Epizoanthus arenaceus ( Delle Chiaje, 1823 )

Ocaña, Oscar & Çinar, Melih Ertan, 2018, Descriptions of two new genera, six new species and three new records of Anthozoa (Cnidaria) from the Sea of Marmara, Journal of Natural History 52 (35 - 36), pp. 2243-2282 : 2266-2270

Epizoanthus arenaceus ( Delle Chiaje, 1823)

( Figures 15 and 16 )

Epizoanthus arenaceus, Haddon and Shackleton 1891: 649 , Pl. LIX, fig. 7, Pl. LX, fig. 4; Carlgren 1935: 7 – 8, fig. 2; Pax and Müller 1962: 129 – 138, figs 63 – 69; Herbert, 1972: 89 – 94, fig. 1.; Gili et al. 1987: 20 – 21, fig. 2; López-González 1993: 220 – 223, fig. 8.

Material examined

ESFM-CNI/2012-03 ; 02.10 .2012, Sea of Marmara , K18, 40°50 ʹ 26 ʺ N, 29°07 ʹ 33 ʺ E, 15 – 30 m, sandy mud, 8 specimens.

Additional material examined

Ceuta: MMC-338, 5 March 1999, 1 m, in a cave, 30 – 40 retracted specimens, Alborán Sea, O . Ocaña leg .; MMC-339,14/08/1991, Fuentecaballos rocky reefs, 15 specimens with some of them expanded, Alborán Sea, O . Ocaña leg .; MMC-340, 25 May 2000, Piedra Gorda bottoms, growing on maërl algae, 15 – 20 small specimens, Alborán Sea, O . Ocaña leg; MMC-341, 4 September 2000, Las Tres Piedras ( Benzú ), near vertical wall on a loose Stone on seaweeds bottom, 10 specimens attached on hard substrate, Bionomía project, Alborán Sea, O . Ocaña leg .

Description

Small to medium sized zoantharian (in retracted condition, body 5 – 10 mm wide); brownish colour along column, whitish patches on 12 – 15 scapular ridges located in capitulum border ( Figure 15 (a)). Ectodermis of column covered with sand and debris particules. Twenty-five to 35 tentacles arranged in four cycles; 25 – 28 mesenteries arranged in four cycles, last being incomplete. Pharynx lobulated, bearing a single siphonoglyph ( Figure 15 (c)). Single strong mesogloeal enlarged sphincter present ( Figure 15 (b)). Retractor absent, with a very weak parietobasilar development ( Figure 15 (d)). Basal coenenchyme forming a thin stolon with polyps arising together. Coenenchyme expanded.

Cnidom

A survey of the cnidom is summarized in Table 6 and Figure 16 .

Remarks

Epizoanthus arenaceus , which has variable morphological features, has been split up into different subspecies in the Mediterranean Sea. The subspecies can be distinguished from each other based on the sphincter morphology and others (number of tentacles and mesenteries, body wall anatomy and some differences among the cnidom measurements) (see Carlgren 1935; Herbert 1972; Gili et al. 1987). The cnidom features of the Sea of Marmara specimens are closely similar to those of the specimens from the Alborán Sea, thus no consistent evidence is present to distinguish subspecies within the species. The present paper provides a complete cnidom feature of this species. A previous study by López- González (1993) gave descriptive information about the species, but did not indicate two spirulae categories on tentacles, which are clearly evident on the specimens from the Sea of Marmara and Alboran Sea. The rare distribution of penicilli in the tentacles cannot be used to separate E. arenaceus subspecies. Epizoanthus couchii (Johnston in Couch 1844) was recently recorded in the Turkish waters (see Gökalp 2011; Özalp & Ates 2015), but there is no consistent evidence to support these records. It was known that this species does not occur in the Mediterranean Sea ( Häussermann 2003; Coll et al. 2010; Zenetos et al. 2010). In fact, E. couchii shows a morphological similarity with E. arenaceus in terms of its size, colour and habitats, however no detailed description of this species including the cnidom has been documented yet (see Haddon and Shackleton 1891; Manuel 1981). It is well known that nematocysts are important characters to differentiate the zoanhid species ( Carlgren 1913, 1922; Herberts 1972; Schmidt 1974; Ocaña & Brito 2003; Sinniger & Häusserman 2009; Carreiro-Silva et al. 2011, 2017; Sinniger et al. 2013).

Habitat

In the Sea of Marmara , this species was found on shell fragments on sandy mud bottoms at 15 – 30 m depths.

Figures

Figure 15. Epizoanthus arenaceus. (a) Preserved specimens showing the colony structure; (b) sphincter; (c) syphonoglyphs; (d) mesenteries with filaments and weak retractor muscles. Scale bars: a = 7.4 mm, b, c = 1 mm; d = 1.3 mm.

Figure 16. Epizoanthus arenaceus. Cnidom morphology in different parts of the body. (a) Spirocyst; (b) spirulae; (c) spirulae; (d) homotrich; (e) penicilli B; (f) spirulae; (g) spirulae; (h, i) homotrich; (j, k) spirulae; (l, m) homotrich; (n) penicilli A; (o) spirulae; (p, q) homotrich. Scale bar: 13 µm.