Edwardsianthus carbunculus, 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 carbunculus sp. nov.

Japanese name: rubi-mushimodoki-ginchaku Figs 3K-O , 5

Material examined.

Holotype. CMNH-ZG 05954, histological sections, tissues in paraffin, and prepared nematocysts, collected by SCUBA diving on 10 July 2013, Nishidomari (in front of Kuroshio Biological Institute), Kochi Pref., Japan, 5 m depth, by Kensuke Yanagi.

Description.

External anatomy. Size: preserved specimen ca. 60 mm in whole length, and 10-15 mm in width (but distal side strongly contracted and aboral side torn off during sampling, so body length estimated> 100 mm when living), with cylinder-like form, and the proximal side a little narrower. Column: consisting of capitulum and scapus. The distal-most part of capitulum, transparent and visible scarlet color inside, short, without nemathybomes. Scapus with very thick periderm-like cuticle, dark brown in color in living specimen (Fig. 5B ; this color lost in preserved specimen), and with tiny, pale white in color, densely scattered nemathybomes (Fig. 5A ). Tentacles: 20 in number in two cycles: inner tentacles five and outer 15, vivid scarlet in color (Fig. 5B ), without acrospheres. Inner tentacles short, blunt, ca. 6 mm in length, and outer ones long, slender, with sparse white spots on surface, 15-20 mm in length in the living specimen. Mouth: at the center of oral disc apparently swollen in living animal (Fig. 5B ). 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. 5C, D ). 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. Retractor muscles: at the mid part of column, strongly developed and diffused (Fig. 5E ), pennon-like, arranged with 60-90 muscular processes, simple or slightly branched, and pinnated in some parts. Some processes nearest to body wall extremely well-branched, into secondary and thirdly branches (Fig. 5E ). Parietal muscles: not so well developed, apparently elongated to direction of mesenteries, with ca. 20-30 simple to muscular processes in each side (Fig. 5E ). Others: each with one tentacle from each endo- or exocoels. Existence of siphonoglyph unknown because of contracted state of specimen. Tentacular circular muscle indistinct, and longitudinal muscle distinct, ectodermal. Mesoglea thickest in body wall,> 200 μm in thickness in some parts (Fig. 5C, D ), and comparatively thick in tentacles and mesenteries (nearby retractor), but thinner in parietal muscles (Fig. 5E ). Nemathybomes protruding from mesoglea (Fig. 5G ). Marginal sphincter muscle and basilar muscle absent. Gametogenic tissue apart from retractor muscles, distinct, with dense immature testes (Fig. 5F ). Cnidom. Basitrichs, spirocysts, and microbasic p -mastigophores. See Fig. 3K-O and Table 4 for sizes and distributions of cnidae.

Etymology.

The species epithet refers to ruby, a kind of gemstone, and is named so after the scarlet, vivid red, color of its tentacles. Derivation of the Japanese name is the same as that of the Latin species name.

Remarks.

This species can be distinguished from Edwardsianthus not only by the scarlet tentacles, the most characteristic feature of this species, and their arrangement, but also by the species’ cnidom: E. carbunculus can be distinguished from E. gilbertensis and E. pudicus by having two types of basitrichs in its nemathybomes (Table 4 ), and from the other three new species by containing only one type of basitrich in its filaments (Tables 4 , 5 ). In the phylogenetic tree (Fig. 10 ), E. carbunculus sp. nov. is closely related to E. pudicus , but there are differences in their morphology as described above and in the separation of their localities: E. pudicus inhabits tropical and subtropical waters while E. carbunculus were only lives in temperate seas. Therefore, we concluded that this sea anemone is a new species. The genus Edwardsianthus is also traditionally characterized by nemathybomes containing only one type of nematocysts, but this definition needs revision because this species has two types of nematocysts in nemathybomes (Fig. 3M , Table 4 ; compare with the remarks given for the genus Edwardsianthus ).

To complete the description of this species, it is necessary to collect and examine specimens with complete proximal ends. However, this species was collected only once from the type locality, and no additional field observations are known, even despite the presence of its characteristic red tentacles. This species is the only Edwardsianthus species inhabiting the temperate zone: the other Edwardsianthus species live in tropical or subtropical zones (Fig. 1 ; Fautin, 2013). Thus, the locality, Kochi, becomes the northernmost distribution limit of this genus.

Figures

Figure 1. Localities of the specimens of the Edwardsianthus species collected in this study. Purple star marked by p indicates collection locality of Edwardsianthus pudicus; orange stars are those of E. gilbertensis; red star marked by c is E. carbunculus sp. nov.; blue star marked by a is E. sapphirus sp. nov.; green star marked by s is E. smaragdus sp. nov.

Figure 3. Cnidae of Edwardsianthus species A-E E. pudicus (NSMT-Co 1702) A 1 spirocyst in tentacle; A 2 basitrich in tentacle B 1 small basitrich in actinopharynx B 2 large basitrich in actinopharynx B 3 microbasic p - mastigophore in actinopharynx C basitrich in nemathybome D basitrich in column E 1 small basitrich in filament E 2 large basitrich in filament E 3 microbasic p - mastigophore in filament F-J E. gilbertensis (CMNH-ZG 06527) F 1 spirocyst in tentacle F 2 basitrich in tentacle G 1 small basitrich in actinopharynx G 2 large basitrich in actinopharynx G 3 microbasic p - mastigophore in actinopharynx H basitrich in nemathybome I basitrich in nemathybome J 1 basitrich in filament J 2 microbasic p - mastigophore in filament K-O E. carbunculus sp. nov. (CMNH-ZG 05954) K 1 spirocyst in tentacle K 2 basitrich in tentacle L 1 small basitrich in actinopharynx L 2 large basitrich in actinopharynx M 1 small basitrich in nemathybome M 2 large basitrich in nemathybome N basitrich in column O 1 small basitrich in filament O 2 large basitrich in filament O 3 microbasic p - mastigophore in filament.

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 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).