Edwardsianthus smaragdus, Izumi & Fujii, 2021

Izumi, Takato & Fujii, Takuma, 2021, Gems of the southern Japanese seas - four new species of Edwardsianthus (Anthozoa, Actiniaria, Edwardsiidae) with redescriptions of two species, ZooKeys 1076, pp. 151-182 : 151

Edwardsianthus smaragdus sp. nov.

Japanese name: emerarudo-mushimodoki-emeginchaku Figs 7E-H , 8

Material examined.

Holotype. CMNH-ZG 09762: histological sections, tissues in paraffin, and prepared nematocysts, collected by SCUBA diving on 31 January 2016, off Shirahama seashore, Amami-Oshima Island, Kagoshima, Japan, 15 m depth, by Daisuke Uyeno.

Description.

External anatomy. Size: preserved specimen ca. 70 mm in whole length, and ca. 15 mm in width, and ca. 100 mm in living specimen. Column: cylinder-like in form, and the middle part swollen to some extent (Fig. 8A, B ). The column consisting of capitulum, scapus and quite small physa. The distal-most part of the capitulum whitish transparent in living animals, short, without nemathybomes. Scapus with thick periderm, brownish black in color, and with protruding scattered tiny, dingy grey color nemathybomes in the living specimen (Fig. 8A ). Aboral end differentiated small, tapered physa. Tentacles: 20 in number in two cycles: inner tentacles five and outer 15, brilliant green in color and pale purple at the tips, no pattern, comparatively slender, without acrospheres. Inner tentacles ca. 7 mm and outer ones ca. 10-15 mm in length in the living specimen. Mouth: at the center of oral disc, slightly swollen both in living and preserved specimen. Internal anatomy. Mesenterial arrangement: eight perfect mesenteries, all macrocnemes. Four dorsal and ventral directives, and four lateral mesenteries not paired with other macrocnemes, arranged in normal Edwardsia pattern (Fig. 8F ). All macrocnemes are present along the whole body length from oral to aboral end and bear distinct retractor and parietal muscles. Twelve tiny microcnemes, without muscles, only confined to distal-most part. Four microcnemes between dorsal directives and dorso-lateral mesenteries, four between dorso-and ventro-lateral mesenteries, and four between ventro-lateral mesenteries and ventral directives. Each tentacle exo- or endocoelic. Retractor muscles: at the mid part of column, weakly developed but distinct, diffused (Fig. 8C ), pennon-like, arranged with 50-60 muscular processes, simple or slightly branched. One process nearest to body wall well-branched (Fig. 8C ). Parietal muscles indistinct, elongated in direction of mesenteries, consisted of short and slightly branched processes, sparsely, <ten on each side (Fig. 8C ). Others: each with one tentacle from each endo- or exocoels. Existence of siphonoglyph unknown because of contracted state of specimen. Tentacular circular muscle endodermal, distinct, and longitudinal muscle ectodermal, both distinct. Mesoglea thickest in body wall and actinopharynx, maximum 400 µm in thickness (Fig. 8F ), but far thinner in parietal muscle and tentacles (Fig. 8C-E ), and thinnest, <10 µm, in mesenteries. Nemathybomes protruding from mesoglea (Fig. 8H ). Marginal sphincter muscle and basilar muscle absent. Gametogenic tissue apart from retractor muscles, distinct (Fig. 8G ), with matured oocytes. Cnidom. Basitrichs, spirocysts, microbasic p -mastigophores. See Fig. 7E-H and Table 5 for sizes and distribution.

Etymology.

This species epithet refers to an emerald, a gemstone, and is named so after the bright green coloration of its tentacles. Derivation of the Japanese name is the same as that of the Latin species name.

Remarks.

Edwardsianthus species usually have strongly developed and diffused retractor and parietal muscles (Figs 2F , 4F , 5E , 6E , 9E ), but those of Edwardsianthus smaragdus form an exception by their less distinct development (Fig. 8F ). This character is clear in addition to its brilliant light green tentacles. Concerning the cnidom, E. smaragdus can be distinguished from E. pudicus and E. gilbertensis by containing two types of basitrichs in its nemathybomes, and from the other three new species of Edwardsianthus by having microbasic p -mastigophores in its actinopharynx (Tables 4 , 5 ).

In the phylogenetic tree (Fig. 10 ; Suppl. material 1 Fig. S1), E. smaragdus sp. nov. has a far longer branch than the other species, and therefore its phylogenetic position is not stable; the ML bootstrap value was 57, which is comparatively low, and not supported by BI posterior probability; Fig. 10 ). Nevertheless, it is most probable that E. smaragdus n. sp. belongs to this genus (ML bootstrap value was 79) despite the BI posterior probability not being well-supported. Considering that the morphology of this species corresponds completely with the diagnosis of Edwardsianthus , this species is classified as E. smaragdus .

Figures

Figure 2. External and internal morphology of Edwardsianthus pudicus (NSMT-Co 1702) A outer view of living specimen B oral view of living specimen C longitudinal section of tentacle D transverse section of tentacle E transverse section of parietal muscle F transverse section of macrocnemes G longitudinal section of physa. Abbreviations: cap, capitulum; fi, filament; me, mesoglea; pa, parietal muscle; ph, physa; rm, retractor muscle; scs, scapus; te, tentacle; tlm, tentacular longitudinal muscle. Scale bars: 5 mm (A, B); 1 mm (C); 500 µm (D, F, G); 100 µm (E).

Figure 4. External and internal morphology of Edwardsianthus gilbertensis (CMNH-ZG 06527 except for B) A outer view of preserved specimen B oral view of living specimen with 18 tentacles in the habitat C longitudinal section of oral end D transverse section of nemathybome E transverse section of column in lower part; F. Enlarged view of transverse section of mesenteries. Abbreviations: a, actinopharynx; cap, capitulum; fi, filament; ma, macrocneme; ne, nemathybomes; pa, parietal muscle; ph, physa; rm, retractor muscle; scs, scapus; te, tentacle. Scale bars: 5 mm (A); 1 mm (B); 500 µm (C, E, F); 100 µm (D). Photograph B by Kensuke Yanagi.

Figure 5. External and internal morphology of Edwardsianthus carbunculus sp. nov. (CMNH-ZG 05954) A outer view of preserved specimen (aboral end is damaged) B oral view of living specimen in the habitat (photograph Kensuke Yanagi) C transverse section of column in upper part D transverse section of lower column in lower part E transverse section of the macrocneme F transverse section of testis G transverse section of nemathybomes. Abbreviations: a, actinopharynx; cap, capitulum; fi, filament; me, mesoglea; ne, nemathybomes; pa, parietal muscle; rm, retractor muscle; scs, scapus; te, tentacle. Scale bars: 5 mm (A, B); 500 µm (C-F); 100 µm (G). Picture B taken by Kensuke Yanagi.

Figure 6. External and internal morphology of Edwardsianthus sapphirus sp. nov. (CMNH-ZG 09761). A oral view of living specimen in the habitat B outer view of preserved specimen; C. Transverse section of column in upper part D enlarged view of transverse section of parietal muscle E enlarged view of transverse section of retractor muscle F transverse section of ovary G longitudinal section of tentacle H transverse section of tentacle. Abbreviations: a, actinopharynx; fi, filament; me, mesoglea; ne, nemathybome; oo, oocytes; pa, parietal muscle; ph, physa; rm, retractor muscle; scs, scapus; te, tentacle; tlm, tentacular longitudinal muscle. Scale bars: 1 cm (A, B); 500 µm (C-E); 100 µm (F-H).

Figure 7. Cnidae of Edwardsianthus species A-D E. sapphirus sp. nov. (CMNH-ZG 09761) A 1 spirocyst in tentacle A 2 basitrich in tentacle B 1 small basitrich in actinopharynx B 2 large basitrich in actinopharynx C 1 small basitrich in nemathybome C 2 large basitrich in nemathybome D 1 small basitrich in filament D 2 large basitrich in filament D 3 microbasic p - mastigophore in filament E-H E. smaragdus sp. nov. (CMNH-ZG 09762) E 1 spirocyst in tentacle E 2 basitrich in tentacle F 1 small basitrich in actinopharynx F 2 large basitrich in actinopharynx F 3 microbasic p - mastigophore in actinopharynx G 1 small basitrich in nemathybome; G 2 large basitrich in nemathybome; H 1 spirocyst in filament; H 2 small basitrich in filament H 3 large basitrich in filament H 4 microbasic p - mastigophore in filament I-K E. amethystus sp. nov. (CMNH-ZG 09763) I 1 spirocyst in tentacle I 2 basitrich in tentacle J 1 small basitrich in actinopharynx J 2 large basitrich in actinopharynx K 1 spirocyst in filament K 2 small basitrich in filament K 3 large basitrich in filament K 4 microbasic p - mastigophore in filament.

Figure 8. External and internal morphology of Edwardsianthus smaragdus sp. nov. (CMNH-ZG 09762). A outer view of living specimen B outer view of preserved specimen C transverse section of retractor muscle D transverse section of the tentacle E longitudinal section of the tentacle F transverse section of column G enlarged view of transverse section of ovary H transverse section of a nemathybome. Abbreviations: a, actinopharynx; cap, capitulum; fi, filament; ma, macrocneme; me, mesoglea; ne, nemathybomes; ov, ovary; pa, parietal muscle; ph, physa; rm, retractor muscle; scs, scapus; te, tentacle; tcm, tentacular circular muscle; tlm, tentacular longitudinal muscle. Scale bars: 1 cm (A, B); 500 µm in (C - H).

Figure 9. External and internal morphology of Edwardsianthus amethystus sp. nov. (CMNH-ZG 09763) A oral view of living specimen in the habitat B outer view of preserved specimen C longitudinal section of tentacle D transverse section of tentacle E transverse section of retractor muscle F transverse section of testis G transverse section of trace of nemathybome. Abbreviations: fi, filament; me, mesoglea; ne, nemathybome-like structure; pa, parietal muscle; rm, retractor muscle; scs, scapus; te, tentacle; tlm, tentacle longitudinal muscle; ts, testis. Scale bars: 1 cm (A, B); 500 µm (E, F); 100 µm (C, D, G).

Figure 10. Maximum-likelihood tree of the order Actiniaria based on the combined dataset of mitochondrial 12 S and 16 S and nuclear 18 S rDNA (total 2866 bp). The clade of the genus Edwardsianthus is colored in a red box. Red bar at node indicates the position at which nemathybomes would be obtained. Numbers indicate ML bootstrap support values followed by BI posterior probabilities of the nodes (bootstrap values of ≥ 50 % and posterior probabilities ≥ 0.5 are shown).