Epizoanthus fatuus, (SCHULTZE, 1860)

Kise, Hiroki, Montenegro, Javier, Santos, Maria E. A., Hoeksema, Bert W., Ekins, Merrick, Ise, Yuji, Higashiji, Takuo, Fernandez-Silva, Iria & Reimer, James D., 2022, Evolution and phylogeny of glass-sponge-associated zoantharians, with a description of two new genera and three new species, Zoological Journal of the Linnean Society 194, pp. 323-347 : 327-330

EPIZOANTHUS FATUUS ( SCHULTZE, 1860)

( FIG. 3A, B )

Synonymy: Palythoa fatua Schultze, 1860: 36 , taf. 2, figs 1–2; Palythoa fatua — Andres, 1884: 311; Sidisia fatua — Lwowsky, 1913: 589–596, taf. 19, figs 5–8; Sidisia fatua var. alba — Lwowsky, 1913: 597.

Material examined: MISE-HK33-2 (NSMT-Co 1757), off Amakusa , Kumamoto, Japan, 32°24 ′ 44.8 ″ N 129°28 ′ 01.3 ″ E (position approximate, exact location unknown), 1000 m depth, beat trawl, coll. D. Uyeno on the training vessel Nagasaki-maru, 2011, fixed in 99.5% ethanol. MISE-HK132 (NSMT-Co 1758), Sagami Bay, Kanagawa, Japan, 35°08 ′ 27.5 ″ N –35°0 8 ′ 33.5 ″ N, 139°32 ′ 12.2 ″ E –139°32 ′ 44.3 ″ E, 133–274 m depth, dredging, coll. H. Kotsuka on vessel Rinkaimaru, 12 Feb 2015, fixed in 99.5% ethanol .

Description: External morphology. Ten to 50 cylindrical polyps connected by strongly developed dark brown and light beige coenenchyme on stalks of hexactinellid sponges ( Hyalonema sp. ) in preserved specimens. Column of preserved polyps dark brown and light beige in coloration. Colonies covered upper part of stalks, but not around the spiculous anchor. Contracted preserved polyps 0.8–2.9 mm in height, 1.9–3.6 mm in diameter. Capitulum swollen, and diameter of capitulum larger than scapus when contracted. Capitulary ridges present and strongly pronounced when contracted, 14 in number. The number of tentacles of each polyp in this study 28, and tentacles arranged in two rows. Ectoderm and mesoglea of polyps and coenenchyme heavily encrusted with numerous sand and silica particles.

Internal morphology: Zooxanthellae absent. Number of mesenteries 28, in macrocnemic arrangement. Mesogleal thickness 0.1–0.3 mm and gradually wider in direction from capitulum towards scapus. Mesoglea either as thick as or thinner than ectoderm. Reticulate mesogleal musculature. Siphonoglyph distinct and V-shaped. Mesenterial filaments present. Habitat and distribution: Indo-Pacific Ocean: near Indonesia ( Carlgren, 1923), East China Sea ( Pei 1998), the Bay of Bengal, India and Japan ( Lwowsky, 1913).

Associated host. Hyalonema spp.

Remarks: This species has been reported in several studies, which indicate the presence of intraspecific variation ( Andres, 1884; Lwowsky, 1913, Carlgren, 1923). In fact, we observed several morphological differences, such as coloration and polyp dimensions, between the two examined specimens (NSMT-Co 1757 and NSMT-Co 1758). Also, some genetic variation of E. fatuus was observed in ITS-rDNA sequences (8 bp), and thus the possibility remains that E. fatuus contains cryptic species, as ITS-rDNA has been demonstrated to be among the most variable genetic regions currently utilized to delineate species within Zoantharia (e.g. Reimer et al., 2007; Montenegro et al., 2015). However, the sequences of the two examined specimens formed a strongly supported monophyletic clade and we therefore identify the examined specimens as a single species in this study. Additional specimens and fine-scale genetic analyses are required to better examine if there is any cryptic diversity within this group.

Figures

Figure 3. Images of preserved Amphidiscophora spongesassociated zoantharians. A, B, Epizoanthus fatuus collected from Japan; C, Epizoanthus aff. fatuus collected from Australia; D, Epizoanthus stellaris collected from Australia; E, Epizoanthus aff. armatus collected from Japan. Scales: 10 mm.