Edwardsianthus sapphirus, 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 sapphirus sp. nov.

Japanese name: safaia-mushimodoki-ginchaku Figs 6 , 7A-D

Material examined.

Holotype. CMNH-ZG 09761: histological sections, tissues in paraffin, and prepared nematocysts, collected by SCUBA diving on 24 June 2012, in Oura Bay , Okinawa Island, Okinawa Pref., Japan, 10 m depth, by Takuma Fujii.

Description.

External anatomy. Size: preserved specimen ca. 150 mm in whole length, and 20 mm (narrower part)-35 mm (broader part) in width, and> 300 mm in living animal. Column: cylinder-like form, and the proximal part swollen to some extent in preserved specimen. The column consisting of capitulum, scapus and quite small physa. The distal-most part of the capitulum transparently blue, short, without nemathybomes. Scapus with thin and easily stripped periderm, brown in color, and with quite numerous, tiny, pale white in color, scattered nemathybomes (Fig. 6B ). Nemathybomes. Aboral end differentiated small, tapered physa. Tentacles: 20 in number in two cycles: inner tentacles 5 and outer 15, metallic greenish blue in color with no pattern in living specimen (Fig. 6A ; this color lost in preserved specimen), slender, without acrospheres. Inner tentacles ca. 10 mm and outer ones 15-25 mm in length in the living specimen. Mouth: at the center of oral disc, apparently swollen in living animal (Fig. 6A ). 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. 6C ). 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. 6E ), pennon-like, arranged with 120-150 muscular processes, simple or slightly branched. One process nearest to body wall extremely well-branched, with> 100 secondary and thirdly branched processes (Fig. 6E ). Parietal muscles: distinct, developed peculiarly: consisted of ca. 20-30 processes in each side, and only one of them extremely developed, branched into secondary 15-25 processes, and expanded broadly. Thus, parietals in entirety appearing in a characteristic shape like the club symbol of cards (Fig. 6D ). Others: each with one tentacle from each endo- or exocoels. Existence of siphonoglyph unknown because of contracted state of specimen. Tentacular circular muscle endodermal, indistinct (Fig. 6G ), and longitudinal muscle ectodermal, distinct, and sometimes pinnated (Fig. 6H ). Mesoglea thickest in body wall, sometimes reaching 1 mm in thickness (Fig. 6C ), but thinner in mesenteries, parietal muscle, and tentacles (Fig. 6E-H ). Nemathybomes protruding from mesoglea. Marginal sphincter muscle and basilar muscle absent. Gametogenic tissue apart from retractor muscles, distinct (Fig. 6C, F ), with matured oocytes. Cnidom. Basitrichs, spirocysts, microbasic p -mastigophores. See Fig. 7A-D and Table 5 for sizes and distribution.

Etymology.

The species epithet refers to a sapphire, a gemstone, and is named so after the brilliant metallic blue color of the species’ tentacles. Derivation of the Japanese name is the same as that of the Latin species name.

Remarks.

This species is one of the largest species of its family. It is not only characterized by its gigantic body size, and bluish metallic tentacle coloration, but also by the strange club-like shape of its parietal muscles. Congeneric species have parietal muscles with simple or slightly branched processes, and there are no confirmed cases of parietal muscles with such secondary branched muscular processes in other species. Thus, the shape of parietal muscle of this species is very conspicuous within its genus, allowing E. sapphirus to be distinguished easily from its congeners.

There have been several observations of the metallic blue tentacles resembling this species reported during SCUBA diving in Amami Oshima by Takuma Fujii and some other divers (Atetsu Bay and some other places). However, it was too difficult to dig out such large edwardsiid sea anemones that are buried deeply in the substrate, as they usually retract their whole bodies quickly into the substrate. Therefore, we think that the difficulty in collecting multiple specimens is the most serious issue that needs to be overcome in order to make additional progress in the study of edwardsiids.

Figures

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.