Actinoscyphia saginata ( Verrill, 1882 )

Gusmão, Luciana C. & Rodríguez, Estefanía, 2021, Deep-Sea Anemones (Cnidaria: Anthozoa: Actiniaria) From The South Atlantic, Bulletin of the American Museum of Natural History 2021 (444), pp. 1-73 : 27-30

Actinoscyphia saginata ( Verrill, 1882)

Figures 11–12, table 5

MATERIAL: MNRJ 4223 (1 specimen) ; locality: REVIZEE Bahia 2, Sta. ZO 522, sector 2, dredging 58, Southwestern Atlantic , Brazil, off the coast of Espirito Santo ( ES), 21°15.22′ S 39°53.05′ W, collected on 8 July 2000 by R / V Thalassa (1694 m) . MNRJ 4224 (1 specimen) ; locality: REVIZEE Bahia 2, Sta. ZO 527, sector 1, dredging 33, Southwestern Atlantic , Brazil, off the coast of Espirito Santo ( ES), 20°02.23′ S 39°23.62′ W, collected on 29 June 2000 by R / V Thalassa (1402 m) . MNRJ 4226 (1 specimen) ; locality: REVIZEE Bahia 2, Sta. EO 525, sector 1, dredging 31, Southwestern Atlantic , Brazil, off the coast of Espirito Santo ( ES), 20°10.42′ S 38°40.42′ W, collected on 28 June 2000 by R / V Thalassa (1639 m) .

MATERIAL EXAMINED: Actinoscyphia saginata: ZMUC ANT-000014 (1 specimen; syntype) ; locality: Ingolf Expedition, Sta. ING032, Arctic Ocean, Davis Strait , 66°35.0′S 56°38.0′W, collected 11 July 1896 (599 m). USNM 78477 (3 specimens) ; locality: Northern Gulf of Mexico Continental Slope Expedition ( NGOMCS), Cruise, IV, Sta. WC-9, R / V Citation, North Atlantic Ocean , northern Gulf of Mexico off Louisiana, 27°42.79′ S 91°15.28′ W, collected on 23 May 1985 (695–807 m). USNM 079597 (1 specimen) ; locality: northern Gulf of Mexico Continental Slope Expedition ( NGOMCS), Cruise, III, Sta. C 11, R / V Gyre , northern Gulf of Mexico off Louisiana, 27°13.69′ S 89°36.80′ W, collected on 8 December 1984 (2063–2085 m). Actinoscyphia plebeia: AMNH 4080 (14 specimens) ; locality: ANT XIX/3 Cruise, ANDEEP I Program, R / V Polarstern, Sta. PS 61/114-10, Southern Ocean, Drake Passage, 61°43.7′ S 60°42.62′ W, collected on 19 February 2002 by Mercedes Conradi (2853–2856 m) .

EXTERNAL ANATOMY (fig. 11): Animal irregularly shaped (fig. 11A). Pedal disc well developed, elongate, perpendicular to directive axis, tubular, wrapped around cylindrical substrate, with golden-brown chitinous material (fig. 11A, B); 88–142 mm in diameter in preserved specimens. Column irregularly shaped, not divisible into regions, stiff, smooth, mostly without epidermis and light-pink mesoglea exposed (fig. 11A); 19–57 mm in length and 52–92 mm in preserved specimens. Brown-red epidermis in parts of column (fig. 11A) and oral disc. Oral disc wide, irregularly shaped, folding on itself, but not bilobed (fig. 11A), with large central mouth; 34–62 mm in diameter in preserved specimens. Tentacles brown-red, slender, long, marginal, with beige, mesogleal basal aboral thickenings (fig. 11A); 140–152 in two marginal cycles (fig. 11A); outer tentacles longer than inner ones, longest tentacle up to 25 mm in preserved specimens.

INTERNAL ANATOMY AND HISTOLOGY (fig. 11): Body wall thick throughout column with mesoglea (306–526 μm) much thicker than gastrodermis (60–172 μm), and epidermis (69–237 μm); mesoglea less thick proximally. Marginal sphincter musculature mesogleal, weak and diffuse without tendency for stratification, wider marginally and thinner proximally closer to gastrodermis (fig. 11C): all alveoli nonpigmented, larger and reticular distally (fig. 11D), smaller and scattered proximally (fig. 11E). Longitudinal musculature of tentacles ectodermal but less developed in aboral side (fig. 11F); mesogleal basal aboral thickenings in tentacles (fig. 11G).

Mesenteries hexamerously arranged in five cycles (6+6+12+24+n = 72–80 pairs) on entire body length: mesenteries of first and second cycles perfect proximally (fig. 11H), including two pairs of directives each associated to one siphonoglyph. First cycle sterile; second to third cycles imperfect, fertile, with filaments only proximally (fig. 11H); fourth cycle imperfect, sterile, with filaments (fig. 11I); fifth cycle imperfect, sterile, without filaments (fig. 11J). Same number of mesenteries distally and proximally. Mesenteries thin, with some sections with mesogleal thickenings (fig. 11B, H); retractors diffuse slightly more developed distally (fig. 11I, L); well-developed parietobasilar musculature in all mesenteries (fig. 11M) less developed in mesenteries of fifth cycle (fig. 11N). All specimens collected in June and July males; major axis of spermatic cysts 76–238 μm (fig. 11K). Species inferred gonochoric.

CNIDOM (fig. 12): Spirocysts, basitrichs, p -mastigophores B1, and holotrichs. Some nematocysts found in the actinopharynx (fig. 12M) and filament (fig. 12P) are likely the result of contamination by feeding. See figure 12 and table 5 for size and distribution.

DISTRIBUTION AND NATURAL HISTORY: Actinoscyphia saginata was originally described from the Atlantic coast of the United States off New England (968 m) ( Verrill, 1882). The species is also known from the Atlantic coast of France (2108–2177 m) and Morocco (1341–1394 m) ( Riemann-Zürneck, 1978). Our specimens extend the geographic distribution of A. saginata to the South Atlantic off the coast of Espírito Santo, Brazil and falls within the known bathymetry for the species (1402–1694 m).

REMARKS: The genus Actinoscyphia contains five valid species that are easily recognized by their venus flytraplike morphology: large bilobed oral discs and marginal tentacles arranged in two cycles forming a concave surface. The morphology of the body and oral disc enables these anemones to position themselves within the current and and feed on particles upstream. Although the term “venus flytrap anemone” was originally used to refer to species in genus Actinoscyphia , some hormathiids in genera Phelliactis Simon, 1892 , and Paraphelliactis Carlgren, 1928b , as well as members of Amphianthus Hertwig, 1882 , also have bilobed oral discs with marginal tentacles resembling to the ones seen in actinoscyphiids. The similarity in the venus flytraplike morphology in all these genera has led to misidentification of the many images of venus flytrap anemones attributed to Actinoscyphia , when in fact they refer to other families and genera. In any case, species of Actinoscyphia are mainly distributed in the North Atlantic (A.