Epizoanthus marmarensis, Ocaña & Çinar, 2018

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 : 2270-2273

Epizoanthus marmarensis sp. nov.

( Figures 17 and 18 )

Material examined

Holotype, ESFM-CNI/2013-33 , 23 June 2013, Sea of Marmara , BT- 6, 100 m, start: 40° 55 ʹ 35 ʺ N, 28°30 ʹ 18 ʺ E, finish: 40°54 ʹ 55 ʺ N, 28°31 ʹ 28 ʺ E ; Paratype, ESFM-CNI /2013-34, 23 June 2013, Sea of Marmara , BT- 6, 100 m, start: 40°55 ʹ 35 ʺ N, 28°30 ʹ 18 ʺ E, finish: 40°54 ʹ 55 ʺ N, 28° 31 ʹ 28 ʺ E, 9 specimens.

Description

A small to medium sized, club-shaped zoantharian (in retracted condition, body 25 – 30 mm long, 5 – 10 mm wide); brownish colour along column and whitish patches on 12 – 15 scapular ridges located in upper part of body wall. Column ectodermal, covered with sand and debris particules ( Figure 17 (a)). Twenty-four to 30 tentacles arranged in three or four cycles, last being incomplete. Twenty-five mesenteries arranged in three cycles; 14 complete mesenteries with low diffuse retractors; 10 – 12 microcnemes without any visible muscular or filament developments ( Figure 17 (c)). Pharynx short, lobulated, with a single siphonoglyph ( Figure 17 (d), 17(e)). Retractor absent, with a very weak parietobasilar development. Mesogloeal sphincter concentrated in upper part of body wall, representing a wide zone with more conspicuous muscular development; weak longitudinal musculature along body wall. Basal expansions absent ( Figure 17 (b)). Coenenchyme absent or at least not observed on specimens examined. Polyps arising from a bud, growing on body wall ( Figure 17 (a)).

Cnidom

The morphology of cnidom is summarized in Table 7 and Figure 18 . The small spirulae may be rare, but can be also overlooked due to their tiny size. Spirulae and small homotrichs on filaments were not very common, but perhaps they were unnoticed because of the high amount of eggs found inside the coelenteron. There are no spirulae without short shaft.

Remarks

Many Epizoanthus species develop polyps from a basal coenenchyme or form stolon-like bands with the polyps arising at irregular intervals. The new species described here grows without coenenchyme development and the polyps radiate from a wall budding. Epizoanthus incrustans (= incrustatus) (Düben & Koren 1847) typically grows on shells inhabited by hermit crabs, but exhibits a free form, not well associated with shells. It has elongate polyps radiating from a common central point or bud from shell walls. However, the nature of nematocysts of E. incrustans are different from those of E. marmarensis sp. nov. Large-sized homotrichs on the tentacles and the body wall, and enlarged spirocysts on the tentacles of E. incrustans are absent in E.marmarensis sp. nov. (see Gili et al. 1987). The polyps of E.mediterraneus (elongate, reaching 30 mm in height) grow on mollusc shells and form a basal plate of coenenchyme. The homotrich dimensions especially on tentacles of E. mediterraneus are shorter and narrower than those present on E. marmarensis sp. nov. (see Carlgren 1935). Unlike E.marmarensis sp. nov., E. univittatus (Lorenz 1960) , E. vatovai Pax & Lochter 1935 and E. vagus Herberts 1972 develop short polyps from a common coenenchyme and their homotrichs on tentacles are clearly shorter and narrower (see Herbert 1972; Gili et al. 1987). In particular, the sphincter of E. vagus is weak and developed in the middle of the mesogloea, whereas that of E. marmarensis sp. nov. covers the whole mesogloea width. In addition, E.vagus has much wider spirocysts on tentacles, which are similar to those found in E. incrustans . Epizoanthus tergestinus Pax 1937 , E. steueri Pax 1937 and E. frenzeli Pax 1937 were originally described from the Adriatic Sea ( Pax and Müller 1962). The lack of detailed information and figures of the species in the Pax ’ s descriptions resulted in confusion with the other Epizoanthus species known in the region, therefore Gili et al. (1987) considered the Pax ’ s species as doubtful. Gili et al. (1987) recognized the possibility of presence of subspecies within the genus Epizoanthus with relation to habitats they occupy. Epizoanthus marmarensis sp. nov. is quite different from any other Mediterranean species of Epizoanthus because of the following characters: (1) there is no visible stolon or basal plate in E. marmarensis sp. nov., but there is only budding from the polyp walls; (2) there is no spirulae (b-mastigophore) with short shafts; (3) The longitudinal musculature of the column of E. marmarensis sp. nov. is very weak, which hinders the retraction of specimens; (4) the measurements of the homotrichs on tentacles and body walls. The absence of the spirulae with short shafts is a distinguishing character of E. marmarensis sp. nov. when compared to other species of ‘ Zoantharia ’ (sensu Schmidt 1974: 544, there are two groups of zoantharia based on the cnidae categories). As far as we know that there is no Epizoanthus species without short shafted spirulae; at least not in the European waters and the Mediterranean Sea (see Carreiro-Silva et al. 2017); information from others temperate waters indicate the presence of short shafted spirulae in Epizoanthus species (see Sinniger and Häussermann 2009).

Habitat

This species was only found in muddy bottom at 100 m depth.

Etymology

The species name refers to the type locality.

Figures

Figure 17. Epizoanthus marmarensis sp. nov. (a) General views of live specimens; (b) longitudinal section showing the mesogleal sphincter; (c) longitudinal section showing the general disposition of the mesenteries and tentacles; (d) transversal section showing trilobulated filaments and syphonoglyphs; (e) a close up view of transversal section. Scale bar: a = 1.3 mm, b = 1.4 mm, c = 0.90 mm, d = 0.88 mm, e = 0.56 mm.

Figure 18. Epizoanthus marmarensis sp. nov. Cnidom morphology in different parts of the body. (a) Spirocyst; (b) spirulae; (c, d) homotrich; (e, f) spirulae; (g) penicilli A; (h, i) homotrich; (j, k) spirulae; (l) penicilli A; (m–p) homotrich. Scale bar: 13 µm.