Edwardsianthus England, 1987

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

Genus Edwardsianthus England, 1987

Diagnosis

(revised from the diagnosis given by England, 1987). Body divisible into physa, scapus, and capitulum. physa short, without nemathybomes or cuticle. Scapus long, generally with nemathybomes but sometimes without, sunk in mesoglea; cuticle present. Tentacles usually 20, inequal number at inner and outer cycle: five-eight inner and 12-15 outer. Siphonoglyph weak or absent, ventral. Mesenteries eight macrocnemes and six pairs of microcnemes, minute and restricted to distal part of column. Microcnemes never paired with macrocnemes. Gametogenic tissue, filaments, and parietal and retractor muscles on macrocnemes only. Parietals well developed; retractors strong-diffuse to restricted-reniform. Cnidom: spirocysts, basitrichs, microbasic p -mastigophores.

Type species.

Edwardsia pudica Klunzinger, 1877 (currently recognized as Edwardsianthus pudicus (Klunzinger, 1877); the genus name is masculine). Type locality is Egypt, Red Sea.

Derivation of Japanese name.

This name is constructed from nanyo (south sea), mushimodoki-ginchaku (worm-like sea anemone).

Remarks.

Since England (1987) established this genus, no new species were described in addition to the two that were already known. This study revises the diagnosis of the genus for the first time in the 30 years since its original description, including new evidence for four new species.

In the present study, sea anemones resembling Edwardsianthus were collected from several Japanese localities (Fig. 1 ). According to our analyses, these edwardsiids were shown to belong to the same phylogenetic clade as E. pudicus and E. gilbertensis (Fig. 10 ) and also shared the same mesenterial arrangement, i.e., lacking four microcnemes on the first mesenterial cycle. Therefore, these new species fit well with the definition of Edwardsianthus given by England (1987). Thus, we have placed these four new species within Edwardsianthus as Edwardsianthus carbunculus sp. nov., E. sapphirus sp. nov., E. smaragdus sp. nov., and E. amethystus sp. nov..

England (1987) also stated that the genus Edwardsianthus has only one type of basitrich in the nemathybomes. However, Edwardsianthus carbunculus sp. nov., Edwardsianthus sapphirus sp. nov., and Edwardsianthus smaragdus sp. nov. have two types of basitrichs in their nemathybomes, and Edwardsianthus amethystus has no nemathybomes at all. Consequently, we have now added a new character to the diagnosis of this genus: an inequal number of inner and outer tentacles. Species of this genus have a peculiar tentacular arrangement as "5 inner and 15 outer" or "8 inner and 12 outer". The tentacular arrangement is useful to distinguish Edwardsianthus from the genus Edwardsia de Quatrefages, 1842 of the same family, as Edwardsia species have equal numbers of tentacles in their inner and outer cycles (Carlgren, 1949; Izumi & Fujita, 2019).

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 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).