Epizoanthus stellaris, HERTWIG, 1888

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 : 331

EPIZOANTHUS STELLARIS HERTWIG, 1888

( FIG. 3D )

Material examined: QM G337585 . Hunter CMR, New South Wales, Australia, 32°28 ′ 44.4 ″ S –32°30 ′ 25.2 ″ S, 152°59 ′ 27.6 ″ E –52°59 ′ 38.4 ″ E, depth 1006–1036 m, beam trawl, coll. M. Ekins on RV Investigator, Cruise IN2017_V03, 3 June 2017, fixed in 99.5% EtOH .

Description: External morphology. Circa 40 nearly saucer-shaped polyps connected by strongly developed dark-brownish coenenchyme on stalks of hexactinellid sponges ( Hyalonema sp. ) in preserved specimen. Colony covered the upper part of the stalks, but not around the spiculous anchor. Contracted preserved polyps only rise a little from the coenenchyme and flat, 0.4–1.1 mm in height, 3.0– 6.9 mm in diameter. Capitulary ridges present and well pronounced when contracted, approximately 14–18 in number. Ectoderm and mesoglea of polyps and coenenchyme heavily encrusted with numerous sand and silica particles.

Internal morphology. Zooxanthellae absent. Number of mesenteries 28–36, in macrocnemic arrangement. Mesogleal thickness c. 0.1–0.3 mm. Numerous and various size of pigment cells in the ectoderm and mesoglea. Mesoglea thicker than ectoderm and endoderm in column, actinopharynx and mesenteries. Reticulate mesogleal musculature short and poorly developed. Siphonoglyph distinct and V-shaped. Mesenterial filaments present.

Habitat and distribution: Tasman Sea at depths of 1006–1036 m in this study. The type locality of this species is off Samboangan [Zamboanga City], Philippines at a depth of 150 m (82 fathoms). This species has been recorded from the Indian Ocean ( Reimer & Sinniger, 2021), New Zealand ( NIWA, 2018), the East Pacific Ocean ( Beaulieu, 2001; Reimer & Sinniger, 2021) and the Caribbean Sea ( Dueñas & Puentes, 2018).

Associated host: Hyalonema sp.

Remarks: Epizoanthus stellaris can be distinguished from other Epizoanthus species found on stalks of hexactinellid sponges: the strongly lamellated polyps of E. stellaris are not observed in E. fatuus , E. armatus or E. longiceps ( Lwowsky, 1913) (2.0–10.0 mm in height: Lwowsky, 1913; Carlgren, 1923). Lwowsky (1913) synonymized E. stellaris as E. fatuus on account of extreme growth forms of E. fatuus due to the high amounts of morphological variability that are commonly found within zoantharian species. However, the results of our molecular phylogenetic analyses support that E. stellaris and E. fatuus are distinct species. Beaulieu (2001) observed E. stellaris frequently in the East Pacific Ocean, although it should be noted that several species may be contained in E. stellaris , as observed by Beaulieu (2001), based on the results of the present study.

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.