The first species of Actiniaria, Spongiactis japonica gen.n., sp.n. (Cnidaria: Anthozoa), an obligate symbiont of a glass sponge

Abstract

Spongiactis japonica, a new genus and species of Actiniaria, an obligate symbiont of hexactinellid sponge is described from Sagami Bay, Japan, Pacific Ocean. Numerous small specimens of this sea anemone live in the caves in a superficial layer of the sponge Hyalonema sieboldi and probably reproduce asexually. The species has no acontia and it is taxonomically related to Actinoscyphiidae (which members are believed have lost acontia) and to Hormathiidae (comprising species possessing acontia) but cannot be accommodated in either family. It is therefore assigned to the new family Spongiactinidae fam.n. The two related families, Actinoscyphiidae and Hormathiidae may well be united. How to cite this article:

Hidden among Sea Anemones: The First Comprehensive Phylogenetic Reconstruction of the Order Actiniaria (Cnidaria, Anthozoa, Hexacorallia) Reveals a Novel Group of Hexacorals

“…All families previously included within Actiniaria (except Edwardisiidae, Actinernidae and Halcuriidae): Acontiophoridae [75]; Actiniidae [76]; Actinodendridae [77]; Actinoscyphiidae [78]; Actinostolidae [79]; Aiptasiidae [80]; Aiptasiomorphidae [12]; Aliciidae * [81]; Andresiidae* [13]; Andvakiidae [82]; Antipodactinidae [83]; Amphianthidae [72]; Bathyphelliidae [79]; Boloceroididae * [50]; Capneidae [84]; Condylanthidae [13]; Diadumenidae [78]; Exocoelactinidae* [85]; Gonactiniidae * [86]; Halcampidae [87]; Haliactinidae [12]; Haliplanellidae [88]; Haloclavidae * [89]; Hormathiidae [79]; Homostichanthidae [90]; Iosactinidae [91]; Isanthidae [75]; Kadosactinidae [92]; Limnactiniidae* [60]; Liponematidae [72]; Metridiidae [86]; Mimetridiidae [93]; Minyadidae [94]; Nemanthidae [95]; Nevadneidae* [96]; Octineonidae [97]; Oractinidae [98]; Ostiactinidae [11]; Phelliidae [99]; Phymanthidae [87]; Preactiniidae * [100]; Ptychodactinidae* [101]; Ramireziidae [93]; Sagartiidae [102]; Sagartiomorphidae [103]; Spongiactinidae [104]; Stichodactylidae [87]; Thalassianthidae [105].…”

First Detailed Record of Symbiosis Between a Sea Anemone and Homoscleromorph Sponge, With a Description ofTempuractis rinkaigen. et sp. nov. (Cnidaria: Anthozoa: Actiniaria: Edwardsiidae)

“…Moreover, the small size of this species, less than 5 mm in whole body length even for adults, is prominent in this family. Ultimately, the habitat of this spe- cies is very unique for not only edwardsiids but also for sea anemones in general; only Spongiactis japonica Sanamyan, Sanamyan and Tabachnick, 2012 is recorded to be symbiotic with sponges (Sanamyan et al, 2012). Tempuractis rinkai is quite different from S. japonica in morphological features and, of course, belongs to a quite different taxon at the family level.…”

“…In contrast to the diversity of sponge-symbiotic zoanthids, only a single species of Actiniaria is known to live in sponges. The first detailed report of a symbiotic relationship between members of Actiniaria and Porifera was about an actiniarian and a hexactinellid sponge (Sanamyan et al, 2012). According to Sanamyan et al (2012), the host sponge Hyalonema sieboldi Gray, 1832 forms "specific minute volcano-like rises" above the sea anemone Spongiactis japonica.…”

Supplemental Material for 'Sea anemones through X-rays : visualization of two species of Diadumene (Cnidaria, Actiniaria) using micro-CT. (American Museum novitates, no. 3907)'

“…Relevant notes on cnidae terminology: Regardless of whether only Diadumene lineata or more species of the genus possess p-mastigophores B1 in acontia and the reliable identification of nematocysts in this category, the choice of nomenclature used to differentiate p-mastigophores may reveal or obscure this feature. The terminology used by Sanamyan et al (2012) to classify p-mastigophores (i.e., Schmidt, 1969, 1972, 1974, modified by den Hartog, 1995 identifies nematocysts without a "Faltstück" (i.e., without a divided shaft) but with bilateral symmetry as p-mastigophores B2a. By incorporating the modification of den Hartog (1995), differences between D. lineata and other species in the genus as well as among diadumenids and other metridioidean families with "true" p-mastigophores B2a with a Faltstück in the acontia gets blurred (e.g., den Hartog and Ates, 2011;Kovtun et al, 2012).…”

“…We follow a nematocyst terminology similar to the one used by Sanamyan et al (2012), which combines the classification of Weill (1934), modified by Carlgren (1940) and thus differentiating "basitrichs" from "b-mastigophores, " with that of Schmidt (1969Schmidt ( , 1972Schmidt ( , 1974, which captures the underlying variation seen in "rhabdoids. " Unlike Sanamyan et al (2012), we do not modify Schmidt's (1969Schmidt's ( , 1972Schmidt's ( , 1974 nomenclature with den Hartog's (1995) notes on p-mastigophores B1 (see Discussion), but agree with the use of "mastigophore" instead of "rhabdoid" to preserve stability. We use a combination of classifications to better capture the underlying variation in cnida morphology given its imperative nature to actiniarian taxonomy, but do not imply any evolutionary relationship among these types.…”