Diadumene turcica, 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 : 2252-2256

Diadumene turcica sp. nov.

( Figures 7 and 8 )

Material examined

Holotype; ESFM-CNI/2013-18 , Sea of Marmara , 18 June 2013, DT-6, start: 40°45 ʹ 28 ʺ N, 28°53 ʹ 35 ʺ E, finish: 40°48 ʹ 53 ʺ N, 28°25 ʹ 49 ʺ E, 1200 m, on a disposal stell scrap, cross sectioned for anatomical purposes . Paratype; ESFM-CNI /2013-19, Sea of Marmara , 18 June 2013, DT-6, start: 40°45 ʹ 28 ʺ N, 28°53 ʹ 35 ʺ E, finish: 40°48 ʹ 53 ʺ N, 28°25 ʹ 49 ʺ E, 1200 m, on a disposal stell scrap, 0.2 – 0.5 cm × 0.2 – 0.4 cm, on a disposal stell scrap, 3 specimens.

Description

In preserved specimens, colour pale brown, base irregular in outline. In live specimens, colour whitish, with dark reddish pigmentation at base of each tentacle ( Figure 7 ). Column with scapulus (just thin part of column ’ s ectoderm previous to capitulum) and scapus (most of body wall ectoderm). Four pointed tentacle cycles observed in specimens, but last cycle being incomplete: 6 + 6 + 12 + 24. Four cycles of mesenteries: two perfect mesenteries; third one being incomplete with low development retractors; last one having incomplete microcnemes without any trace of retractors: 6 + 6 + 12 + 24, with a total of 28 or 30 observed mesenteries. Ova observed in most mesenteries. Pharynx occupied 40 – 50% of column length; two siphonoglyphs. Thin mesogloea along column. Well-developed ectoderm with numerous conspicuous folders. No sphincter; tentacles with weak ectodermal musculature, but with well-developed endodermic musculature. Parietobasilar muscle observed in all mesenteries; restringed reniform retractors stronger in macrocneme mesenteries; in any case only occupied central part of mesenteries.

Cnidom

A survey of the cnidom is summarized in Table 2. Abundant acontiae were mixed up with the filaments, so many acontia capsules were found on the filaments. Large penicilli B is present in the ectoderm of the body wall ( Figure 8 ). Tiny penicilli B is also sporadically observed in the acontiae. Sporadic penicilli A and large spirulae similar to

those found in the tentacles can be observed in the pharynx. Penicilli A is present, but scarce in the filaments.

Remarks

The genus Diadumene has many species widely distributed in the world ’ s oceans. Diadumene cincta Stephenson 1925 , a north Atlantic species, was also found in the Mediterranean and Sea of Marmara (also observed in the present study). Diadumene lineata ( Verrill 1869) has been recorded in both hemispheres with a wide geographical distribution and seems apparently to be absent in the poles. The species in this genus might tolerate extreme temperature and salinity variations so they also occur typically in brackish waters (see Birkemeyer 1996), and were also transferred from one area to another via shipping ( Zenetos et al. 2012). The internal anatomy is quite similar among Diadumene species , but there are some characters (e.g. types of nematocysts) that are different. For example, catch tentacles are present in D. cincta , but they are absent in D. turcica sp. nov. In addition, in normal tentacles, D. cincta has bigger penicilli but smaller spirulae than those present in D. turcica sp. nov. Two types of penicilli are present in the pharynx of D. cincta , but only one in D. turcica sp. nov. (see Carlgren 1940; Ocaña 1994; Birkemeyer 1996). There are two categories of penicilli in acontia and tentacles in D. lineata , but there is only one category in D. turcica sp. nov. Diadumene turcica sp. nov. has two types of spirulae in tentacles, but D. lineata has only one type in tentacles (see Hand 1956). Diadumene franciscana Hand 1956 and D. lighti Hand 1956 , which were originally described from the California (see Hand 1956), inhabit the shallow- and brackish-water benthic environments. Diadumene leucolena ( Verrill 1866) is another Pacific species found in intertidal and shallow waters (see Hand 1956; Ocaña & Hartog 2002; Ocaña et al. 2015). Diadumene schilleriana ( Stoliczka 1869) inhabits the Chilka Lake in India. Diadumene neozelanica Carlgren 1924 is also a shallow water species found in some pristine areas of the New Zealand (see Ocaña 1997). Diadumene paranaensis Beneti, Stampar, Maronna, Morandini, Da Silveira 2015 has been recently described from the Brazilian brackish waters (see Beneti et al. 2015). The new species presented here, Diadumene turcica sp. nov., is the only species of this genus that occurs in deep waters (1200 m). In addition to the difference in the depth preferences of the above-mentioned Diadumene species , D. leucolena and D. franciscana have wider and larger penicilli on the acontia than those in D. turcica sp. nov.; D. lineata , D. cincta and D. lighti have smaller spirulae on the acontia, whereas D. turcica sp. nov. has larger and wider spirulae on the acontia; D. neozelanica , which can unusually reach a larger body size (6 – 8 cm in diameter), has larger penicilli on the acontia when compared to those in D. turcica sp. nov. (see Carlgren 1924). Another large-sized species Diadumene schilleriana has catch tentacles that are absent in D. turcica sp. nov. The cnidom morphology of D. paranaensis is very different from that in D. turcica sp. nov., as the former species include large nematocysts on the catch tentacles; penicilli rarely distributed in the actinopharynx; and two categories of large penicilli on the acontia.

Habitat

This species was found in the deepest part of the Sea of Marmara , at Çinarcik Basin (1200 m), attached on an iron piece thrown into the sea.

Etymology

The species name is dedicated to type locality of the species, Turkey .

Figures

Figure 7. Diadumene turcica sp. nov. Oral view of a live specimen. Scale bar: 1 mm.

Figure 8. Diadumene turcica sp. nov. Cnidom morphology in different parts of the body. (a) Spirocyst; (b) penicilli B; (c) spirulae 1; (d) spirulae 2; (e) spirulae; (f) penicilli A; (g) penicilli B; (h) penicilli B1; (i) penicilli B2; (j) penicilli A; (k) spirulae; (l) spirulae 1; (m) spirulae 2; (n) penicilli B; (o) homotrich; (p) penicilli B1; (q) penicilli B2; (r) spirulae 1; (s) spirulae 2. Scale bar: 13 µm.