Edwardsianthus gilbertensis Carlgren, 1931

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 gilbertensis Carlgren, 1931

Japanese name: minami-mushimodoki-ginchaku: Uchida & Soyama, 2001 Figs 3F-J , 4

Edwardsia gilbertensis Carlgren, 1931: 10-12, figs 7-9.

Edwardsianthus gilbertensis : England, 1987: 218, 231, fig. 10; Uchida and Soyama, 2001: 49.

Material examined.

CMNH-ZG 06527: dissected specimen, histological sections, tissues in paraffin, and prepared nematocysts, collected by wading on 7 June 2013 from the intertidal zone of Kabira Bay, Ishigaki Island, Okinawa Pref., Japan, by Kensuke Yanagi ; NSMT-Co 1701: dissected specimens (2 individuals), collected by hand during wading on 26 March 2015 from the intertidal zone of Funaura Bay , Iriomote Island , Okinawa Pref., Japan, by Takato Izumi ; NSMT-Co 1781: dissected or whole specimens (3 individuals), collected by wading on 17 March 2015 from the intertidal zone of Yonaha Bay , Miyako Island , Okinawa Pref., Japan, by Takato Izumi ; NSMT-Co 1782: histological sections, tissues in paraffin, and prepared nematocysts, collected by wading on 19 March 2014 from the intertidal zone of Kataburu Beach , Yonaguni Island , Okinawa Pref., Japan, by Takato Izumi ; NSMT-Co 1783: histological sections, tissues in paraffin, and prepared nematocysts, collected by wading on 23 March 2015 from the intertidal zone of Kataburu Beach , Yonaguni Island , Okinawa Pref., Japan, by Takato Izumi ; NSMT-Co 1784-NSMT-Co 1789: whole or dissected specimens, collected by wading on 17 March 2016 from the intertidal zone of Kataburu Beach , Yonaguni Island , Okinawa Pref., Japan, by Takato Izumi ; NSMT-Co 1790: dissected specimens (3 individuals), collected by wading on 24 March 2015 from the intertidal zone of Higawa Bay , Yonaguni Island , Okinawa Pref., Japan, by Takato Izumi ; NSMT-Co 1791: histological sections, tissues in paraffin, collected by wading on 23 September 2014 from the intertidal zone of Senaga Island , Okinawa Pref., Japan, by Takato Izumi ; NSMT-Co 1792: histological sections, tissues in paraffin, collected by wading on 21 September 2014 from the intertidal zone of Yagaji Island , Okinawa Pref., Japan, by Takato Izumi ; NSMT-Co 1793: histological sections, tissues in paraffin, collected by hand during snorkeling on 9 November 2015 from Shio-michi , Kikai Island , Kagoshima Pref., Japan, 1 m depth, by Takato Izumi .

Description.

External anatomy. Size: preserved specimens ca. 20-60 mm in whole length, and 2.5-3.5 mm in width, with worm-like form, and equal width along whole body. Column: consisting of capitulum, scapus, and physa. The distal-most part capitulum, translucent or opaque gray in color in living specimens, short, without nemathybomes. Scapus with thick periderm-like cuticle, brownish orange in color, both in living and preserved specimens, and with tiny, pale white in color, more or less in 8 rows nemathybomes. Aboral end apparent physa (Fig. 4A ). Tentacles: 20 in number in two cycles; inner tentacles four or five and outer 10-15, opaque whitish gray in color in living animals (Fig. 4B ; this color is lost in preserved specimen), without acrospheres. Inner tentacles slender, ca. 1 mm in length, and outer ones long, slender, short, with sparse white spots on surface, 2-3 mm in length. Mouth: at the center of oral disc, a little swollen. Internal anatomy. Mesenterial arrangement: eight perfect mesenteries, all macrocnemes. Four dorsal and ventral directives, and four lateral mesenteries not paired with other macrocnemes, (Fig. 4E ). All macrocnemes are present along the whole body length from oral to aboral end, and bear distinct retractor and parietal muscles. Approximately seven to 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, distinct and diffused (Fig. 4E, F ), pennon-like, consist of ca. 15-35 simple or slightly branched muscular processes (Fig. 4F ). Parietal muscles: distinctly developed, leaf-like shape elongated along mesenteries, with ca. ten simple or slightly branched muscular processes in each side (Fig. 4F ). Others: each with one tentacle from each endo- or exocoel. Actinopharynx short, limited in uppermost part (Fig. 4C ), without siphonoglyph. Tentacular circular muscle indistinct, and longitudinal muscle distinct, ectodermal. Mesoglea thickest in body wall (Fig. 4E ), and comparatively thick in tentacles (Fig. 4C ), but thinner in mesenteries and parietal muscles (Fig. 4F ). Nemathybomes protruding from mesoglea (Fig. 4D ). Marginal sphincter muscle and basilar muscle absent. Gametogenic tissue not attached to retractor muscles, distinct, but no mature gametocyte. Zooxanthellae sparsely distributed on endoderm of mesenteries (Fig. 4F ). Cnidom. Basitrichs, spirocysts, and microbasic p -mastigophores. See Fig. 3F-J and Table 4 for sizes and distributions of cnidae.

Remarks.

Edwardsia gilbertensis was originally described from the Gilbert Islands, Kiribati (Carlgren, 1931), and there have been several reports from other localities in the tropical/subtropical zone in the Pacific (Fautin, 2013). However, there were no records of E. gilbertensis from Japan except for a fieldguide (Uchida & Soyama, 2001), which reported this species from Kabira Bay, Ishigaki Island. In this research we discovered many individuals of E. gilbertensis living not only in the intertidal zone of Kabira Bay in Ishigaki Island (Fig. 4B ), but also across a broad area of the Nansei Islands, from Kikai Island, Amami Islands (Kagoshima Pref.) to Yonaguni Island, Yaeyama Islands (Okinawa Pref.). The morphological features of these specimens almost completely correspond to the original description of Carlgren (1931): 6.5 cm in length and 0.2 cm in width in fixed specimens; 16-20 tentacles; nemathybomes more or less in rows; 20-30 muscular processes on retractors. The cnidom of our specimen also agrees well with the original description, especially concerning the point that there is only one type of cnidae, "31-41 × (2)2.5(3) µ” in size (Carlgren, 1931) in the nemathybomes. Thus, it is confirmed that Edwardsianthus gilbertensis is widely distributed in the southern islands of Japan including Ishigaki Island.

Figures

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 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.