Scolanthus shrimp, 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 : 7-11

Scolanthus shrimp , sp. nov.

Figures 2–4 , table 1

MATERIAL: Holotype AMNH _ IZC 331456 ; Locality: Ireland, Whittard Canyon, 48°29.238′ N, 10°23.802′ W, collected 17 June 2014, by R / V Celtic Explorer , CE14009, event 31, gear ROV (1774 m). Material examined for comparison: Isoscolanthus janainae Brandão, Gusmão, Gomes, 2019 , MZUSP 2729 (10 specimens; paratypes); Locality: Brazil, Rio de Janeiro, 21°31′ S, 40°08′ W, collected 31 May 1987, by TAAF, Sta. 56, CB 96 (295–300 m). Edwardsianthus gilbertensis ( Carlgren, 1931) AMNH 3614 (one specimen); Locality: Guam, NW Pacific, det. ca. 2001 by M. Daly. AMNH 3614A (two slides); Locality: Guam, NW Pacific, det. ca. 2001 M. Daly. Edwardsia tuberculata AMNH 3616A (two slides); Locality: Bergen, Norway, det. ca. 2001 by M. Daly.

DIAGNOSIS: Scolanthus with large, single nemathybomes that protrude into epidermis. Basitrichs of nemathybomes 40.0–52.2 × 3.0– 4.2 µm. Thin, tightly adherent periderm. Retractor and parietal muscles well developed and of similar size. Retractor circumscribed, with easily recognizable pennon; parietal muscle large, trianguloid, relatively broad.

EXTERNAL ANATOMY (fig. 2): Specimen elongate, wider proximally than distally, 2.3–5.1 mm in diameter and 15 mm in height. Column dark beige with eight mesenterial insertion visible in live specimens; preserved specimen yellow with mesenterial insertion visible. Proximal end rounded, not externally differentiated from rest of column (fig. 2A–C); body divided in aboral end, scapus, scapulus, and capitulum (fig. 2A, B, D). Periderm thin, tightly adherent, not deciduous, covering column and nemathybomes from distal scapus to proximal end (fig. 2A–C). Nemathybomes single, conspicuous, irregularly scattered on entire body (fig. 2B, E), but forming eight rows more visible in distal column perhaps due to contraction (fig. 2D). Sixteen small tentacles, arranged in two cycles, presumably all of same size (fig. 2F); tentacle length to 1.5 mm; light orange in live specimen, white in preserved state.

INTERNAL ANATOMY AND HISTOLOGY (fig. 3): Epidermis of entire body covered by thin periderm and nemathybomes (fig. 3A). Nemathybomes simple, large, to 213.6 × 181.0 µm, into mesoglea, but always protruding into epidermis (fig. 3B, C); basitrichs visible on top of nemathybome (fig. 3C). Longitudinal muscles of the tentacles ectodermal. Physa without terminal pore. Actinopharynx short, occupying less than one-third of column length, highly folded. No differentiated siphonoglyph.

Mesenterial arrangement as typical for edwardsiids: eight macrocnemes span length of body, from distal column to midcolumn (fig. 3D, E); eight microcnemes only in distalmost column, at bases of tentacles (not shown). Retractor and parietal muscles both well developed, strong (fig. 3E, F). Retractor muscle of macrocnemes strong, circumscribed, with easily recognizable pennon (fig. 3F). Retractor with relatively numerous processes (12–16), tightly spaced, variable in height and degree of ramification, more branched at extremities, including large pennon (fig. 3F). Parietal muscle large, trianguloid, relatively broad, with longer, branched lamellae closer to body wall; central lamella same thickness as side branches (fig. 3F). Specimen with oocytes, length 69.6–85.4 µm (fig. 3E); species inferred gonochoric.

CNIDOM (fig. 4): Spirocysts, basitrichs, p -mastigophores A. See figure 4 and table 1 for size and distribution.

DISTRIBUTION AND NATURAL HISTORY: Scolanthus shrimp , sp. nov., is known only from its type locality in the Whittard Canyon approximately 400 km off the coast of Ireland in the Celtic Sea, North Atlantic, at 1774 m depth .

ETYMOLOGY: The specific name “shrimp” honors the Science Research Mentoring Program (SRMP) at the AMNH and their high school students known informally as srmpers. The SRMP supported C.Q., S.L.B., and L.C.G. The species epithet is a noun in apposition.

REMARKS: Though the description of Scolanthus shrimp is based on a single specimen, the specimen was well preserved and all external and internal characters were easily described.

Figures

FIG. 2. External anatomy of Scolanthus shrimp. A, lateral view of live holotype; B, lateral view of preserved holotype showing nemathybomes arranged in rows on scapus; C, aboral view of the holotype showing nemathybomes on proximal end; D, detail of distal scapus with nemathybomes scarcely present distributed in rows; E, detail of nemathybomes on column; F, oral view of holotype with oral disc and 16 tentacles. Scale bars: A, E, 1 mm; B, 5 mm; C, 3.5 mm; D, 2.5 mm; F, 2 mm.

FIG. 3. Internal anatomy and microanatomy of Scolanthus shrimp. A, detail of periderm and nemathybomes on scapus; B, Nemathybome on scapus; C, detail of nemathybome with basitrichs inside (arrow); D, cross section through midcolumn showing mesenterial arrangement of eight macrocnemes (indicated by numbers); E, histological cross section through midcolumn showing mesenterial arrangement; F, detail of macrocneme in cross section showing circumscribed retractor with pennon (indicated by asterisk) and strong parietal muscle. Abbreviations: gt, gametogenic tissue. Scale bars: A, 0.2 mm; B, 0.4 mm C, D, 0.1 mm; E, 2 mm; F, 0.5 mm.

FIG. 4. Cnidom of Scolanthus shrimp. A, D–G, basitrich; B, gracile spirocyst; C, robust spirocyst.

Tables

TABLE 1. Cnidom of Scolanthus shrimp, sp. nov., and Scolanthus celticus, sp. nov. P-mast, p-mastigophores; S, proportion of specimens in which each cnidae was found; N, Total number of capsules measured; F, frequency; +++, very common; ++, common; +, rather common; *, rare.

Tissue/categories	Scolanthus shrimp , sp. nov.						Scolanthus celticus , sp. nov.
	fig. 4	Range of length and width of capsules (µm)	± SD	N	S	F	fig. 7	Range of length and width of capsules (µm)	± SD	N	S	F
NEMATHYBOMES
Basitrichs	(A)	41.7–58.4x 3.3–4.6	51.8±3.9 x 3.9±0.3	48	1/1	++	(A)	42.0–58.4 x 3.8–5.6	48.3±3.5 x 4.6±0.4	36	2/2	++
TENTACLES
Spirocysts	(B–C)	14.4–32.8 x 2.8–7.6	24.1±4.1 x 4.6±0.9	108	1/1	+++	(B–C)	15.6–42.2 x 3.1–8.3	29.6±5.5 x 5.0 ±1.1	177	2/2	+++
Basitrichs	(D)	22.4–37.3 x 2.9–4.2	27.4±2.5 x 3.5±0.3	58	1/1	++	(D)	27.2–35.6 x 2.2–4.2	31.0±1.7 x 3.5±0.3	100	2/2	+++
PHARYNX
Basitrichs I		—	—				(E)	14.2 x 3.2	—	1	1/2	*
Basitrichs II	(E)	32.4–40.1 x 2.8–3.9	35.2±1.0 x 3.3±0.4	51	1/1	++	(F)	28.3–34.1 x 3.0–3.9	30.8±1.9 x 3.5±0.3	42	2/2	+++
FILAMENT
Basitrichs I	(F)	17.6–25.8 x 2.0–2.9	21.9±2.2 x 2.4±0.2	59	1/1	++	(G)	19.2–30.9 x 1.9–3.5	23.6±2.3 x 2.5±0.3.	78	2/2	++
Basitrichs II	(G)	39.0–51.9 x 3.2–4.7	44.6±3.0 x 3.8±0.3	47	1/1	+++	(H)	38.8–54.1 x 2.1–4.7	48.0±2.9 x 3.9±0.4	110	2/2	+++
P -mast A		—	—				(I)	25.0–32.0 x 5.0–6.5	28.9±1.8 x 5.8±0.4	26	2/2	+