Scolanthus celticus, Gusmão & Qu & Burke & Rodríguez, 2020

Gusmão, Luciana C., Qu, Cherie, Burke, Sadie L. & Rodríguez, Estefanía, 2020, Two new deep-sea species of burrowing anemones (Cnidaria: Actiniaria: Edwardsiidae) from Whittard Canyon off the southwestern coast of Ireland, American Museum Novitates 2020 (3945), pp. 1-25 : 11-12

Scolanthus celticus , sp. nov.

Figures 5–7 , table 1

MATERIAL: Holotype AMNH _ IZC 331453 ; Locality: Ireland, Whittard Canyon, 48°42.534′ N, 10°33.642′ W, collected 11 June 2014, by R / V Celtic Explorer, CE 14009, event 9, gear ROV (1130 m). Paratypes AMNH _ IZC 331454 (2 specimens), sampled at the same site of the holotype. Additional material. AMNH _ IZC 331455 (1 specimen), sampled at the same site of the holotype. Material examined for comparison: Scolanthus crypticus Brandão, Gusmão, Gomes, 2019 , MNRJ 8685 (8 specimens; paratypes); Locality : Brazil, São Paulo, offshore Ubatuba , 23°34′ S, 44°48′ W, collected 22 October 1986 (40 m) .

DIAGNOSIS: Scolanthus with nemathybomes single or clustered, largely sunken into mesoglea protruding only a little in epidermis. Periderm very thick, rusty brown, deciduous. Basitrichs of nemathybomes 42.0–58.4 × 3.8–5.6 µm. Retractor strong, elongated, diffuse-circumscribed, with numerous processes (23–33) and easily recognizable pennon. Parietal muscle small, ovoid, and much smaller than retractor muscle. With p -mastigophores A in filament.

EXTERNAL ANATOMY (fig. 5): All specimens elongate but stout, robust, wider proximally than distally, 5–10 mm in diameter, and 14–24 mm in height. Proximal end rounded, externally differentiated from rest of column but not true physa (fig. 5A, B); body divided in aboral end, scapus, scapulus, and capitulum. All preserved specimens with distal column and oral disc retracted, including part of scapus, scapulus, and capitulum; tentacles not visible (fig. 5A). Periderm thick, rusty brown, tightly adherent, deciduous, covering column and nemathybomes from distal scapus to proximal end (fig. 5A, B). Nemathybomes conspicuous, irregularly scattered on body (fig. 5B, C), single or compound, more aggregated on proximal end (fig. 5B) due to contraction of body. Sixteen small tentacles, arranged in two cycles, presumably all of same size; tentacle length to 3 mm.

INTERNAL ANATOMY AND HISTOLOGY (fig. 6): Epidermis of entire body covered by thick periderm and nemathybomes (fig. 6A, E). Nemathybomes large, to 247.0 × 146.6 µm, simple or compound, sunken into mesoglea, but protruding into epidermis (fig. 6B, C). Longitudinal muscles of tentacles ectodermal (fig. 6D). Physa not histologically differentiated from scapus; without terminal pore. Actinopharynx short, up to 1.5 mm, occupying less than one-third of body length, highly folded. No differentiated siphonoglyph.

Mesenterial arrangement as typical for edwardsiids: eight macrocnemes span length of body, from distal column (fig. 6E) to midcolumn (fig. 6F, G); eight microcnemes only in distalmost column, at bases of tentacles (not shown). Retractor and parietal muscles both well developed, strong (fig. 6F, H). Retractor muscle of macrocnemes strong, circumscribed to somewhat diffuse, with easily recognizable pennon (fig. 6H). Retractor with numerous processes (23–33), tightly spaced, variable in height and degree of ramification, more branched at the pennon (fig. 6H). Parietal muscle small, weak, trianguloid, with longer, branched lamellae closer to body wall; central lamella thicker than side branches (fig. 6I). Specimens examined (holotype and paratype AMNH_IZC 331454) with spermatic cysts (fig. 6J), length 45.2–114.3 µm; species inferred to be gonochoric.

CNIDOM (fig. 7): Spirocysts, basitrichs, p -mastigophores A. See figure 7 and table 1 for size and distribution.

DISTRIBUTION AND NATURAL HISTORY: The four specimens were collected in a single collection site in the Whittard Canyon approximately 450 Km from the SW coast of Ireland, North Atlantic, at 1130 m depth. Scolanthus celticus was collected less than 30 km from the type locality of S. shrimp , suggesting a pattern of sympatry common among edwardsiids ( Daly and Ljubenkov, 2008).

ETYMOLOGY: The specific name celticus honors the Celtic Explorer, a multipurpose research vessel operated by the Marine Institute in Galway, Ireland, which collected specimens of the new species.

Figures

FIG. 5. External anatomy of Scolanthus celticus. A, lateral view of live holotype; B, lateral view of preserved holotype showing thick periderm on scapus; C, Oral view of proximal end with periderm and nemathybomes; D, Detail of nemathybomes on proximal scapus. Scale bars: A, 10 mm; B, 6 mm; C–D, 3.8 mm.

FIG. 6. Internal anatomy and microanatomy of Scolanthus celticus. A, detail of periderm on distal column; B, Simple nemathybome on midcolumn; C, detail of three nemathybomes protruding into epidermis; D, longitudinal muscle of tentacles ectodermal; E, eight parietal muscles indicating eight macrocnemes on distal column (retractors missing); F, cross-section through distal column showing eight macrocnemes; note 16 tentacles in cross-section; G, cross section through midcolumn below actinopharynx showing eight macrocnemes; H, detail of retractor muscle; pennon indicated by asterisk; I, detail of parietal muscle on distal column; J, spermatic cysts. Scale bar: A, 0.35 mm; B–D,F,J, 0.25 mm; E, 1.3 mm; G, 3.2 mm; H, 1.35 mm; I, 0.28 mm.

FIG. 7. Cnidom of Scolanthus celticus. A, D–H, basitrich; B, gracile spirocyst; C, robust spirocyst; I, p-mastigophore A.