888; McMurrich 1893.

Actinostola crassicornis: Carlgren 1927 ; Carlgren 1949; Riemann-Zürneck 1978a.

Actinostola excelsa McMurrich, 1893 ; Riemann-Zürneck 1978b.

Actinostola pergamentacea McMurrich, 1893 ; Riemann-Zürneck 1978a.

? Actinostola intermedia Carlgren, 1899 ; Carlgren 1927; Carlgren 1949.

non Actinostola crassicornis: Fautin 1984 .

MATERIAL EXAMINED

Polarstern ANT XIX/5 : stn. PS61/150 (AMNH-4704, 2 specimens); stn. PS61/153 (AMNH-4698, 3 specimens) .

COMPARATIVE MATERIAL EXAMINED

Dysactis crassicornis (Hertwig, 1882) . SMNH-Type-1183. Holotype. “ Leg. Challenger, st. 313; 52ºS 68ºW, 55 fm”. Also labelled as Actinostola (Dysactis) crassicornis (Hertwig, 1882) .

Actinostola intermedia Carlgren, 1899 . SMNH-Type-1184. Holotype. “ The Strait of Magellaen , Cap. Vicente, 150 m. Dead shell and stone bottom, Leg. ¿?”.

DIAGNOSIS

Pedal disc well developed, flat, to 45 mm diameter. Column smooth, tough, cylindrical or funnel-shaped, slightly wider distally than proximally, to 43 mm diameter and 60 mm height in preserved specimens, not divisible into regions. Oral disc very wide, flat, to 70 mm diameter. Living specimens with white column; tentacles and oral disc with irregular dark red spots; preserved specimens retain red colour of oral disc and tentacles. Tentacles to 190, restricted to column margin, inner longer than outer ones. Marginal sphincter muscle mesogleal, very weak, diffuse and long. More mesenteries proximally than distally. Mesenteries thin, arranged in five cycles; first and second cycles perfect and sterile, rest imperfect and fertile; fourth and fifth cycles arranged according to the Actinostola rule (mesenteries of pair developed unequally; one facing the precedent cycle more developed). Retractor muscles weak, diffuse; parietobasilar muscles poorly developed. Longitudinal muscles of tentacles mesogleal. Juveniles internally brooded in coelenteron. Cnidom: Spirocysts, basitrichs, and microbasic b - and p -mastigophores. Relatively large microbasic b -mastigophores in base of outer tentacles, to 56 µm long; mesenterial filaments with basitrichs. For a complete description of Actinostola crassicornis , see Riemann-Zürneck (1978a).

GEOGRAPHIC AND BATHYMETRIC DISTRIBUTION

Actinostola crassicornis was originally described by Hertwig (1882a, b; 1888) in the southeastern coast of Chile. Subsequently, the geographic range of the species was extended to the southwestern coast of Argentina (McMurrrich 1893; Carlgren 1927; Riemann-Zürneck 1978a). The material from this study considered as A. crassicornis , has been collected in the sub-Antarctic region, in the northern branch of the Scotia Arc , east of Burdwood Bank, between 277–296 m depth, a region that encompasses the distribution described by Riemann- Zürneck (1978a) for A. crassicornis .

Actinostola crassicornis is distributed in the southwestern Atlantic and the sub-Antarctic region, in continental shelf and bathyal depths ( Fig. 14f ).

REMARKS

Austral species within the genus Actinostola are very difficult to distinguish based on traditional morphological characters (Riemann-Zürneck 1978a; Häussermann 2004). Fautin (1984) synonymized five austral species of Actinostola as A. crassicornis ( A. excelsa , A. pergamentacea , A. intermedia Carlgren, 1899 , A. chilensis McMurrich, 1904 , and A. clubbi Carlgren, 1927 ) and identified the Antarctic specimens of the genus that she studied as A. crassicornis ( Fautin 1984) . However, the specimens studied by Fautin are the only ones of A. crassicornis in Antarctic waters. The material of Fautin’s (1984) study needs to be re-examined to confirm her conclusions. We consider here A. crassicornis sensu Riemann-Zürneck (1978a) . This species has a smooth but tough column with short and tough tentacles, and its geographic distribution only reaches sea floors north of the Polar Front. Furthermore, we consider here the identity of A. intermedia and A. clubbi dubious until further revision. The present study suggests that none of the arguments provided by previous authors (e.g. cnidae, number of tentacles and mesenteries, etc. see Riemann-Zürneck 1978a; Fautin 1984; Häussermann 2004) to establish identities or synonymies of these species are robust.

Figures

FIGURE 14. Distribution map of species. a) Isotealia antarctica Carlgren, 1899. b) Capnea georgiana (Carlgren, 1927). c) Stephanthus antarcticus Rodríguez & López-González, 2003. d) Liponema multiporum Hertwig, 1882. e) Dactylanthus antarcticus (Clubb, 1908). f) Actinostola crassicornis (Hertwig, 1882). Green triangles, type locality; green circles, previous localities; red circles, localities from this study; yellow circles, localities from this study from underwater photography survey; dark line, Subtropical Front; light line, Polar Front.

FIGURE 23. External anatomy of Actinostola crassicornis (Hertwig, 1882). a) Oral view of living specimen [AMNH-4704]. b) View of the pedal disc and distal margin of the column of living specimen [AMNH-4704]. c–d) Lateral view of preserved specimen [AMNH-4698]. Scale bars: a–d, 30 mm.

FIGURE 24. Cnidae of Actinostola crassicornis (Hertwig, 1882). a, b, d, g, i) Basitrichs. c) Spirocyst. e, h, j, k) Microbasic p- mastigophores. f) Microbasic b-mastigophore.