Sicyonis careyi, Fautin, 2012

Fautin, D. G., 2012, Taxonomy and distribution of sea anemones (Cnidaria: Actiniaria and Corallimorpharia) from deep water of the northeastern Pacific, Zootaxa 3375, pp. 1-80 : 26-29

Sicyonis careyi n. sp.

( Figures 18–21, Table 4, Appendix 8)

Body form and size. Column of specimens white to light grey (color of exposed mesoglea). Stiff due to thick mesoglea (to 6 mm mid-column in specimen 39 mm long); smooth except for few shallow irregular furrows; mesenterial insertions rarely visible. Cylindrical column of preserved specimens may be slightly compressed laterally (likely due to compression in collecting net), tentacles partially hidden in all specimens examined. Oral and pedal disc approximately same diameter, or column may taper slightly from oral to pedal disc ( Figure 18). Column of most specimens examined 33–56 mm long, shortest 10 mm long.

Pedal disc. Pinkish brown; smooth but rare furrows may mark insertions of mesenteries toward periphery. Typically 24–42 mm diameter (7 mm diameter in smallest specimen); concave, concavity reaching 16 mm long; typically grasping bolus of mud.

Oral disc and tentacles. Tan or brown, radially furrowed where mesenteries insert; hidden by tentacles and contracted column in all specimens examined. Diameter 34–48 mm (13 mm in smallest), roughly same diameter as column length. Mouth about 1/3 diameter of oral disc, same color as oral disc; two large white siphonoglyphs apparent.

Tentacles tan, circumferentially furrowed, slightly thickened aborally at base ( Figure 19a); arrayed in 3 cycles, about 80 in number (58 in smallest specimen). Inner tentacles endocoelic and larger than outer (exocoelic); short, pointed, 2–8 mm long, taper from 2–4 mm at base to 0.5–1 mm at tip. Small pore at tip ( Figure 19b) more apparent in endocoelic than exocoelic tentacles.

Internal anatomy. Actinopharynx tan, brown, or grey, long, longitudinally sulcate. Each of two deep, white siphonoglyphs attached to pair of directive mesenteries.

Mesenteries thin and numerous (about 80 pairs), irregularly arrayed; incomplete ones loosely follow Actinostola rule. Mesenteries of youngest cycle very thin and weak, exist only at extreme proximal end; lack filaments and musculature, possess gametogenic tissue ( Figure 19c). All other mesenteries muscular with filaments and large mesogleal thickenings distally ( Figure 19d). Mesenteries of second youngest cycle (typically 20 pairs) extend from pedal to oral disc but very small compared to those of older cycles; rarely possess gametogenic tissue. Oldest mesenteries (typically 20 pairs) sterile and long; most complete, although only one member or rarely both members of pair incomplete; contain oral but no marginal stomata.

Muscular mesenteries possess long, diffuse retractor muscles. Parietobasilar muscles weak, pennons lacking.

Mesogleal marginal sphincter muscle weak and moderately long; lies against endoderm ( Figure 19e), may be longitudinally striated distally. Occupies less than half column width distally, where alveoli large and loosely arrayed; tapers proximally, where more reticular toward endoderm, alveolar toward ectoderm.

Longitudinal musculature of tentacles mesogleal and well developed ( Figure 19a).

Cnidae. Spirocysts, basitrichs, holotrichs, microbasic p -mastigophores. Sizes and distribution of cnidae given in Table 4; cnidae illustrated in Figure 20.

Type specimens. Holotype: SBMNH 422541 , collected 18-Feb-1971 from 45.31° N 126.53° W, 2,750 m. Column length 39 mm, diameter of contracted distal end 46 mm, diameter of contracted proximal end 33 mm. 72 mesenteries span entire length of column and equal number gametogenic mesenteries exist only at proximal end; 72 tentacles.

Paratypes: KUIZ 003349 , 3 specimens, collected 18-Feb-1971 from 45.31° N 126.53° W, 2,750 m ; CAS 184530 , 1 specimen, collected 16-Mar-1970 from 44.63° N 125.67° W, 2,816 m ; RBCM 010-00572 - 001 , 1 specimen, collected 16-Mar-1970 from 44.63° N 125.67° W, 2,816 m ; USNM 1149363 , 1 specimen, collected 16- Mar-1970 from 44.63° N 125.67° W, 2,816 m ; SBMNH 149660 , 2 specimens, collected 16-Mar-1970 from 44.63° N 125.67° W, 2,816 m .

Etymology. Named in honor of Andrew G. Carey, Jr. who collected specimens of this species, as well as many other deep-sea anemones, off the coast of Oregon.

Distribution. Sicyonis careyi n. sp. appears endemic to the northeastern Pacific, where it occurs from 550 to 3,700 m ( Figure 21). No other member of the genus is known from the northeastern Pacific.

Taxonomic remarks. The genera Parasicyonis Carlgren, 1921 , and Synsicyonis Carlgren, 1921 , are so similar

In both Synsicyonis and Sicyonis , mesenteries of the last cycle are fertile and lack filaments; the last cycle occurs only at the extreme distal end of the column in members of Synsicyonis and at the extreme proximal end of the column in members of Sicyonis . The only species of Synsicyonis , S. elongata ( Hertwig, 1888) , is known from the middle of the North Pacific at 5,304 m; mesenteries of its youngest cycle are muscular.

Mesenteries of the youngest cycle are fertile in members of Parasicyonis and Sicyonis ; however, those of Parasicyonis possess mesenterial filaments, and those of Sicyonis lack mesenterial filaments. No species of Parasicyonis have been recorded from the Pacific Ocean.

In describing the North Atlantic Sicyonis biotrans Riemann-Zürneck, 1991 , which possesses small filaments on mesenteries of the youngest cycle, Riemann-Zürneck (1991) argued that this character is not stable in Sicyonis . However, she did not provide evidence for that assertion, and the character appears consistent, to judge by specimens of Sicyonis we examined and descriptions of other species in the genus we read. Because the presence or absence of filaments on mesenteries of the youngest cycle is the only feature distinguishing the genera, and we are aware of no evidence that this character is unstable, the species is properly Parasicyonis biotrans (Riemann- Zürneck, 1991).

Material examined. See Appendix 8.

Differential diagnosis. Sicyonis careyi n. sp. can be distinguished from its congeners by its combination of: smooth mesoglea; smooth and thin pedal disc; weak alveolar marginal sphincter muscle; oral stomata; about 80 aborally thickened tentacles; about 80 pairs of mesenteries, of which those of the youngest and rarely the penultimate cycle are fertile.