Actinoscyphia groendyki, 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 : 15-18

Actinoscyphia groendyki n. sp.

( Figures 9–12, Table 2, Appendix 5)

Body form and size. Exposed mesoglea of specimens light grey to tan; some with dingy grey ectoderm sloughing off. Mesoglea thick throughout column, to 8 mm at proximal end of specimen 33 mm long. Column smooth and stiff; tapers from distal end. Margin contracted so column covers most tentacles. Oral disc in nearly all specimens examined folded in half perpendicular to long axis, giving animals Venus flytrap posture ( Figure 9). Pedal disc elongate; long axis in same direction as long axis of oral disc.

Column 9–42 mm long; long axis of pedal disc approximately same length as long axis of oral disc, typically longer than column.

Pedal disc. Pedal disc tan or light brown; most specimens with metallic brown chitinous material, inferred to be secreted by animal, closely associated with pedal disc. Most elongate, from 4 to 134 mm; in large specimens pedal disc wrapped around or appears to have been wrapped around cylindrical object such as worm tube or group of sponge spicules ( Figure 9). In small specimens (about 10 mm column length) pedal disc small, concave, holds bolus of mud.

Oral disc and tentacles. Oral disc tan or salmon, oval, radially furrowed along mesenterial insertion; folds in half, hiding tentacles.

Mouth circular, approximately 1/4 oral disc diameter; with raised lips. Slightly darker than oral disc, or deep purple; tan or light brown radial stripe typically at oral end of each siphonoglyph.

Tentacles slightly lighter in color than oral disc, smooth; tapered (1–4 mm at widest part of base to 0.1–1 mm at tip), 1–12 mm long, all thickened aborally with mesoglea. Most specimens with 120–149 tentacles (one small

Internal anatomy. Actinopharynx deep purple, very long, longitudinally sulcate. Each of two symmetrical siphonoglyphs attached to pair of directive mesenteries; directive plane perpendicular to long axis of oral and pedal discs.

Mesenteries thin, typically arrayed in five cycles (specimens about 10 mm column length possess only four cycles); develop distally. All mesenteries with filaments; those of only first cycle complete, stomata absent. Mesenteries of first cycle sterile; mesenteries of second cycle rarely fertile; all younger mesenteries may be fertile. Mesenteries of youngest cycle regularly arrayed; all pairs do not develop simultaneously: one pair flanking a pair of preceding cycle develops on side nearer older pair of mesenteries (i.e. 115544 55 33 55 445522, bolded 5s represent where late-developing pairs will presumably appear, although absent in specimens examined) ( Figure 10a). Pattern holds for fourth cycle mesenteries; in one specimen both pairs flanked those of third cycle in some places, and only one pair had developed in others. Retractor muscles very weak and short; parietobasilar muscles weak.

Mesogleal marginal sphincter muscle weak, moderately long (to approximately 1/3 column length), with many alveoli, slightly striated transversely in some specimens ( Figure 10b), or distinctively striated only near proximal end. Situated in middle of mesoglea distally where broadest, occupies approximately half mesoglea width; tapers and approaches endoderm proximally. Alveoli pigmented, giving sphincter muscle tan color. Distal alveoli small and may be spaced apart or clumped; proximal alveoli larger.

Longitudinal muscles of tentacles mostly ectodermal with little mesogleal involvement, circular muscles endodermal ( Figure 10c).

Cnidae. Gracile and robust spirocysts, basitrichs, holotrichs, microbasic p -mastigophores. Sizes and distribution of cnidae given in Table 2; cnidae illustrated in Figure 11.

Type specimens. Holotype: SBMNH 149661 , collected 19-Feb-1971 from 44.99° N 126.66° W, 2,770 m. Column length 34 mm, oral disc folded 30 x 45 mm, and elongate pedal disc 40 mm. Fourth cycle of mesenteries developed, fifth cycle partially developed; 149 tentacles.

Paratypes: SBMNH 149662 , 1 specimen, collected 19-Feb-1971 from 44.99° N 126.66° W, 2,770 m ; KUIZ 003350 , 1 specimen, collected 19-Feb-1971 from 44.99° N 126.66° W, 2,770 m ; KUIZ 003351 , 1 specimen, collected 18-Feb-1971 from 45.29° N 126.47° W, 2,710 m ; USNM 1149362 , 1 specimen, collected 18-Feb-1971 from 45.29° N 126.47° W, 2,710 m ; CAS 184531 , 1 specimen, collected 18-Feb-1971 from 45.29° N 126.47° W, 2,710 m ; RBCM 010-00571 - 001 , 1 specimen, collected 18-Feb-1971 from 45.29° N 126.47° W, 2,710 m .

Etymology. Named in honor of Eash-Loucks’ late grandfather, James Groendyk.

Distribution. Actinoscyphia groendyki n. sp. occurs in both the Southern and northeastern Pacific oceans and has been collected from depths of at least 636 to 3,819 m ( Figure 12).

Taxonomic remarks. We re-examined some of the 18 specimens from the Southern Ocean that Fautin (1984) had identified as Actinoscyphia plebeia ( McMurrich, 1893) . Features of specimens from the northeastern Pacific conform to what she reported except that 1) the microbasic p -mastigophores of the actinopharynx and the large basitrichs of the mesenterial filaments are smaller, and 2) mesenteries of the first cycle are always sterile whereas Fautin reported that only the directives and some mesenteries of the youngest cycle are sterile.

In the actinopharynx of specimens Fautin (1984) examined, we found small microbasic p -mastigophores (the smallest was 26.1 x 4.0 µm), which fall within the same size range as those of specimens of A. groendyki n. sp. Therefore, the only difference we found between specimens from the northeastern Pacific and Southern oceans was the size of large basitrichs in the mesenterial filaments, whose lengths overlaps by 1 µm. However, these nematocysts were not found in all specimens from the Southern Ocean, so they may be contaminants from the actinopharynx. We conclude that the specimens from the northeastern Pacific, as well as those examined by Fautin (1984), constitute a single species. In specimens from both localities, all mesenteries of the first cycle were sterile,

as were those of the second cycle in most specimens. Thus these specimens clearly fall within the original diagnosis of Actinoscyphia by Stephenson (1920), which includes the first cycle of mesenteries being complete and sterile.

Some features of the specimens we examined from the northeastern Pacific and those identified by Fautin (1984) as A. plebeia differ from those of Actinoscyphia plebeia as originally described by McMurrich (1893); therefore, we also examined the holotype of A. plebeia (USNM 17789).

USNM 17789 has 235 tentacles (a small portion of the margin, about 1/15, including tentacles was removed). However, McMurrich (1893) described the species as having only 96 tentacles. The number of tentacles we observed corresponds to the number of mesenteries in the specimen, because the fifth cycle was fully developed and some members of the sixth cycle of mesenteries were observed.

The number of tentacles and mesenteries of the holotype of A. plebeia distinguish that species from the northeastern Pacific specimens of Actinoscyphia and those reported by Fautin (1984). Additionally, the new species is distinguished from A. plebeia by the length and shape of the sphincter muscle (short and distinctly transversely striated throughout its entire length in A. plebeia ), thickness of the mesoglea (much thinner in A. plebeia ), oral stomata in A. plebeia , and cnidae (most notably the lack of holotrichs in the tentacles of A. plebeia , although this may be due to the condition of the specimen) (Table 2) (see Dichotomous key of Actinoscyphia ).

Because Actinoscyphia groendyki n. sp. occurs in both the Southern and northeastern Pacific Oceans, we consider it likely that Actinoscyphia groendyki n. sp. occurs in the Southeastern Pacific Ocean as well. This also means that the analysis of Rodríguez et al. (2007) for A. plebeia must be reconsidered.

Material examined. See Appendix 5.

Differential diagnosis. Actinoscyphia groendyki n. sp. can be distinguished from its congeners by its combination of: elongate pedal disc; oval oral disc; to about 150 tentacles that are thickened aborally; five cycles of mesenteries (to 144 mesenteries at limbus), of which six pairs are complete and the first and typically the second cycle are sterile; absence of stomata; moderately long mesogleal marginal sphincter muscle with pigmented alveoli.